Dissertations / Theses: 'Species niche'

1

Janse, Van Vuuren Adriaan. "Niche Occupation in Biological Species Competition." Thesis, Stellenbosch : University of Stellenbosch, 2008. http://hdl.handle.net/10019.1/2932.

Full text

Abstract:

Thesis (MSc (Logistics))--University of Stellenbosch, 2008.
The primary question considered in this study is whether a small population of a biological species introduced into a resource-heterogeneous environment, where it competes for these resources with an already established native species, will be able to invade successfully. A two-component autonomous system of reaction-diffusion equations with spatially inhomogeneous Lotka-Volterra competitive reaction terms and diffusion coefficients is derived as the governing equations of the competitive scenario. The model parameters for which the introduced species is able to invade describe the realized niche of that species. A linear stability analysis is performed for the model in the case where the resource heterogeneity is represented by, and the diffusion coefficients are, two-toned functions. In the case where the native species is not directly affected by the resource heterogeneity, necessary and sufficient conditions for successful invasion are derived. In the case where the native species is directly affected by the resource heterogeneity only sufficient conditions for successful invasion are derived. The reaction-diffusion equations employed in the model are deterministic. However, in reality biological species are subject to stochastic population perturbations. It is argued that the ability of the invading species to recover from a population perturbation is correlated with the persistence of the species in the niche that it occupies. Hence, invasion time is used as a relative measure to quantify the rate at which a species’ population distribution recovers from perturbation. Moreover, finite difference and spectral difference methods are employed to solve the model scenarios numerically and to corroborate the results of the linear stability analysis. Finally, a case study is performed. The model is instantiated with parameters that represent two different cultivars of barley in a hypothetical environment characterized by spatially varying water availability and the sufficient conditions for successful invasion are verified for this hypothetical scenario.

APA, Harvard, Vancouver, ISO, and other styles

2

Janse, van Vuuren Adriaan. "Niche occupation in biological species competition /." Link to the online version, 2008. http://hdl.handle.net/10019/753.

Full text

APA, Harvard, Vancouver, ISO, and other styles

3

Dutrieux, Mariane. "Spatio-temporal species distribution modeling: Application to invasive alien species’ monitoring." Thesis, KTH, Hållbar utveckling, miljövetenskap och teknik, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-224319.

Full text

Abstract:

The developments of species distribution modeling techniques have brought new opportunities in the field of biological invasion management. In particular, statistical niche modeling for spatio-temporal predictions of species’ distribution is a widely spread tool that has proved its efficiency. The main purpose of this Master thesis is to study applicability of species distribution modeling to invasive alien species, with the aim of supporting efficient decision-making for their prevention. Some research questions are: how useful can species distribution modeling be for invasives’ prevention? Is distribution modeling technically feasible in the case of invasive species? What types of techniques are recommended to model distributions of IAS? What are the limits of such a tool? The methods employed to answer these questions are literature review and expert advice. I found that species distribution models can provide risk maps which are necessary to enable effective invasive alien species’ prevention. However intrinsic characteristics of invasives introduce uncertainties in the predictions made. Consequently several preliminary analyses should be conducted before applying the distribution model. Finally recommendations were made on the most appropriate distribution modeling technique to use depending on the urgency of the situation and the availability of data.
Utvecklingen av metoder för modelering av artdistribution har medfört nya möjligheter inom området hantering av biologiska invasioner. Statistisk nischmodelering för spatio-temporala förutsägelser av arters distribution är ett väl använt verktyg som har visat sig vara effektivt. Det övergripande målet med det här arbetet har varit att studera hur lämpad artmodelering är vid förebyggande av invasioner av främmande arter. Det har även undersökts huruvida metoden kan bidra till bättre och enklare beslutsfattande när det kommer till att förhindra sådana invasioner. Forskningsfrågorna lyder: hur användbart är fördelningsmodelering för förebyggande av spriding av invasiva arter? Är distributionsmodelering tekniskt genomförbar när det gäller invasiva arter? Vilka olika tekniker rekommenderas för att modelera spridningen av invasiva arter? Vilka begräsningar har modelerna? De metoder som används är litteraturöversikt och expertråd. Resultaten visar att artdistributionsmodelering kan bidra till att sammanställa riskkartor som är nödvändiga för att möjliggöra ett förebyggande arbete. Men speciella egenskaper hos de invasiva arterna som är svåra att förutse skapar osäkerheter i resultatet. Därför kan preliminära analyser med fördel genomföras innan modelering. I slutsatserna återfinns rekommendationer för vilken distributionsmodelteknik man bör använda, beroende av hur brådskande situationen är och om data finns tillgängligt.

APA, Harvard, Vancouver, ISO, and other styles

4

McHugh, Sean W. "Phylogenetic Niche Modeling." Thesis, Virginia Tech, 2021. http://hdl.handle.net/10919/104893.

Full text

Abstract:

Projecting environmental niche models through time is a common goal when studying species response to climatic change. Species distribution models (SDMs) are commonly used to estimate a species' niche from observed patterns of occurrence and environmental predictors. However, a species niche is also shaped by non-environmental factors--including biotic interactions and dispersal barrier—truncating SDM estimates. Though truncated SDMs may accurately predict present-day species niche, projections through time are often biased by environmental condition change. Modeling niche in a phylogenetic framework leverages a clade's shared evolutionary history to pull species estimates closer towards phylogenetic conserved values and farther away from species specific biases. We propose a new Bayesian model of phylogenetic niche implemented in R. Under our model, species SDM parameters are transformed into biologically interpretable continuous parameters of environmental niche optimum, breadth, and tolerance evolving under multivariate Brownian motion random walk. Through simulation analyses, we demonstrated model accuracy and precision that improved as phylogeny size increased. We also demonstrated our model on a clade of eastern United States Plethodontid salamanders by accurately estimating species niche, even when no occurrence data is present. Our model demonstrates a novel framework where niche changes can be studied forwards and backwards through time to understand ancestral ranges, patterns of environmental specialization, and niche in data deficient species.
Master of Science
As many species face increasing pressure in a changing climate, it is crucial to understand the set of environmental conditions that shape species' ranges--known as the environmental niche--to guide conservation and land management practices. Species distribution models (SDMs) are common tools that are used to model species' environmental niche. These models treat a species' probability of occurrence as a function of environmental conditions. SDM niche estimates can predict a species' range given climate data, paleoclimate, or projections of future climate change to estimate species range shifts from the past to the future. However, SDM estimates are often biased by non-environmental factors shaping a species' range including competitive divergence or dispersal barriers. Biased SDM estimates can result in range predictions that get worse as we extrapolate beyond the observed climatic conditions. One way to overcome these biases is by leveraging the shared evolutionary history amongst related species to "fill in the gaps". Species that are more closely phylogenetically related often have more similar or "conserved" environmental niches. By estimating environmental niche over all species in a clade jointly, we can leverage niche conservatism to produce more biologically realistic estimates of niche. However, currently a methodological gap exists between SDMs estimates and macroevolutionary models, prohibiting them from being estimated jointly. We propose a novel model of evolutionary niche called PhyNE (Phylogenetic Niche Evolution), where biologically realistic environmental niches are fit across a set of species with occurrence data, while simultaneously fitting and leveraging a model of evolution across a portion of the tree of life. We evaluated model accuracy, bias, and precision through simulation analyses. Accuracy and precision increased with larger phylogeny size and effectively estimated model parameters. We then applied PhyNE to Plethodontid salamanders from Eastern North America. This ecologically-important and diverse group of lungless salamanders require cold and wet conditions and have distributions that are strongly affected by climatic conditions. Species within the family vary greatly in distribution, with some species being wide ranging generalists, while others are hyper-endemics that inhabit specific mountains in the Southern Appalachians with restricted thermal and hydric conditions. We fit PhyNE to occurrence data for these species and their associated average annual precipitation and temperature data. We identified no correlations between species environmental preference and specialization. Pattern of preference and specialization varied among Plethodontid species groups, with more aquatic species possessing a broader environmental niche, likely due to the aquatic microclimate facilitating occurrence in a wider range of conditions. We demonstrated the effectiveness of PhyNE's evolutionarily-informed estimates of environmental niche, even when species' occurrence data is limited or even absent. PhyNE establishes a proof-of-concept framework for a new class of approaches for studying niche evolution, including improved methods for estimating niche for data-deficient species, historical reconstructions, future predictions under climate change, and evaluation of niche evolutionary processes across the tree of life. Our approach establishes a framework for leveraging the rapidly growing availability of biodiversity data and molecular phylogenies to make robust eco-evolutionary predictions and assessments of species' niche and distributions in a rapidly changing world.

APA, Harvard, Vancouver, ISO, and other styles

5

Khondkaryan, Lusine. "Ecological niche modeling of rodent and flea species /." [Sedeh Boker, Israel] : Ben-Gurion University of the Negev, 2008. http://aranne5.lib.ad.bgu.ac.il/others/KhondkaryanLusine.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

6

Vergnon, Remi. "Testing niche-based and neutral mechanisms of species coexistence." Thesis, University of Sheffield, 2010. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.527228.

Full text

APA, Harvard, Vancouver, ISO, and other styles

7

Brown, Michael Scott. "A Species-Conserving Genetic Algorithm for Multimodal Optimization." NSUWorks, 2010. http://nsuworks.nova.edu/gscis_etd/104.

Full text

Abstract:

The problem of multimodal functional optimization has been addressed by much research producing many different search techniques. Niche Genetic Algorithms is one area that has attempted to solve this problem. Many Niche Genetic Algorithms use some type of radius. When multiple optima occur within the radius, these algorithms have a difficult time locating them. Problems that have arbitrarily close optima create a greater problem. This paper presents a new Niche Genetic Algorithm framework called Dynamic-radius Species-conserving Genetic Algorithm. This new framework extends existing Genetic Algorithm research. This new framework enhances an existing Niche Genetic Algorithm in two ways. As the name implies the radius of the algorithm varies during execution. A uniform radius can cause issues if it is not set correctly during initialization. A dynamic radius compensates for these issues. The framework does not attempt to locate all of the optima in a single pass. It attempts to find some optima and then uses a tabu list to exclude those areas of the domain for future iterations. To exclude these previously located optima, the framework uses a fitness sharing approach and a seed exclusion approach. This new framework addresses many areas of difficulty in current multimodal functional optimization research. This research used the experimental research methodology. A series of classic benchmark functional optimization problems were used to compare this framework to other algorithms. These other algorithms represented classic and current Niche Genetic Algorithms. Results from this research show that this new framework does very well in locating optima in a variety of benchmark functions. In functions that have arbitrarily close optima, the framework outperforms other algorithms. Compared to other Niche Genetic Algorithms the framework does equally well in locating optima that are not arbitrarily close. Results indicate that varying the radius during execution and the use of a tabu list assists in solving functional optimization problems for continuous functions that have arbitrarily close optima.

APA, Harvard, Vancouver, ISO, and other styles

8

Swisher, Robert E. "Paleobiogeographical and evolutionary analysis of Late Ordovician, C₅ sequence brachiopod species, with special reference to Rhynchonellid taxa." Ohio : Ohio University, 2009. http://www.ohiolink.edu/etd/view.cgi?ohiou1245445583.

Full text

APA, Harvard, Vancouver, ISO, and other styles

9

Swisher, Robert E. "Paleobiogeographical and Evolutionary Analysis of Late Ordovician, C5 Sequence Brachiopod Species, with Special Reference to Rhynchonellid Taxa." Ohio University / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1245445583.

Full text

APA, Harvard, Vancouver, ISO, and other styles

10

Gamboa, Badilla Nancy. "The role of species niche, species dispersal and landscape factors in the assembly of novel woody communities in metropolitan Mediterranean regions." Doctoral thesis, Universitat de Barcelona, 2017. http://hdl.handle.net/10803/462039.

Full text

Abstract:

Biological diversity in a global scale has been threaten seriously by anthropogenic disturbances in ecosystems. Changes in land cover and land use affect biodiversity, causing habitat loss and species extinction, or colonization and establishment of new communities. Such effects could happen in an outdated way between the time of the disturbance and species extinction or colonization. Landscape history, connectivity between habitat fragments and the dispersion of organism, shapes species diversity and influences extinction and colonization process. On the other hand, exotic plant invasion could drive the assembly of plant community in newly formed forests as a result of changes in land use. The present thesis aims to contribute to the knowledge of the assembly of new woody communities in forests and bushes of the metropolitan region of Barcelona. For this, the legacy of five historical land use trajectories and the environmental factors on the richness, diversity and equity of woody species in shrubland were analyzed. In addition, we evaluated the relationship between environmental and historical factors and species composition (Chapter 3). The results revealed that species richness and diversity are associated with both elevation and historical trajectories of land use, while equity only to elevation. The study did not detect spatial effects attributable to dispersion. The results indicated that both trajectories and environmental factors (niche) equally drive local community assembly, while dispersal seems to play a secondary role. The richness and diversity of species are affected by the use of the soil in the recent past (1956) and the composition by the oldest uses (1900). Additionally, the effect of urbanization on plant community assembly process in new periurban forests (Chapter 4) was evaluated. We explored the relationship between plant species richness and composition (dispersed by vertebrates and non-vertebrates), and forest patches history (pre-existing and recent), landscape pattern (forest connectivity and urbanization), habitat condition (forest, prairie grass, synanthropic, other) and environmental variables. The results showed that landscape habitat and structure are the main drivers of plant community assembly. However, as a side effect of forest history, extinction debt of scrub-meadow species must be considered. In addition, we found a greater colonization of synanthropic species and a credit for colonization of forest species dispersed by vertebrates in recent forests. The assemblage of new forests was characterized by the presence of species of previous habitats, rapid colonization of specialists and an increase of synanthropic species. Finally, the patterns of invasion by exotic plants and the influence of dispersal mechanism, environmental variables and landscape anthropization in these newly formed periurban forests were analyzed (Chapter 5). The presence, richness and abundance of exotic species dispersed by vertebrates and non - vertebrates in recent and preexisting forests were compared, taking into account landscape and environmental correlations. The results showed that metropolitan forests are more invaded than the rest of the province and the exotic flora on these forests are dominated by species dispersed by vertebrates. However, at the regional level a bias was found towards species dispersed by non-vertebrates. Forest fragmentation was associated with the presence, richness and coverage of plants dispersed by vertebrates; while urbanization was related with coverage of species dispersed by non-vertebrates. We suggest an association between forest history and plant dispersion syndromes, with species dispersed by vertebrates in ancient forests. No associations between exotic species composition and environmental factors were found, but not with forest history. The study notes a high degree of invasion of forests by alien species dispersed by vertebrates, which could colonize unaltered forests and persist and even expand throughout forest succession.
Las alteraciones antrópicas en los ecosistemas amenazan gravemente la diversidad biológica a escala global. Cambios en las cubiertas y usos del suelo afectan la biodiversidad, causando pérdida de hábitats y extinción de especies o bien colonización y establecimiento de especies que forman nuevas comunidades. Tales efectos podrían suceder de forma desfasada entre el momento de la perturbación y la extinción o colonización de las especies. Podrían además verse condicionados por la historia del paisaje, que influye sobre la diversidad de las especies, la conectividad entre fragmentos de hábitat y la dispersión de los organismos. Por otra parte, la invasión por plantas exóticas podría conducir el ensamblaje de la comunidad vegetal en bosques recién formados, como resultado de cambios en el uso de la tierra. La presente tesis tiene como objetivo aportar al conocimiento del ensamblaje de las nuevas comunidades leñosas en bosques y matorrales de la región metropolitana de Barcelona. Para ello se analizó el legado de cinco trayectorias históricas del uso del suelo y los factores ambientales sobre la riqueza, diversidad y equidad de especies leñosas en matorrales. Además, se evaluó la relación entre los factores ambientales e históricos y la composición de las especies (Capítulo 3). Los resultados revelaron que la riqueza y diversidad de estas especies se asocia tanto a la elevación como a las trayectorias históricas del uso de la tierra, mientras que la equidad sólo a la elevación. El estudio no detectó efectos espaciales atribuibles a la dispersión. Los resultados indicaron que tanto las trayectorias como los factores ambientales (nicho) impulsan de igual forma el ensamblaje de la comunidad a escala local, mientras que la dispersión parece desempeñar un papel secundario. La riqueza y diversidad de especies son afectadas por el uso del suelo en el pasado reciente (1956) y la composición por los usos más antiguos (1900). Por otra parte, se evaluó el efecto de la urbanización sobre el proceso de ensamblaje de las comunidades vegetales en los nuevos bosques periurbanos (Capítulo 4). Se exploró la relación entre la historia de parches forestales (preexistentes y recientes), el patrón del paisaje (conectividad forestal y urbanización), la condición del hábitat (bosque, matorral-pradera, sinantrópico, otro) y las variables ambientales con la riqueza y composición de las especies de plantas (dispersadas por vertebrados y no vertebrados). Los resultados mostraron que el hábitat y la estructura del paisaje son los principales impulsores del ensamblaje de la comunidad vegetal. Sin embargo, hay un efecto secundario de la historia del bosque, constituido por la deuda de extinción de especies de matorral-pradera. Además, se encontró una mayor colonización de especies sinantrópicas y un crédito de colonización de especies forestales dispersadas por vertebrados en los bosques recientes. El ensamblaje de bosques nuevos se caracterizó por la presencia de especies de hábitats anteriores, rápida colonización de especialistas y un aumento de especies sinantrópicas. Finalmente, se analizaron los patrones de invasión por plantas exóticas y la influencia del mecanismo de dispersión, las variables ambientales y la antropización del paisaje en estos bosques periurbanos recién formados (Capítulo 5). Se comparó la presencia, la riqueza y la abundancia de especies exóticas dispersadas por vertebradas y no vertebradas en bosques recientes y preexistentes, teniendo en cuenta las correlaciones paisajísticas y ambientales. Los resultados mostraron que los bosques metropolitanos están más invadidos que los del resto de la provincia y la flora exótica en estos bosques está dominada por especies dispersadas por vertebrados. Sin embargo, a nivel regional se encontró un sesgo hacia las especies dispersadas por no vertebrados. La fragmentación de los bosques se asoció con la presencia, riqueza y cobertura de plantas dispersadas por vertebrados; mientras que la urbanización con la cobertura de especies dispersadas por no vertebrados. Se sugiere una asociación entre la historia de los bosques y los síndromes de dispersión de las plantas, con especies dispersadas por vertebrados en bosques antiguos. No se detectaron asociaciones entre la historia del bosque y la composición de especies exóticas, sí con factores ambientales. El estudio advierte alto grado de invasión de bosques por especies exóticas dispersadas por vertebrados, las cuales podrían colonizar bosques inalterados y persistir e incluso expandirse a lo largo de la sucesión.

APA, Harvard, Vancouver, ISO, and other styles

11

Pender, Jocelyn E. "Climatic Niche Estimation, Trait Evolution and Species Richness in North American Carex (Cyperaceae)." Thesis, Université d'Ottawa / University of Ottawa, 2016. http://hdl.handle.net/10393/34334.

Full text

Abstract:

With close to 2100 species, the flowering plant genus Carex (Cyperaceae; sedges) is an example of an evolutionary radiation. Despite its potential for use as a model taxon in evolutionary studies, the diversification of sedges remains largely unexplored. This thesis realizes the potential of Carex as an evolutionary model group by using it to ask questions about species richness patterns. More specifically, it seeks to determine the relationship, if any, between rates of trait evolution and species richness. This tests the hypothesis that organisms with increased abilities to evolve new traits, speciate more rapidly. Morphological and ecological (habitat and climatic niche) traits are modelled on a nearly complete regional (North America north of Mexico) phylogeny and rates of trait evolution are compared among non-nested sister groups. However, before trait evolution is modelled, this work evaluates the sensitivity of climatic niche estimates to underlying distribution datasets. It tests the agreement of niche estimates derived from the commonly used online repository GBIF (the Global Biodiversity Information Facility) and county-level distributions via BONAP (the Biota of North America Program). Results showed that in the context of phylogenetic comparative analyses, it is not vital to obtain highly accurate climatic niche estimates. The second study found significant positive correlations between the rates of climatic niche, habitat and reproductive morphological evolution and species richness. This result supports the role of high trait lability in generating species richness and more generally, the idea that high trait disparity through evolutionary time leads to species success.

APA, Harvard, Vancouver, ISO, and other styles

12

Malizia, Richard Walter. "Analyzing Niche Stability in Late Ordovician Articulated Brachiopod Species during the Richmondian Invasion." Ohio University / OhioLINK, 2011. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1305225406.

Full text

APA, Harvard, Vancouver, ISO, and other styles

13

Pérez, Navarro Maria Ángeles. "Plant species climatic niche and its relationship with population responses to extreme drought." Doctoral thesis, Universitat Autònoma de Barcelona, 2020. http://hdl.handle.net/10803/669559.

Full text

Abstract:

Understanding how climate affects species’ distribution and performance is a central issue in ecology since its origins. In last decades, however, the interest in this question has been reactivated by the current context of climate change. Species Niche Modelling has been widely used to assess shifts in species distribution and to test the relationship between species’ climatic niche and species physiological and demographic performance. Nevertheless it is still largely undetermined whether these models can portray population and community responses, particularly in relation to extreme climatic episodes. In this thesis I aim at exploring the capacity of niche modelling to predict species decay under extreme climatic conditions, particularly droughts, addressing some constraints of this approach and proposing possible solutions. To achieve this goal, I counted with 3 vegetation decay datasets measured in the Spanish SE after the extreme drought year 2013-2014. In the second chapter I used different Species Distribution Model (SDMs) algorithms to estimate species’ climatic suitability before (1950-2000) and during the extreme drought, in order to test the possible correlation between suitability and decay, and whether the existence of this relationship depended on the applied SDM algorithm. I consistently found a positive correlation between remaining green canopy and species’ climatic suitability before the event, suggesting that populations historically living closer to their species’ tolerance limits are more vulnerable to drought. Contrastingly, decreased climatic suitability during the drought period did not correlate with remaining green canopy, likely because of extremely low climatic suitability values achieved during the exceptional climatic episode. In order to test whether this extremely low suitability values could derive as a consequence of only considering climatic averages when calibrating SDMs, in the thired chapter I developed a method to include inter-annual climatic variability into niche characterization. I then compared the respective capacities of climatic suitabilities obtained from averaged-based and from inter-annual variability-based niches to explain demographic responses to extreme climatic events. I found that climatic suitability obtained from both niches quantifications significantly explained species demographic responses. However, climatic suitability from inter-annual variability-based niches showed higher explanatory capacity, especially for populations that tend to be more geographically marginal. In the fourth chapter I tried to overcome the inability of the SDMs to predict populations decay during extreme conditions, by using Euclidean distances to species’ niche in the environmental space. I compared the capacities of both population distances in the climatic environmental space and population climatic suitability derived from SDMs to explain population observed demographic responses to an extreme event. I found that SDMs-derived suitability failed to explain population decay while distances to the niche centroid and limit significantly explained population die-off, highlighting that population displaced farther from species’ niche during the extreme episode showed higher vulnerability to drought. In the fifth chapter, I used species niche characterizations in the environmental space and demographic data to address the impact of extreme events at community level. Particularly, I estimated the community climatic disequilibrium before and after a drought episode. I found that extreme drought nested within a decadal trend of increasingly aridity led to a reduction in community climatic disequilibrium.

APA, Harvard, Vancouver, ISO, and other styles

14

Smith, Tyler William. "Species limits, phylogeny and niche evolution: a case study in «Carex» (Cyperaceae)." Thesis, McGill University, 2007. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=18468.

Full text

Abstract:

Two conflicting processes are believed to influence the relationship between taxonomic and ecological diversity: adaptive radiation and niche conservatism. No consensus has yet emerged regarding the conditions that favour conservatism of traits due to common ancestry over adaptive radiation and the resulting ecological divergence. Carex is an ideal group for studying these phenomena, as it is incredibly diverse taxonomically and ecologically, and includes many recently formed lineages. I chose a group of eight closely related Carex taxa from eastern North America as the focus of my study. Multivariate analysis of 30--33 morphological variables measured on 456 plants from 110 populations confirmed the existence of eight different entities. Analysis of 141 AFLP fragments from 435 plants from the same populations revealed the same eight groups. I recognise each of these taxa as distinct species. These include C. roanensis, a globally rare species whose taxonomic status had been questioned, and C. complanata and C. hirsutella, a pair of species that some authors had considered a single variable taxon. Six previously unknown sterile or nearly sterile hybrids are documented with a combination of morphology, restriction fragment, and AFLP data. Parsimony and distance analyses of the AFLP data failed to fully resolve the phylogeny of this group, but did establish consistent estimates of the relative evolutionary distances among species. Morphology does not reflect the phylogenetic relationships in this group. There were significant differences among species for niche measures calculated from climate variables, ecological niche models, and local habitat variables. Niche divergence was significantly correlated with phylogenetic distance, indicating niche conservatism is an important process governing ecological evolution in this group. Furthermore, the shape of the relationship suggested that phylogenetic distance limits the maximum possible ecological divergence, but with
Deux processus conflictuels influenceraient la relation entre la diversité taxonomique et écologique: la radiation adaptative et le conservatisme de niche. Aucun consensus n'a encore émergé quant aux conditions qui favorisent le conservatisme de traits par ascendance commune plutôt que la radiation adaptative et la divergence écologique qui en résulte. Le genre Carex est le groupe idéal pour étudier ces phénomènes, étant incroyablement diversifié aux plans taxonomique et écologique et incluant plusieurs lignées récemment formées. J'ai choisi un groupe de huit taxons étroitement reliés de Carex de l'Est de l'Amérique du Nord pour mon étude. Des analyses multivariées de 30--33 variables morphologiques, mesurées sur 456 plants provenant de 110 populations, ont confirmé l'existence de huit entités. L'analyse de 141 fragments AFLP de 435 plants des mêmes populations a révélé les mêmes huit groupes. Je reconnais chacun de ces taxons comme étant une espèce distincte. Ces espèces incluent C. roanensis, une espèce globalement rare dont le statut taxonomique a été questionné, ainsi que C. complanata et C. hirsutella, une paire d'espèce que certains auteurs avaient considéré comme un seul taxon variable. Six hybrids stériles ou presque auparavant inconnus sont documentés avec une combinaison de morphologie, de fragments de restriction et de données AFLP. Les analyses de parcimonie et de distance n'ont pu résoudre entièrement la phylogénie de ce groupe mais ont pu établir des estimés cohérents des distances évolutives relatives entre les espèces. La morphologie ne reflète pas les relations phylogénétiques de ce groupe. Il y avait des différences significatives entre les espèces pour les mesures de niche calculées à partir de variables climatiques, de modèles de niche écologique et de variables de l'habitat local. La divergence de niche était significativement corrélée à la distance phylogénétique, identifian

APA, Harvard, Vancouver, ISO, and other styles

15

FitzGerald, Alyssa. "Speciation and Ecological Niche Divergence of a Boreal Forest Bird Species Complex." Thesis, State University of New York at Albany, 2017. http://pqdtopen.proquest.com/#viewpdf?dispub=10276556.

Full text

Abstract:

Evolutionary biologists are supremely interested in the events that cause populations to diverge and speciate, and the mechanisms that maintain divergence over time. Here, I investigate the evolutionary history of a boreal bird species complex. Boreal bird species are co-distributed, diverged during the Pleistocene, and generally have patterns of genetic divergence that are consistent with a single “boreal” clade in northern and eastern North America. The Gray-cheeked Thrush species complex, however, shows a possible species break in eastern North America between the Bicknell’s Thrush ( Catharus bicknelli) and Gray-cheeked Thrush (Catharus minimus ). Using population genetic and genomic analyses of the largest sampling to-date of either species, I find that the eastern break indeed coincides with a species-level divergence, although low levels of admixture in a few individuals and one probable hybrid hint at the possibility of occasional hybridization. Species distribution models (SDMs) of the Last Glacial Maximum revealed that divergence may have been maintained by residence in different late-Pleistocene refugia. However, because speciation occurred mid-Pleistocene, I examined the geographical context of divergence of the Bicknell’s Thrush and Gray-cheeked Thrush using multivariate analyses and ecological niche modeling techniques of local-scale habitat data and broad-scale climate and tree species distributions. Local-scale habitat analyses reveal that the thrushes breed at sites with unique tree species composition, physiognomy (forest structure), and ground cover characteristics; furthermore broad-scale analyses reveal that niche divergence, rather than conservatism, was the predominant pattern for these species, suggesting that ecological divergence has played a role in their speciation. This dissertation supports the hypothesis that the Bicknell’s Thrush and Gray-cheeked Thrush are distinctive species that breed in divergent local- and broad-scale niches and emphasizes that this species-level divergence seems unique among boreal bird species.

APA, Harvard, Vancouver, ISO, and other styles

16

Stenberg, Christofer. "Co-evolving niches in virtual Plant species : Exploring the niche forming capabilities of coevolving plants in a virtual environment." Thesis, Högskolan i Skövde, Institutionen för kommunikation och information, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:his:diva-6379.

Full text

APA, Harvard, Vancouver, ISO, and other styles

17

MarcoÌ, AÌ€urea Peralba. "Niche separation of Clausocalanus species in the Mediterranean Sea and in the Atlantic Ocean." Thesis, Open University, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.446096.

Full text

APA, Harvard, Vancouver, ISO, and other styles

18

Walls, Bradley J. "Quantitative Paleobiogeography of Maysvillian (Late Ordovician) Brachiopod Species of the Cincinnati Arch: a Test of Niche Modeling Methods for Paleobiogeographic Reconstruction." Ohio : Ohio University, 2009. http://www.ohiolink.edu/etd/view.cgi?ohiou1243010764.

Full text

APA, Harvard, Vancouver, ISO, and other styles

19

Serra, Díaz Josep M. "Applying correlative ecological niche models to global change studies." Doctoral thesis, Universitat Autònoma de Barcelona, 2012. http://hdl.handle.net/10803/96302.

Full text

Abstract:

La distribució de les espècies ha estat objecte d’estudi per part de diverses disciplines donada la seva naturalesa multifactorial. Així, entendre veritablement la distribució de les espècies implica necessàriament un millor coneixement del funcionament de la biosfera. D’altra banda, el canvi global que està patint el nostre planeta previsiblement afectarà en gran mesura moltes espècies, variant així la distribució i composició dels ecosistemes tal i com els coneixem avui dia i implícitament dels serveis que proporcionen. La modelització ha permès augmentar el nostre grau de comprensió sobre el sistema Terra així com de les potencials conseqüències que els canvis antropogènics poden provocar (canvi climàtic, alteració de cicles biogeoquímics, destrucció d’hàbitats, etc.). En el camp de la distribució d’espècies, els models de nínxol ecològic han estat àmpliament utilitzats per estudiar i preveure canvis en la distribució dels organismes. Aquests models es basen en la determinació de les condicions ambientals òptimes on una determinada espècie pot viure i reproduir-se (nínxol). Tanmateix, aquests models fan ús d’aproximacions correlatives entre presències i variables ambientals actuals, fet que presenta diverses desavantatges que posen de manifest una gran incertesa en les prediccions i fins i tot, qüestionen la seva utilitat en el context de canvi global. El conjunt dels treballs que s’exposen pretenen donar una visió sintètica de la possibilitat d’ús d’aquests models per a prediccions de distribució d’espècies vegetals, tant presents com futures. La present recerca se centra en l’anàlisi de diversos aspectes problemàtics per a aquests models en la predicció de la distribució´ d’espècies vegetals en el context del canvi global. Específicament s’ha avaluat la diferència entre prediccions basades en models ecofisiològics i models correlatius sobre l’efecte de prediccions actuals i futures , la variació entre prediccions a nivell de taxó o a nivell de comunitat, la variació en la predicció de canvi de nínxol davant possibles invasions i finalment, l’addició de l’escala temporal en les prediccions. S’ha pogut constatar que el fet de basar-se en correlacions estàtiques minva la seva capacitat de transferència a noves situacions i no incorpora trets biològics que poden tenir una importància cabdal (p.ex. fisiologia). En situacions de projeccions en l’espai i en el temps, s’observen importants variacions espacials en les prediccions, tant a nivell de comunitat com a nivell de poblacions de diversa provinença. Això comporta que les assumpcions i l’escala geogràfica i biològica hagin de ser adaptades segons la qüestió a la que el model s’adreça així com de la disponibilitat de dades. A més, incorporar l’escala temporal pot afegir una cert grau de dinamisme a aquests models estàtics, malgrat que no es poden inferir efectes a una resolució temporal adequada per a alguns fenòmens climàtics extrems . Dels resultats se’n desprèn que la utilització d’aquests models pot servir com a una bona eina de generació d’hipòtesis sobre dels diferents factors que actualment constrenyen la distribució de les espècies. A més, pot ser una tècnica potent per estimar el grau d’exposició de les espècies davant noves situacions de canvi global. Tot i això, les seves prediccions han de ser confrontades amb d’altres tècniques oimés quan es tracta de valorar escenaris plausibles subjectes a una gran incertesa. En general, aquests models són molt significatius per a la caracterització de l’exposició a noves situacions.
La distribución de las especies ha sido objetos de estudio por parte de diversas disciplinas dada su naturaleza multifactorial. Así, entender verdaderamente la distribución de las especies implica necesariamente un mejor conocimiento del funcionamiento de la biosfera. Por otro lado, el cambio global que esta sufriendo nuestro planeta previsiblemente afectará en gran medida muchas especies, variando su distribución y en última instancia, la composición de los ecosistemas tal y como los conocemos hoy día así como los servicios que proporcionan. La modelización ha permitido aumentar nuestro grado de comprensión sobre el sistema Tierra así como de las potenciales consecuencias que los cambios antropogénicos pueden provocar (cambio climático, alteración de ciclos biogeoquímicos, destrucción de hábitats, etc.). En el campo de la distribución de especies, los modelos de nicho ecológico han sido ampliamente utilizados para estudiar y predecir cambios en la distribución de los organismos. Estos modelos se basan en la determinación de las condiciones ambientales óptimas en las que una determinada especie puede vivir y reproducirse (nicho). Sin embargo, estos modelos utilizan una aproximación correlativa entre presencia de un organismo y las variables ambientales actuales, hecho que presenta diversas desventajas que ponen de manifiesto una gran incertidumbre en las predicciones e incluso, cuestionan su utilidad en el contexto del cambio global. El conjunto de los trabajos que aquí se exponen pretenden dar una visión sintética de la posibilidad de uso de estos modelos para predicciones de la distribución de especies vegetales, tanto presentes como futuras. La presente investigación se centra en el análisis de aspectos problemáticos de índole diversa de este tipo de modelos, cuando son aplicados para predecir la distribución de especies vegetales bajo supuestos de cambio global. Específicamente se ha evaluado la diferencia entre predicciones basadas en modelos ecofisiológicos y modelos correlativos en la predicción de distribuciones presentes y futuras, la variación entre predicciones a nivel de taxón o a niveles de comunidad, la variación en la predicción según la población bajo riesgos potenciales de cambio de nicho i finalmente, la adición de la escala temporal en las predicciones. Se ha podido constatar que el hecho de basarse en correlaciones estáticas disminuye su capacidad de transferencia a nuevas situaciones i no incorpora características biológicas que pueden tener una importancia vital (p.ej. fisiología). En situaciones de proyecciones en el espacio y el tiempo, se observan variaciones espaciales significativas en las predicciones, tanto a nivel de comunidad como a nivel de poblaciones de diverso origen. Esto comporta que las asunción i la correcta elección de la escala geográfica i biológica según el objetivo del modelo. Además, la incorporación de la escala temporal puede añadir un cierto grado de dinamismo a estos modelos estáticos, a pesar que no se pueden inferir efectos a una resolución temporal adecuada para algunos fenómenos climáticos extremos. En general, dichos modelos son relevantes para caracterizar la exposición a nuevas situaciones.
The distribution of species has been studied by various disciplines due to its multifactorial nature. Thus, to truly understand the distribution of species necessarily implies a better understanding of the functioning of the biosphere. On the other hand, the overall change our planet is undergoing, it is expected to greatly affect many species, varying distribution and ultimately the composition of ecosystems as we know them today and the services they provide. The modeling has enhanced our level of understanding of the Earth system and the potential consequences that anthropogenic changes can cause (climate change, alteration of biogeochemical cycles, habitat destruction, etc..). In the field of species distribution, ecological niche models have been widely used to study and predict changes in the distribution of organisms. These models are based on determining the optimum environmental conditions in which a species can live and reproduce (niche). However, these models use a correlative approach between the presence of an organism and the current environmental variables, which has several disadvantages that cause a uncertainty in predictions and even question their usefulness in the context of global change. All the works presented here are intended to give a synthetic view of the possibility of using these models for predictions of the distribution of plant species, both present and future. This research focuses on the analysis of problematic aspects of these models, when applied to predict the distribution of plant species under global change scenarios. Specifically we evaluated the difference between model predictions and ecophysiological models to predict correlative and future distributions, the variation between predictions at the level of taxon or community levels, the variation in the prediction at the population levels and finally, the addition of the timescale in the predictions. It has been shown that basing predictions on static correlations diminishes their transference capacity to new situations and does not incorporate key biological traits that may play a key role (e.g. physiology). In projections in space and time, it has been observed significant spatial variations in predictions, whether at the community or individual level of species or different populations across continents. This implies that the choice of the biological or geographical scale may be fit for model’s purpose. Furthermore, the incorporation of the temporal scale may add a certain degree of dynamism to these static modles, despite they cannot be infered for effects at higher temporal resolution for some extreme climatic events. In general, such models are relevant to characterize exposure to new situations.

APA, Harvard, Vancouver, ISO, and other styles

20

Favalesso, Marília Melo. "Condições ecológicas e predição de áreas adequáveis para ocorrência de Lonomia obliqua Walker 1855 no Brasil." Universidade Estadual do Oeste do Paraná, 2018. http://tede.unioeste.br/handle/tede/3961.

Full text

Abstract:

Submitted by Edineia Teixeira (edineia.teixeira@unioeste.br) on 2018-09-28T18:12:13Z No. of bitstreams: 2 Marilia_Favalesso_2018.pdf: 1901703 bytes, checksum: 0d9b6ae60903ec7aa858792cf86a51f2 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5)
Made available in DSpace on 2018-09-28T18:12:13Z (GMT). No. of bitstreams: 2 Marilia_Favalesso_2018.pdf: 1901703 bytes, checksum: 0d9b6ae60903ec7aa858792cf86a51f2 (MD5) license_rdf: 0 bytes, checksum: d41d8cd98f00b204e9800998ecf8427e (MD5) Previous issue date: 2018-02-19
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior - CAPES
Lonomia obliqua Walker 1855 (Saturniidae: Hemileucinae) is a species of moth of sanitary interest in Brazil. Their larvae are etiological agents of lonomism, a form of erucism caused by the contact of the human beings with the stinging structures of the species. The most worrying symptoms of lonomism are the systemic hemorrhagic conditions that can lead to several outcomes, including death. The first official notifications of accidents with the species date back to the end of the 80s, in the state of Rio Grande do Sul. Since then, several accidents have been documented in Brazil, mainly in the south and southeast regions of the country. With the increase in the number of victims, health authorities in the state of São Paulo, represented by the “Instituto Butantã”, developed an anti-lonomic serum, which is distributed by the Ministry of Health in places with a higher prevalence of accidents. Hypotheses have been raised on the relation between the growth of the cases of lonomismo and the human occupation; however, little is known about the spatial distribution and ecological aspects of the species to enable the testing of these hypotheses. In view of the above, the present study aimed to produce a map for the potential geographical distribution of L. obliqua in Brazil, based on the combination of different ENM (Ecological Niche Modeling) algorithms. A total of 38 occurrence points were distributed across the geographic area of Brazil and Misiones, Argentina, which were partitioned for calibration and evaluation of the distribution model. Eight continuous climatic variables and only 16 previously considered variables were selected. Different ENM methodologies were tested and compared to TSS (True Skill Statistic) index values. The final model-map was composed of a combination of four algorithms (Gower, Mahalanobis, Maxent and SVM), with pseudo-absences outside a bioclimatic envelope and a number of pseudo-absences equal to that of presences. This model map was binarized from the Low Presence Threshold (LPT) and cut only for Brazil. According to this model map, the areas predicted as suitable for L. obliqua would be restricted to latitudes ~12° and ~32°, and longitudes ~39° and ~57°. When evaluating new sites of occurrence of the specie in Rio Grande do Sul, it was possible to verify that all the municipalities were in areas predicted by the model-map. A characterization of the abiotic variables related to the niche of the specie was also carried out, being these extracted from the area predicted as adequate the presence of the specie in the model map. To help characterize these variables, we also extract categorical descriptors of climate, soil and vegetation (in %). The percentage of land use classes was also extracted in order to contribute to the hypothesis that condition the increase of accidents due to human occupation. In this question, we find a large part of the area predicted within classes of agricultural soils in Brazil, which leads us to ratify the current hypotheses. Thus, the loss of habitat of the species for the agricultural enterprises increases the human contact with the specie, which should increase the number of notifications of the lonomism, generating greater epidemiological concern and habitat conservation for this specie.
Lonomia obliqua Walker 1855 (Saturniidae: Hemileucinae) é uma espécie de mariposa de interesse sanitário no Brasil. Suas larvas são agentes etiológicos do lonomismo, uma forma de erucismo causado pelo contato dos seres humanos com as estruturas urticantes da espécie. Os sintomas mais preocupantes do lonomismo são os quadros hemorrágicos sistêmicos que podem conduzir a diversos desfechos, inclusive o óbito. As primeiras notificações oficiais de acidentes com a espécie datam do final da década de 80, no estado do Rio Grande do Sul. A partir de então, diversos acidentes têm sido documentados no Brasil, principalmente nas regiões sul e sudeste do país. Com o aumento do número de vítimas, autoridades sanitárias do estado de São Paulo, representadas pelo do Instituto Butantã, desenvolveram um soro antilonômico, o qual é distribuído pelo Ministério da Saúde em localidades com maior prevalência de acidentes. Hipóteses têm sido levantadas sobre a relação entre o crescimento dos casos de lonomismo e a ocupação humana; contudo, pouco se conhece sobre a distribuição espacial e aspectos ecológicos da espécie para possibilitar os testes destas hipóteses. Diante do exposto, o presente estudo objetivou produzir um mapa para a distribuição geográfica potencial de L. obliqua no Brasil, baseando-se na combinação de diferentes algoritmos ENM (Ecological Niche Modeling). Foram utilizados 38 pontos de ocorrência distribuídos pela área geográfica do Brasil e região de Misiones, na Argentina, os quais foram particionados para calibração e avaliação do modelo de distribuição. Foram selecionadas oito variáveis contínuas climáticas e de solo entre 16 previamente cogitadas. Diferentes metodologias ENM foram testadas e confrontados quanto a valores de índice TSS (True Skill Statistic). O mapa-modelo final foi composto por uma combinação de quatro algoritmos (Gower, Mahalanobis, Maxent e SVM), com amostragens de pseudo-ausências fora de um envelope bioclimático e número de pseudo-ausências igual ao de presenças. Esse mapa-modelo foi binarizado a partir do limiar LPT (Lowest Presence Threshold) e recortado somente para o Brasil. Segundo este mapa-modelo, as áreas preditas como adequáveis a L. obliqua estariam restritas as latitudes ~12º e ~32º, e as longitudes ~39º e ~57º. Também foi realizada uma caracterização das variáveis abióticas relacionadas ao nicho da espécie, sendo essas extraídas da área predita como adequada a presença da espécie no mapa-modelo. O percentual de classes de uso da terra também foi extraído, a fim de contribuir com as hipóteses que condicionam o aumento de acidentes em função da ocupação humana. Neste quesito, encontramos grande parte da área predita dentro de classes de solos agrícolas no Brasil, o que nos leva a ratificar as hipóteses atuais. Assim, a perda de habitat da espécie para os empreendimentos agrícolas aumenta o contato humano com a espécie, o que deve aumentar o número de notificações do lonomismo, gerando maior preocupação a nível epidemiológico e de conservação de habitat para essa espécie.

APA, Harvard, Vancouver, ISO, and other styles

21

Schmieder, Daniela Anna [Verfasser]. "Niche partitioning in similar, closely related sympatric bat species? : A mechanical approach. / Daniela Anna Schmieder." Konstanz : Bibliothek der Universität Konstanz, 2017. http://d-nb.info/1137161507/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

22

Sch?bel, Christian. "Niche Modeling of the economical important Mahanarva species in South and Central America (HEMIPTERA, CERCOPIDAE)." Pontif?cia Universidade Cat?lica do Rio Grande do Sul, 2018. http://tede2.pucrs.br/tede2/handle/tede/8004.

Full text

Abstract:

Submitted by PPG Zoologia (zoologia-pg@pucrs.br) on 2018-04-20T12:08:51Z No. of bitstreams: 1 Disserta??o corre??o final - Christian.pdf: 2735367 bytes, checksum: 73fdc67c9898d886fdbd0e0cce1dfad3 (MD5)
Approved for entry into archive by Caroline Xavier (caroline.xavier@pucrs.br) on 2018-05-08T16:47:52Z (GMT) No. of bitstreams: 1 Disserta??o corre??o final - Christian.pdf: 2735367 bytes, checksum: 73fdc67c9898d886fdbd0e0cce1dfad3 (MD5)
Made available in DSpace on 2018-05-08T16:53:43Z (GMT). No. of bitstreams: 1 Disserta??o corre??o final - Christian.pdf: 2735367 bytes, checksum: 73fdc67c9898d886fdbd0e0cce1dfad3 (MD5) Previous issue date: 2018-02-22
Conselho Nacional de Pesquisa e Desenvolvimento Cient?fico e Tecnol?gico - CNPq
Mahanarva fimbriolata, M. spectabilis, M. liturata and M. posticata (Hemiptera: Cercopidae) s?o conhecidas como pragas de planta??es de cana-de-a??car e pastagem em todo Brasil. Por alimentarem-se diretamente da seiva das plantas, esses cercop?deos causam fitotoxicidade e devido a isso diminuem a produ??o. A modelagem da distribui??o de esp?cies permite analisar a poss?vel occurencia das quatro esp?cies na Am?rica do Sul e Central. Para criar modelos de distribui??o de esp?cies foram utilizados em R, os algoritmos Bioclim, Domain, diferentes modelos lineares generalizados e Maxent. Nesses modelos foram utilizadas vari?veis bioclim?ticas atuais e futuras, al?m da eleva??o e outras vari?veis agr?colas. As vari?veis clim?ticas futuras s?o para os anos 2050 e 2070 com diferentes repentant concentration pathways. As esp?cies apresentam habitats adequados em diferentes pa?ses da Am?rica do Sul e Central, onde as planta??es de cana-de-a??car s?o abundantes. Os resultados das an?lises clim?ticas futuras n?o apresentaram diferen?as em rela??o ?s an?lises clim?ticas atuais. No geral, o algoritmo Maxent mostrou os maiores valores de AUC e o Bioclim os menores. As vari?veis que mais contribu?ram para os modelos s?o: eleva??o, isothermality e diferentes vari?veis de precipita??o. As mudan?as clim?ticas e ciclos de vida de insetos adicionais n?o t?m impacto em habitats adequados dos insetos. Em geral, o Maxent ? o melhor algoritmo para realizar modelos de distribui??o de esp?cies com um n?mero baixo de pontos de ocorr?ncia e an?lises de mudan?as clim?ticas.
Mahanarva fimbriolata, M. spectabilis, M. liturata and M. posticata (Hemiptera: Cercopidae) are known pests for sugarcane and pasture plantations throughout Brazil. By direct sap feeding on the plants they cause phytotoxicity and due to this they decrease the production of plantations. With species distribution modeling it is possible to analyze the possible occurence of the four species in South and Central America. To create species distribution models the algorithms Bioclim, Domain, different generalized linear models and Maxent were used in R. For those models current and future bioclimatic variables as well as elevation and other agricultural variables were used. The future climatic variables are for the years 2050 and 2070 with different repentant concentration pathways. The species show suitable habitats in different countries in South and Central America where sugarcane plantations are abundant. The results of the future climate analyzes do not show differences compared to the current climate analyzes. Overall the Maxent algorithm showed the highest AUC scores and Bioclim the lowest. The variables which contributed the most to the models are elevation, isothermality and different precipitation variables. Climate change and therefore additional insect lifecycles do not have an impact on the insect?s suitable habitats. Overall Maxent is the best algorithm to perform species distribution models with a low number of occurrence points and for climate change analyzes.

APA, Harvard, Vancouver, ISO, and other styles

23

Farallo, Vincent R. "Notes from the Underground: Linking Microhabitat and Species Distributions of Plethodontid Salamanders." Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou148156741016879.

Full text

APA, Harvard, Vancouver, ISO, and other styles

24

Brabazon, Holly Kathryn. "Delimiting Species and Varieties of Cycladenia humilis (Apocynaceae)." BYU ScholarsArchive, 2015. https://scholarsarchive.byu.edu/etd/5921.

Full text

Abstract:

Taxonomic delimitation of rare species is vital for accurate assessments of diversity and for their conservation. Cycladenia humilis, the sole species of Cycladenia, is an enigmatic perennial widely dispersed across the western United States. Within this species there are three currently recognized varieties: C. humilis var. humilis in Northern California, C. humilis var. venusta in Southern California, and C. humilis var. jonesii in Utah and Northern Arizona. Some populations occur geographically in areas between the typical distribution of each variety and the presently accepted taxonomy inadequately addresses these populations. Using five nDNA regions, we seek to clarify relationships between current varieties and assess the pattern of variation throughout the species. Analyses including K-means clustering, principle component analysis, fields for recombination, AMOVA, and ecological niche modeling were applied. Results indicate significant genetic structure between varieties and supports recognition of C. jonesii at the species level as distinct from C. humilis. Well defined intraspecific groupings are evident in the data, with evidence supporting the recognition of an additional variety in C. humilis, and two varieties in C. jonesii. Haplotype diversity and relationships between metapopulation clusters inform conservation efforts regarding diversity within Cycladenia and offer insights into the historical demography of this genus.

APA, Harvard, Vancouver, ISO, and other styles

25

Priddis, Edmund R. "Niche Separation Along Environmental Gradients as a Mechanism to Promote the Coexistence of Native and Invasive Species." Diss., CLICK HERE for online access, 2007. http://contentdm.lib.byu.edu/ETD/image/etd2199.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

26

LIMA, JUNIOR Dilermando Pereira. "Transformando tropeços em passos de dança: o uso de espécies exóticas para estudos biogeográficos." Universidade Federal de Goiás, 2008. http://repositorio.bc.ufg.br/tede/handle/tde/2548.

Full text

Abstract:

Made available in DSpace on 2014-07-29T16:21:15Z (GMT). No. of bitstreams: 1 Dissertacao Dilermando P L Jr.pdf: 360879 bytes, checksum: 1c2f22ea2b7828ee7c6779ffd933fed4 (MD5) Previous issue date: 2008-02-27
The establishment of exotic species is known for the negative impacts it causes. However, it can be used as models to study the ecological and evolutionary causes of biogeography patterns and access whether the niche conservatism is the determinant of the species limits distribution. The main purpose of this study is to evaluate the difference between pools of exotic fish species in biogeographical regions of the world based on the theories of Niche Conservatism and Evolutionary Dynamics of Latitudinal Gradients of Diversity. We found a strong tendency of the niche conservatism with exotic fishes, but no phylogentic structures of the invaders fishes were found. Therefore, predictive models that purpose to evaluate the potential invasion of fishes has to, include extrinsic factors as climatic conditions, propagule pressure, environmental disturbance, human use and intrinsic factors as parental care and body size of the species.
Os estabelecimentos de espécies exóticas são muito conhecidos por seus impactos, contudo podem servir como modelo de estudo das causas ecológicas e evolutivas dos padrões biogeográficos e avaliar se a conservação de nicho é determinante dos limites de distribuições das espécies. Este estudo tem por objetivo avaliar a diferença entre o conjunto de espécies exóticas de peixes nas diferentes regiões biogeográficas do planeta tendo como base as teorias de conservação filogenética e da dinâmica evolutiva de gradientes latitudinais de diversidade. Encontramos uma forte tendência de conservação de nicho, mas nenhum sinal de estruturação filogenética da invasão. Portanto, modelos preditivos que possuem o intuito de avaliar o potencial invasor de peixes têm, necessariamente, têm que incluir fatores extrínsecos às espécies e à condição climática da região nativa, pressão de propágulos, distúrbios no ambiente, uso humano e fatores intrínsecos como cuidado parental e tamanho corporal das espécies.

APA, Harvard, Vancouver, ISO, and other styles

27

Brum, Mauro 1984. "Partição de recursos hídricos em comunidades vegetais de campo rupestre e campo de altitude no Sudeste brasileiro." [s.n.], 2013. http://repositorio.unicamp.br/jspui/handle/REPOSIP/316211.

Full text

Abstract:

Orientador: Rafael Silva Oliveira
Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia.
Made available in DSpace on 2018-08-22T05:52:27Z (GMT). No. of bitstreams: 1 BrumJr._Mauro_M.pdf: 3526243 bytes, checksum: 44324833dc08e57ffd87e138721c4c83 (MD5) Previous issue date: 2013
Resumo: A partição de recursos hídricos do solo é um dos modelos plausíveis para explicar os mecanismos que promovem a coexistência e a diferenciação de nicho entre espécies em comunidades vegetais. As raízes constituem a principal interface de troca de água entre a planta e o solo, de modo que profundidade radicular é um atributo chave que pode influenciar o funcionamento hidráulico das plantas. O campo rupestre e o campo de altitude são vegetações campestres que ocorrem em montanhas ou chapadas sob diferentes regimes de água devido às diferenças climáticas e pedológicas, sendo o campo rupestre mais árido que o campo de altitude. Essas comunidades são bem conhecidas devido à alta diversidade de espécies, mas pouco se sabe a respeito da diversidade de estratégias de uso de água. Entender as estratégias hidráulicas das plantas é importante para fazer previsões das respostas das comunidades em relação às mudanças climáticas. Diante disso, o nosso objetivo foi responder: quais são os padrões de aquisição e uso de água por plantas que coexistem em uma vegetação de campo rupestre e outra de campo de altitude? Além disso, quais são as estratégias de uso de água entre as plantas com sistemas subterrâneos contrastantes nessas comunidades? Nós avaliamos a composição de isótopos estáveis da água do solo e contrastamos com a composição isotópica da água do xilema de 15 espécies de plantas em cada comunidade. A composição isotópica da água do xilema foi usada como um indicador para estimar a profundidade do solo na qual as plantas estão absorvendo a água. Também fizemos escavações das raízes para verificar qual é o tipo morfológico de cada espécie e contrastar com os resultados da composição isotópica da água do xilema. Além disso, medimos o potencial hídrico da madrugada, do meio dia e a condutância estomática máxima três vezes durante a estação seca (junho, julho e agosto). Nós demonstramos que em ambas as comunidades há uma diversidade interespecífica de formas de sistemas subterrâneos, sendo que o campo rupestre apresentou maior variação interespecífica de uso de água em perfis verticais do solo. As plantas do campo de altitude apresentam raízes mais superficiais do que no campo rupestre. Além disso, demonstramos que a profundidade do sistema radicular é um bom preditor do potencial hídrico da madrugada e do grau de regulação estomática para as plantas do campo rupestre, mas não do campo de altitude. Não encontramos relação entre a profundidade do sistema radicular e o potencial hídrico do meio dia em ambas as comunidades
Abstract: Soil water partitioning is a plausible model to explain the mechanisms that allow species coexistence and niche segregation in plant communities. Roots are the main interface of water exchange between plant and soil, so rooting depth is a key trait that affects whole-plant hydraulic function. The campos rupestres and campos de altitude are two shrubland communities that occur in mountainous plateaus under contrasting water regimes due to differences in their climatic and pedological variables, campos rupestres being more arid than campos de altitude. These communities are well known for their high species diversity but little is known about the diversity of water use strategies. Understanding plant hydraulic strategies is important for improving predictions of community responses to changes in climate. Our goal was to respond: what are the patterns of water acquisition and use in campo rupestres and campo de altitude? Furthermore, what are the water use strategies of plants with contrasting rooting depths in these plants communities? We evaluated the ?D of soil water and xylem water of 15 species in each community. The ?D of xylem water was used as proxy of rooting depth. We also excavated the roots of all species to evaluate their root morphological pattern and to compare with the isotopic data. Furthermore, we measured pre-dawn and midday water potentials and stomatal conductance three times during the dry season (June, July and August, 2012). We found a high interespecific diversity of root types in both communities and higher variance of hydraulic traits at campo rupestre. Campo de altitude plants had shallower roots than campo rupestre. Moreover, we demonstrated that pre-dawn water potential is a good predictor of rooting depth, which in turn is a good predictor of the degree of stomatal control for campo rupestre community but these patterns were not found at campo de altitude. We did not find any relationship between rooting depth and midday water potential for both communities
Mestrado
Ecologia
Mestre em Ecologia

APA, Harvard, Vancouver, ISO, and other styles

28

Nyström, Sandman Antonia. "Modelling spatial and temporal species distribution in the Baltic Sea phytobenthic zone." Doctoral thesis, Stockholms universitet, Systemekologiska institutionen, 2011. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-54269.

Full text

Abstract:

Statistical modelling is often used to relate the presence or abundance of species to environmental predictors, thereby providing a basis for predictive mapping of species or biodiversity. The variables included must thus be relevant and reflect actual changes in the environment. Therefore, the quantification of species–environment relationships is an important aspect of predictive modelling. This thesis examines how phytobenthic species or communities in the Baltic Sea relate to environmental gradients, and if different aspects of phytobenthic species distribution in the Baltic Sea could be explained by spatial or temporal variation in environmental factors. Predictive distribution modelling usually focuses on how environmental variables control the distribution of species or communities. Thus the relative weight of the predictor variables on different scales is of importance. In this thesis, I show that the relative importance of environmental variables depends both on geographic scale and location, and that it also differs between species or species groups. There are no simple explanations to the temporal variability in species occurrence. I here show that the temporal changes in species distribution within the phytobentic zone varies in a spatial context. I also try to find temporal and spatio-temporal patterns in species distribution that could be related to changes in climate or anthropogenic disturbance. However, the findings in this thesis suggest that single factor explanations are insufficient for explaining large-scale changes in species distribution. A greater understanding of the relationship between species and their environment will lead to the development of more sensitive models of species distributions. The predictions can be used to visualise spatial changes in the distribution of plant and animal communities over time.
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Submitted. Paper 3: Manuscript. Paper 4: Manuscript. Paper 5: Manuscript.

APA, Harvard, Vancouver, ISO, and other styles

29

Schmitt, Sylvain. "Ecological genomics of niche exploitation and individual performance in tropical forest trees." Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0247.

Full text

Abstract:

Les forêts tropicales abritent la plus grande diversité d'espèces au monde, un fait qui reste en partie inexpliqué et dont l'origine est sujette à débat. Même à l'échelle de l'hectare, les forêts tropicales abritent des genres riches en espèces, avec des espèces d’arbres étroitement apparentées qui coexistent en sympatrie. En raison de contraintes phylogénétiques, on s'attend à ce que les espèces étroitement apparentées possèdent des niches et des stratégies fonctionnelles similaires, ce qui questionne les mécanismes de leur coexistence locale. Les espèces étroitement apparentées peuvent former un complexe d'espèces, composé d’espèces morphologiquement similaires ou qui partagent une importante proportion de leur variabilité génétique en raison d'une ascendance commune récente ou d'hybridation, et qui peut résulter d'une radiation écologique adaptative des espèces selon des gradients environnementaux. Malgré le rôle clé des complexes d'espèces dans l'écologie, la diversification et l'évolution des forêts néotropicales, les forces éco-évolutives qui créent et maintiennent la diversité au sein des complexes d'espèces néotropicales restent peu connues. Nous avons exploré la variabilité génétique intraspécifique comme un continuum au sein de populations structurées d'espèces étroitement apparentées, et mesuré son rôle sur la performance individuelle des arbres à travers la croissance dans le temps, tout en tenant compte des effets d'un environnement finement caractérisé au niveau abiotique et biotique. En combinant des inventaires forestiers, des données topographiques, des traits fonctionnels foliaires et des données de capture de gènes dans la station de recherche de Paracou, en Guyane Française, nous avons utilisé la génomique des populations, les analyses d'associations environnementales et génomiques, et la modélisation Bayésienne sur les complexes d'espèces Symphonia et Eschweilera clade Parvifolia. Nous avons montré que les complexes d'espèces d'arbres couvrent l’ensemble des gradients locaux de topographie et de compétition présents dans le site d'étude alors que la plupart des espèces qui les composent présentent une différenciation de niche marquée le long de ces mêmes gradients. Plus précisément, dans les complexes d'espèces étudiés, la diminution de la disponibilité en eau, par exemple depuis les bas-fonds jusqu’aux plateaux, a entraîné une modification des traits fonctionnels foliaires, depuis des stratégies d'acquisition à des stratégies conservatrices, tant entre les espèces qu'au sein de celles-ci. Les espèces de Symphonia sont génétiquement adaptées à la distribution de l'eau et des nutriments, elles coexistent donc localement en exploitant un large gradient d'habitats locaux. Inversement, les espèces d'Eschweilera sont différentiellement adaptées à la chimie du sol et évitent les habitats les plus humides et hydromorphes. Enfin, les génotypes individuels des espèces de Symphonia sont différentiellement adaptés pour se régénérer et croître en réponse à la fine dynamique spatio-temporelle des trouées forestières, avec des stratégies adaptatives de croissance divergentes le long des niches de succession. Par conséquent, la topographie et la dynamique des trouées forestières entraînent des adaptations spatio-temporelles à fine échelle des individus au sein et entre les espèces des complexes d'espèces Symphonia et Eschweilera. Je suggère que les adaptations à la topographie et à la dynamique des trouées forestières favorisent la coexistence des individus au sein et entre les espèces des complexes d'espèces, et peut-être plus généralement entre les espèces d'arbres de forêts matures. Dans l'ensemble, je soutiens le rôle primordial des individus au sein des espèces dans la diversité des forêts tropicales, et suggère que nous devrions élaborer une théorie de l'écologie des communautés en commençant par les individus, car les interactions avec les environnements se produisent après tout au niveau de l’individu
Tropical forests shelter the highest species diversity worldwide, a fact that remains partly unexplained and the origin of which is subject to debate. Even at the hectare-scale, tropical forests shelter species-rich genera with closely-related tree species coexisting in sympatry. Due to phylogenetic constraints, closely related species are expected to have similar niches and functional strategies, which raises questions on the mechanisms of their local coexistence. Closely related species may form a species complex, defined as morphologically similar species that share large amounts of genetic variation due to recent common ancestry and hybridization, and that can result from ecological adaptive radiation of species segregating along environmental gradients. Despite the key role of species complexes in Neotropical forest ecology, diversification, and evolution, little is known of the eco-evolutionary forces creating and maintaining diversity within Neotropical species complexes. We explored the intraspecific genomic variability as a continuum within structured populations of closely related species, and measured its role on individual tree performance through growth over time, while accounting for effects of a finely-characterized environment at the abiotic and biotic level. Combining tree inventories, LiDAR-derived topographic data, leaf functional traits, and gene capture data in the research station of Paracou, French Guiana, we used population genomics, environmental association analyses, genome-wide association studies and Bayesian modelling on the tree species complexes Symphonia and Eschweilera clade Parvifolia. We showed that the species complexes of Neotropical trees cover all local gradients of topography and competition and are therefore widespread in the study site whereas most of the species within them exhibit pervasive niche differentiation along these same gradients. Specifically, in the species complexes Symphonia and Eschweilera clade Parvifolia, the decrease in water availability due to higher topographic position, e.g., from bottomlands to plateaus, has led to a change in leaf functional traits from acquisitive strategies to conservative strategies, both among and within species. Symphonia species are genetically adapted to the distribution of water and nutrients, hence they coexist locally through exploiting a broad gradient of local habitats. Conversely, Eschweilera species are differentially adapted to soil chemistry and avoid the wettest, hydromorphic habitats. Last but not least, individual tree genotypes of Symphonia species are differentially adapted to regenerate and thrive in response to the fine spatio-temporal dynamics of forest gaps with divergent adaptive growth strategies along successional niches. Consequently, topography and the dynamics of forest gaps drive fine-scale spatio-temporal adaptations of individuals within and among distinct but genetically connected species within the species complexes Symphonia and Eschweilera clade Parvifolia. Fine-scale topography drives genetic divergence and niche differentiation with genetic adaptations among species, while forest gap dynamics maintains genetic diversity with divergent adaptive strategies within species. I suggest that adaptations of tree species and individuals to topography and dynamics of forest gaps promote coexistence within and among species within species complexes, and perhaps among mature forest tree species outside species complexes. Overall, I defend the primordial role of individuals within species in tropical forest diversity, suggesting that we should develop a theory of community ecology starting with individuals, because interactions with environments happen after all at the individual level

APA, Harvard, Vancouver, ISO, and other styles

30

Yadav, Sunita. "The Influence of Climate and Topography in Modeling Distributions for Species with Restricted Ranges: A Case Study Using the Hawaiian Endemic Plant Genus, Schiedea (Caryophyllaceae)." University of Cincinnati / OhioLINK, 2015. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1447690823.

Full text

APA, Harvard, Vancouver, ISO, and other styles

31

Wenzel, Aaron. "Systematics of Penstemon section Ericopsis, a group of plant species native to the Intermountain West." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1471533204.

Full text

APA, Harvard, Vancouver, ISO, and other styles

32

Lakoba, Vasiliy Tarasovich. "Ecotypic Variation in Johnsongrass in Its Invaded U.S. Range." Diss., Virginia Tech, 2021. http://hdl.handle.net/10919/103611.

Full text

Abstract:

Biological invasions have been observed throughout the world for centuries, often with major consequences to biodiversity and food security. Tying invasion to species identity and associated traits has led to numerous hypotheses on why, and where, some species are invasive. In recent decades, attention to intraspecific variation among invaders has produced questions about their adaptation to climate, land use, and environmental change. I examined the intraspecific variation of invasive Johnsongrass's (Sorghum halepense (L.) Pers.) seedling stress response, propagule cold tolerance, and large-scale niche dynamics for correlation with populations' climatic and ecotypic (i.e., agricultural vs. non-agricultural) origin. Overall, I found a greater number of home climate effects than ecotypic effects on various traits. Non-agricultural seed from cold climates and agricultural seed from warm climates germinated more and faster, while non-agricultural seedlings showed uniform chlorophyll production regardless of home soil carbon origin, unlike their agricultural counterparts. Neither seedling stress response nor propagule cold tolerance interacted with ecotype identity; however, drought stress varied with population origins' aridity and soil fertility, and seed from warm/humid and cold/dry climates was most germinable. Comparison of seed and rhizome cold tolerance also suggested that the latter is a conserved trait that may be limiting S. halepense poleward range expansion. This physiological limit, an unchanged cold temperature niche boundary between continents and ecotypes, and a narrowed niche following transition to non-agricultural lands all imply low likelihood of spread based on climatic niche shift. Instead, evidence points to range expansion driven primarily by climate change and highlights agriculture's role in facilitating invasibility. This tandem approach to climate and land use as drivers of intraspecific variation is transferable to other taxa and can help refine our conception of and response to invasion in the Anthropocene.
Doctor of Philosophy
Exotic invasive species are a global problem, threatening biodiversity and biosecurity now and in the future. In the last several decades, ecologists have studied many individual invaders and their traits to understand what drives their spread. More recently, abundant differences in traits between populations within an invasive species have raised questions about humans' role in facilitating invasion through climate change, land use, and other disturbances. I studied the invasive Johnsongrass's (Sorghum halepense (L.) Pers.) response to drought, nutrient limitation, and freezing to detect differences between populations based on their climate and ecotype (agricultural vs. non-agricultural) origin. I also tracked differences in the climates the species occupied across the globe and North America and projected its future distribution under climate change. Overall, I found a greater number of home climate effects than ecotypic effects on various traits. Non-agricultural seed from cold climates and agricultural seed from warm climates germinated the most, while non-agricultural seedlings performed consistently regardless of soil carbon origin, unlike their agricultural counterparts. In addition, drought stress varied with population origins' rainfall and soil fertility, and seed germination favored warm/humid and cold/dry origin. Rhizome (underground stem) cold tolerance appears to be a trait that limits S. halepense poleward range expansion. Along with no change in the coldest climates occupied worldwide and no spread to new climates with transition to non-agricultural lands, this implies that Johnsongrass is unlikely to expand its range without external forces. Instead future range expansion will likely be driven by climate change. This coupled approach to climate and land use affecting invasion is transferable to other species and can help refine both our concepts and response strategies.

APA, Harvard, Vancouver, ISO, and other styles

33

Escoriza, Daniel. "Factors regulating the invasion of two Mediterranean anurans. The role of niche conservatism, species interaction and habitat selection." Doctoral thesis, Universitat de Girona, 2015. http://hdl.handle.net/10803/300902.

Full text

Abstract:

Amphibians are a group in worldwide decline. The factors that are causing this decline are not well known, but could be multifactorial, related to the recent expansion of pathogens and habitat disturbance. One of these factors related to the loss of habitat quality is the introduction of alien species. These species can compete with or prey on species of the recipient community, producing deep changes in the structure of these communities. For this reason it is a priority to know which factors act by facilitating the invasion process and which species could be more affected by the presence of this alien species. In Catalonia has become established an alien frog, the painted frog. Introduced in the extreme south of France in the early XXth century, this species has expanded gradually, reaching the Llobregat delta to the south and Llanguedoc to the north. This region is rich in native species of amphibians, some of them endemic, and therefore it is necessary to know how this newcomer species interacts with each of these species. We have used a novel approach when analyzing these interactions, applying the theory of morphospaces. The morphospace is the range of morphological variation observed within a community. This morphology is correlated with the use of a niche, and hence the morphological similarities between the invasive and native species serve as a proxy to assess the functional overlap. These analogies in morphospace were evaluated also in the area of native species and among other species of Discoglossus. The question asked is "Does the invasive species occupy a vacant niche, maintaining a similar morphological gap than that observed in the source assemblage and in the case of other species of the genus Discoglossus?”.
Els amfibis són un grup en declivi a nivell mundial. Els factors que estan causant aquest declivi no són coneguts, però podria ser multifactorial, en relació amb l'expansió recent de certs patògens i les alteracions dels hàbitats. Un d'aquests factors que es relacionen amb la pèrdua de qualitat dels hàbitats és la introducció d'espècies exòtiques. Aquestes espècies poden competir o depredar sobre les espècies de la comunitat recipient, produint profundes alteracions en l'estructura d'aquestes comunitats. Per aquesta raó és prioritari conèixer que factors actuen facilitant el procés invasiu i quines espècies es poden veure més afectades per la presència d'una espècie exòtica. A Catalunya s'ha establert una espècie de anur d'origen africà, la granota pintada. Introduïda a l'extrem sud de França a inicis del segle XX, aquesta espècie s'ha anat expandint de forma progressiva, fins a arribar pel sud al delta del Llobregat i pel nord el Llenguadoc. Aquesta regió és rica en espècies natives d'amfibis, algunes d'elles endèmiques, i per tant cal conèixer com interacciona aquesta espècie recent arribada amb cadascuna d'aquestes espècies. Nosaltres hem utilitzat un enfocament nou en el moment d'analitzar aquestes interaccions, aplicant la teoria dels morfoespais. El morfoespai és el rang de variació morfològica que s'observa dins d'un acoblament. Aquesta morfologia es correlaciona amb l'ús d'un nínxol, i per tant les analogies morfològiques entre l'espècie invasora i les espècies natives poden servir com una aproximació per valorar el solapament funcional. Aquestes analogies en el morfoespai s'han avaluat també en l'area nativa de l'espècie i entre altres espècies de Discoglossus. La pregunta formulada és "ocupa l'espècie invasora un nínxol vacant, mantenint una distància morfològica similar que a l'acoblament d'origen i que altres espècies del gènere Discoglossus?".

APA, Harvard, Vancouver, ISO, and other styles

34

Mestre, Frederico Manuel Vaz Pontes Vitorino. "Synergistic effects of climate change and habitat fragmentation on species range shifts and metapopulation persistence." Doctoral thesis, Universidade de Évora, 2017. http://hdl.handle.net/10174/21118.

Full text

Abstract:

The effects of climate and landscape change on biodiversity have been widely acknowledged. However, there is still limited understanding on how the interaction among these processes affects species persistence over large spatial scales. This thesis aims to study the synergistic effects of climate and landscape change on species persistence and range shift dynamics. Using the Cabrera vole as model species, and combining ecological niche modeling (ENM), non-invasive genetic analysis and field sampling at predicted range margins, it is shown that forecasting range shifts of metapopulations under climate change, should require detailed sampling at the extremes of the ecological niche and that combining these three techniques allows an effective assessment of the niche. Analysis of metapopulation persistence and range expansion under landscape and climate change involved the development of an R package, ‘MetaLandSim’. This package offers a set of simulation tools integrating concepts from metapopulation and graph theories, providing an opportunity for testing ecological theories and evaluating species responses to environmental change. A first example of the package use is demonstrated by combining ENM projections with dispersal models (DM) considering three different connectivity scenarios. It is clearly demonstrated that combining range shift with lower connectivity will result in narrower range sizes for the Cabrera vole, highlighting the relevance of both, climate change and landscape connectivity in range dynamics evaluation. Finally, ‘MetaLandSim’ was used to test the hypothesis that intermediate levels of landscape disturbance may increase species persistence under certain species and landscape traits. Using a set of 54 virtual species differing in their ecological traits, it is shown that species with mid to higher dispersal and early successional preferences were more likely to benefit from intermediate disturbance. Overall, this study provides important insights for improving predictions on metapopulation persistence and range dynamics under various scenarios of landscape and climate change; Efeitos sinergéticos das alterações climáticas e fragmentação de habitat na distribuição das espécies e persistência metapopulacional Resumo: Os efeitos das alterações de paisagem e climáticas são reconhecidos na literatura científica. Esta tese tem por objetivo contribuir para a clarificação e compreensão dos efeitos sinergéticos das alterações climáticas e de paisagem na persistência das metapopulações e na alteração das áreas de distribuição das espécies. Usando o ratode- Cabrera como modelo, e combinando a modelação de nicho ecológico (ENM) com técnicas de genética não-invasiva e amostragens de campo nas margens da área de distribuição, demonstra-se a combinação das três técnicas e a inclusão de amostras nos extremos do nicho ecológico tornam mais eficaz que a previsão das novas áreas de distribuição num contexto de alterações climáticas. A análise da persistência metapopulacional e da expansão da área de distribuição em condições de alterações ambientais envolveu o desenvolvimento do package de R ‘MetaLandSim’. Este oferece um conjunto de ferramentas de simulação combinando as teorias dos grafos e metapopulações, o que permite testar teorias ecológicas e avaliar respostas das espécies às alterações ambientais. Usa-se este package para gerar modelos de dispersão (DM) que consideram simultaneamente a conectividade da paisagem e capacidade de dispersão. Estes DM, com três cenários de conectividade, foram projetados para o futuro e combinados com as projeções dos ENM. Demonstra-se que a perda de conectividade, associada à movimentação da janela climática, terá reduzirá a área de distribuição do rato-de-Cabrera. Finalmente, o ‘MetaLandSim’ é usado para testar a hipótese de que níveis intermédios de perturbação da paisagem podem beneficiar algumas espécies. Foram usadas 54 espécies virtuais com diferentes características ecológicas demonstrando que espécies com dispersões médias a elevadas e preferência por manchas nos primeiros estados da sucessão beneficiam de níveis intermédios de dinamismo. Este estudo fornece informação relevante para melhorar previsões da persistência das metapopulações e das dinâmicas das áreas de distribuição sob diversos cenários de alterações ambientais.

APA, Harvard, Vancouver, ISO, and other styles

35

Wu, Yunke. "Molecular phylogenetics, morphological evolution, and speciation of Chinese stout newts (Salamandridae: Pachytriton)." Thesis, Harvard University, 2013. http://dissertations.umi.com/gsas.harvard:10714.

Full text

Abstract:

China harbors 10% of the world's salamander species. Studying their evolutionary history provides critical insights into the evolution of the fauna of the Far East. The stout newts (Pachytriton, also known as paddle-tailed newts) are a genus of aquatic montane salamanders that are widely distributed in southeastern China. Despite their longstanding popularity among the global pet trade, little is known of their biology beyond external morphology. My thesis presents the first systematic study to elucidate phylogenetic relationships, character evolution, biogeographic patterns, species delimitation, and speciation mechanisms in this genus.

APA, Harvard, Vancouver, ISO, and other styles

36

Bobrowski, Maria [Verfasser], and Udo [Akademischer Betreuer] Schickhoff. "Modelling the ecological niche of a treeline species (Betula utilis) in the Himalayan region / Maria Bobrowski ; Betreuer: Udo Schickhoff." Hamburg : Staats- und Universitätsbibliothek Hamburg, 2018. http://d-nb.info/1173899235/34.

Full text

APA, Harvard, Vancouver, ISO, and other styles

37

Kozak, Kenneth H., and John J. Wiens. "What explains patterns of species richness? The relative importance of climatic-niche evolution, morphological evolution, and ecological limits in salamanders." WILEY-BLACKWELL, 2016. http://hdl.handle.net/10150/621556.

Full text

Abstract:

A major goal of evolutionary biology and ecology is to understand why species richness varies among clades. Previous studies have suggested that variation in richness among clades might be related to variation in rates of morphological evolution among clades (e.g., body size and shape). Other studies have suggested that richness patterns might be related to variation in rates of climatic-niche evolution. However, few studies, if any, have tested the relative importance of these variables in explaining patterns of richness among clades. Here, we test their relative importance among major clades of Plethodontidae, the most species-rich family of salamanders. Earlier studies have suggested that climatic-niche evolution explains patterns of diversification among plethodontid clades, whereas rates of morphological evolution do not. A subsequent study stated that rates of morphological evolution instead explained patterns of species richness among plethodontid clades (along with "ecological limits" on richness of clades, leading to saturation of clades with species, given limited resources). However, they did not consider climatic-niche evolution. Using phylogenetic multiple regression, we show that rates of climatic-niche evolution explain most variation in richness among plethodontid clades, whereas rates of morphological evolution do not. We find little evidence that ecological limits explain patterns of richness among plethodontid clades. We also test whether rates of morphological and climatic-niche evolution are correlated, and find that they are not. Overall, our results help explain richness patterns in a major amphibian group and provide possibly the first test of the relative importance of climatic niches and morphological evolution in explaining diversity patterns.

APA, Harvard, Vancouver, ISO, and other styles

38

Williams, Alison Kay. "The influence of probability of detection when modeling species occurrence using GIS and survey data." Diss., Virginia Tech, 2000. http://hdl.handle.net/10919/11129.

Full text

Abstract:

I compared the performance of habitat models created from data of differing reliability. Because the reliability is dependent on the probability of detecting the species, I experimented to estimate detectability for a salamander species. Based on these estimates, I investigated the sensitivity of habitat models to varying detectability. Models were created using a database of amphibian and reptile observations at Fort A.P. Hill, Virginia, USA. Performance was compared among modeling methods, taxa, life histories, and sample sizes. Model performance was poor for all methods and species, except for the carpenter frog (Rana virgatipes). Discriminant function analysis and ecological niche factor analysis (ENFA) predicted presence better than logistic regression and Bayesian logistic regression models. Database collections of observations have limited value as input for modeling because of the lack of absence data. Without knowledge of detectability, it is unknown whether non-detection represents absence. To estimate detectability, I experimented with red-backed salamanders (Plethodon cinereus) using daytime, cover-object searches and nighttime, visual surveys. Salamanders were maintained in enclosures (n = 124) assigned to four treatments, daytime__low density, daytime__high density, nighttime__low density, and nighttime__high density. Multiple observations of each enclosure were made. Detectability was higher using daytime, cover-object searches (64%) than nighttime, visual surveys (20%). Detection was also higher in high-density (49%) versus low-density enclosures (35%). Because of variation in detectability, I tested model sensitivity to the probability of detection. A simulated distribution was created using functions relating habitat suitability to environmental variables from a landscape. Surveys were replicated by randomly selecting locations (n = 50, 100, 200, or 500) and determining whether the species was observed, based on the probability of detection (p = 40%, 60%, 80%, or 100%). Bayesian logistic regression and ENFA models were created for each sample. When detection was 80 __ 100%, Bayesian predictions were more correlated with the known suitability and identified presence more accurately than ENFA. Probability of detection was variable among sampling methods and effort. Models created from presence/absence data were sensitive to the probability of detection in the input data. This stresses the importance of quantifying detectability and using presence-only modeling methods when detectability is low. If planning for sampling as an input for suitability modeling, it is important to choose sampling methods to ensure that detection is 80% or higher.
Ph. D.

APA, Harvard, Vancouver, ISO, and other styles

39

Larish, Penny Mae. "An analysis of fish consumption in Winnipeg with identification of potential niche markets for freshwater fish species native to Manitoba." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0007/MQ41661.pdf.

Full text

APA, Harvard, Vancouver, ISO, and other styles

40

Karst, Justine. "Ecological separation among fern species in an old-growth forest." Thesis, McGill University, 2001. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=33790.

Full text

Abstract:

The validity of niche-assembly rules in explaining community structure is revisited by testing for ecological separation among ferns. An intensive, fine-scale survey of fern abundance and environmental variation was done in 1-ha of old-growth forest. Three methods of detecting niche segregation (canonical correspondence analysis, detrended correspondence analysis and GIS mapping) suggested that most fern species at the site are distributed according to distinct environmental preferences. The most important gradients separating fern species are first, the amount of soil moisture and second, soil nitrate concentration. Contrary to other findings, pH had little influence on controlling fern distribution. Spatial autocorrelation, detected by partialled ordinations, obscured the presence of niche partitioning. As well, sampling grain changed the apparent location of some species on environmental gradients and their ecological similarity to other species. Finer-scaled environmental heterogeneity or dispersal-mediated processes may account for the unexplained variation in fern species abundance of this site.

APA, Harvard, Vancouver, ISO, and other styles

41

Li, Yuanzhi. "Structure et dynamique d'occupation de l'espace fonctionnel à travers des gradients spatiaux et temporels." Thèse, Université de Sherbrooke, 2017. http://hdl.handle.net/11143/11615.

Full text

Abstract:

Les modèles d'occupation de niche au sein des communautés locales, la variabilité spatiale de la biodiversité le long des gradients environnementaux du stress et des perturbations, et les processus de succession végétale sont plusieurs sujets fondamentaux en écologie. Récemment, l'approche basée sur les traits est apparue comme un moyen prometteur de comprendre les processus structurant les communautés végétales et cette approche a même été proposée comme méthode pour reconstruire l'écologie communautaire en fonction des traits fonctionnels. Par conséquent, lier ces thèmes fondamentaux en utilisant une lentille fonctionnelle devrait nous donner un aperçu de certaines questions fondamentales en écologie et sera l'objectif principal de ma thèse. En général, mon projet de doctorat vise à étudier les structures de l'occupation de l'espace fonctionnel dans les gradients spatio-temporels. Plus précisément, l'objectif du chapitre 2 est (i) d'étudier les modèles d'occupation de la niche fonctionnelle en calculant trois métriques clés de niche (le volume total de niche fonctionnelle , le chevauchement des niches fonctionnelles et le volume de niche fonctionnel moyen) des communautés pauvres en espèces aux communautés riches en espèces et (ii) de déterminer le principal facteur de la structure observée de l'occupation de la niche fonctionnelle dans les communautés végétales du monde entier. Dans le chapitre 3, je vise à prédire et à expliquer la variation de la richesse en espèces selon les gradients de stress et de perturbation, en reliant le modèle d'équilibre dynamique et l'occupation de la niche fonctionnelle en fonction du cadre développé au chapitre 2. L'objectif du chapitre 4 est de tester expérimentalement l’application d'une méthode d'ordination CSR évaluée globalement en fonction de trois traits de feuilles (surface foliaire, teneur en matière sèche des feuilles et surface foliaire spécifique) dans les études locales. Enfin, l'objectif du chapitre 5 est de tester expérimentalement les hypothèses qui concilient les points de vue déterministes et historiquement contingents de la succession végétale, en étudiant la variation des divergences taxonomiques et fonctionnelles entre les communautés selon des gradients de stress et de perturbation. L'étude globale (chapitre 2) est basée sur une collection de 21 jeux de données, couvrant les biomes tropicaux et tempérés, et se compose de 313 communautés végétales représentant différentes formes de croissance. Les études locales (chapitre 3, 4 et 5) sont basées sur le même système expérimental constitué de 24 mésocosmes présentant différents niveaux de stress et de perturbation. L'expérience a commencé en 2009 avec le même mélange de graines de 30 espèces herbacées semées sur les 24 mésocosmes et s'est terminée en 2016. Nous avons permis la colonisation naturelle de graines de la banque commune de graines de sol et de l'environnement pendant la succession de sept ans. Dix traits ont été mesurés sur cinq individus (échantillonnés directement à partir des mésocosmes) par espèce par mésocosme en 2014 (chapitre 3 et 4). Un autre ensemble de traits (16 traits, y compris certains traits qui ne pouvaient pas être mesurés directement dans les mésocosmes), ont été mesurés au niveau de l'espèce (valeurs moyennes des traits) pour les 34 espèces les plus abondantes (certaines espèces disparues dans les mésocosmes) au cours des sept Ans, en les regroupant séparément pour une saison de croissance. Au chapitre 2, nous avons constaté que les communautés étaient plus diverses en termes fonctionnels (une augmentation du volume fonctionnel total) dans les communautés riches en espèces et que les espèces se chevauchaient davantage au sein de la communauté (augmentation du chevauchement fonctionnel), mais ne divisaient pas plus finement l'espace fonctionnel (aucune réduction du volume fonctionnel moyen). En outre, le filtrage de l'habitat est un processus répandu qui conduit à la caractérisation de l'occupation de niche fonctionnelle dans les communautés végétales. Dans le chapitre 3, nous avons trouvé un modèle similaire d'occupation de niche fonctionnelle sur un système expérimental avec une taille spatiale communautaire constante et un effort d'échantillonnage des traits, qui, avec le chapitre 2, nous a fourni une image plus complète et plus solide de l'occupation de niche fonctionnelle dans les communautés végétales. De plus, nous avons réussi à relier le modèle de l'occupation de la niche fonctionnelle et le modèle d'équilibre dynamique et avons constaté que le filtrage concurrentiel était le processus dominant qui détermine le mode d'occupation de la niche fonctionnelle et la richesse des espèces le long du stress et de la perturbation des gradients. Au chapitre 4, nous fournissons un soutien empirique à une méthode d'ordination CSR calibrée globalement en montrant une relation entre l'abondance relative d'espèces en croissance dans les mésocosmes ayant différents niveaux de fertilité du sol et mortalité indépendante de la densité et leur classification CSR. Au chapitre 5, nous avons montré que la succession d'installations au cours de sept ans dans ces mésocosmes était plus déterministe d'un point de vue fonctionnel, mais plus historiquement contingent d'un point de vue taxonomique et que l'importance relative de la contingence historique a diminué à mesure que l'environnement devenait plus stressé ou perturbé. En conclusion, les structures de l'occupation de l'espace fonctionnel dans (le volume fonctionnel total, le chevauchement fonctionnel et le volume fonctionnel moyen, les Chapitre 2 et 3) ou entre les communautés locales (dissimilarité fonctionnelle, chapitre 5) sont déterministes plutôt que neutres (ou contingence historique ). Les espèces tolératrices de stress sont plus avantagées dans les mésocosmes moins fertiles tandis que les espèces rudérales sont plus avantagées dans les mésocosmes avec plus de mortalité indépendante de la densité.
Abstract : The patterns of niche occupancy within local communities, the spatial variability of biodiversity along environmental gradients of stress and disturbance, and the processes of plant succession are several fundamental topics in ecology. Recently, the trait-based approach has emerged as a promising way to understand the processes structuring plant communities and has even been proposed as a method to rebuild community ecology based on functional traits. Therefore, linking these fundamental themes through a functional lens should give us more insight into some basic questions in ecology and will be the main objective of my thesis. Generally, my PhD project is to investigate the structures of functional space occupancy along both spatial and temporal gradients. Specifically, the objective of Chapter 2 is to investigate the patterns of functional niche occupancy by calculating three key niche metrics (the total functional niche volume, the functional niche overlap and the average functional niche volume) from speciespoor communities to species-rich communities and to determine the main driver of the observed pattern of functional niche occupancy across plant communities worldwide. In Chapter 3, I aim to predict and explain the variation of species richness along gradients of stress and disturbance, by linking the dynamic equilibrium model and functional niche occupancy based on the framework developed in Chapter 2. The objective of Chapter 4 is to experimentally test the application of a globally calibrated CSR ordination method based on three leaf traits (leaf area, leaf dry matter content and specific leaf area) in local studies. Finally, the aim of Chapter 5 is to experimentally test the hypotheses reconciling the deterministic and historically contingent views of plant succession, by investigating the variation of taxonomic and functional dissimilarities between communities along gradients of stress and disturbance. The global study (Chapter 2) is based on a collection 21 trait datasets, spanning tropical to temperate biomes, and consisting of 313 plant communities representing different growth forms. The local studies (Chapter 3, 4 and 5) are based on the same experimental system consisting of 24 mesocosms experiencing different levels of stress and disturbance. The experiment started in 2009 with the same seed mixture of 30 herbaceous species broadcast over the 24 mesocosms and ended in 2016. We allowed natural colonization of seeds from the common soil seed bank and from the surroundings during the seven-year succession. Ten traits were measured on five individuals (sampled directly from the mesocosms) per species per mesocosms in 2014 (Chapter 3 and 4). Another set of traits (16 traits including some traits that were not able to measured directly in the mesocosms) were measured at the species level (species mean traits values) for the 34 most abundant species (some species disappeared in the mesocosms) over the seven years, by regrowing them separately for one growing season. In Chapter 2, we found communities were more functionally diverse (an increase in total functional volume) in species-rich communities, and species overlapped more within the community (an increase in functional overlap) but did not more finely divide the functional space (no decline in average functional volume). Moreover, habitat filtering is a widespread process driving the pattern of functional niche occupancy across plant communities. In Chapter 3, we found a similar pattern of functional niche occupancy on an experimental system with a constant community spatial size and trait-sampling effort, which together with Chapter 2 provided us a more comprehensive and robust picture of functional niche occupancy across plant communities. In addition, we succeeded in linking the pattern of functional niche occupancy and the dynamic equilibrium model and found that habitat filtering was the dominant process determining the pattern of functional niche occupancy and species richness along the gradients stress and disturbance. In Chapter 4, we provide empirical support for a globally calibrated CSR ordination method by showing a relationship between the relative abundance of species growing in mesocosms having different levels of soil fertility and density-independent mortality and their CSR classification. In Chapter 5, we showed that plant succession over seven years in these mesocosms was more deterministic from a functional perspective but more historically contingent from a taxonomic perspective, and that the relative importance of historical contingency decreased as the environment became more stressed or disturbed. In conclusion, the structures of functional space occupancy within (the total functional volume, the functional overlap and the average functional volume; Chapter 2 and 3) or between local communities (functional dissimilarity, Chapter 5) are deterministic rather than neutral (or historical contingency). Stress-tolerators were more favored in high stress communities, while ruderals are more favored in high disturbed mesocosms (Chapter 4).

APA, Harvard, Vancouver, ISO, and other styles

42

Bieleveld, Michel Jan Marinus. "Improving species distribution model quality with a parallel linear genetic programming-fuzzy algorithm." Universidade de São Paulo, 2016. http://www.teses.usp.br/teses/disponiveis/3/3141/tde-26012017-113329/.

Full text

Abstract:

Biodiversity, the variety of life on the planet, is declining due to climate change, population and species interactions and as the result f demographic and landscape dynamics. Integrated model-based assessments play a key role in understanding and exploring these complex dynamics and have proven use in conservation planning. Model-based assessments using Species Distribution Models constitute an efficient means of translating limited point data to distribution probability maps for current and future scenarios in support of conservation decision making. The aims of this doctoral study were to investigate; (1) the use of a hybrid genetic programming to build high quality models that handle noisy real-world presence and absence data, (2) the extension of this solution to exploit the parallelism inherent to genetic programming for fast scenario based decision making tasks, and (3) a conceptual framework to share models in the hope of enabling research synthesis. Subsequent to this, the quality of the method, evaluated with the true skill statistic, was examined with two case studies. The first with a dataset obtained by defining a virtual species, and the second with data extracted from the North American Breeding Bird Survey relating to mourning dove (Zenaida macroura). In these studies, the produced models effectively predicted the species distribution up to 30% of error rate both presence and absence samples. The parallel implementation based on a twenty-node c3.xlarge Amazon EC2 StarCluster showed a linear speedup due to the multiple-deme coarse-grained design. The hybrid fuzzy genetic programming algorithm generated under certain consitions during the case studies significantly better transferable models.
Biodiversidade, a variedade de vida no planeta, está em declínio às alterações climáticas, mudanças nas interações das populações e espécies, bem como nas alterações demográficas e na dinâmica de paisagens. Avaliações integradas baseadas em modelo desempenham um papel fundamental na compreensão e na exploração destas dinâmicas complexas e tem o seu uso comprovado no planejamento de conservação da biodiversidade. Os objetivos deste estudo de doutorado foram investigar; (1) o uso de técnicas de programação genética e fuzzy para construir modelos de alta qualidade que lida com presença e ausência de dados ruidosos do mundo real, (2) a extensão desta solução para explorar o paralelismo inerente à programação genética para acelerar tomadas de decisão e (3) um framework conceitual para compartilhar modelos, na expectativa de permitir a síntese de pesquisa. Subsequentemente, a qualidade do método, avaliada com a true skill statistic, foi examinado com dois estudos de caso. O primeiro utilizou um conjunto de dados fictícios obtidos a partir da definição de uma espécie virtual, e o segundo utilizou dados de uma espécie de pomba (Zenaida macroura) obtidos do North American Breeding Bird Survey. Nestes estudos, os modelos foram capazes de predizer a distribuição das espécies maneira correta mesmo utilizando bases de dados com até 30% de erros nas amostras de presença e de ausência. A implementação paralela utilizando um cluster de vinte nós c3.xlarge Amazon EC2 StarCluster, mostrou uma aceleração linear devido ao arquitetura de múltiplos deme de granulação grossa. O algoritmo de programação genética e fuzzy gerada em determinadas condições durante os estudos de caso, foram significativamente melhores na transferência do que os algoritmos do BIOMOD.

APA, Harvard, Vancouver, ISO, and other styles

43

Bourguignon, Thomas. "The Anoplotermes group in French Guiana :systematics, diversity and ecology." Doctoral thesis, Universite Libre de Bruxelles, 2010. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/210132.

Full text

Abstract:

Les termites forment un groupe animal important en milieu tropical, où leur richesse spécifique est plus élevée que dans n’importe quel autre écosystème. Ils se nourrissent de matière organique végétale à différent état de décomposition, du bois dur à la matière organique minérale du le sol. Cette diversification du régime alimentaire ne se produit que chez les Termitidae, parfois appelés « termites supérieurs », alors que les autres familles se nourrissent exclusivement de bois ou d’herbe. Les termites humivores sont extrêmement abondants en Amérique du Sud et en Afrique tropicale, mais sont relativement peu étudiés par rapport aux termites xylophages. C’est particulièrement vrai pour le groupe Anoplotermes, qui représente le groupe de termites le moins bien connu. Ce travail vise à faire la lumière sur l’écologie et la diversité de ce groupe strictement humivore, et comprend les sections suivantes :(1) Des échantillonnages standardisés dans sept sites de Guyane Française ont révèle, avec quelques exceptions, que les termites xylophages sont relativement peu spécialisés à un site. Au contraire, les espèces du groupe Anoplotermes, ainsi que les termites humivores en général, sont spécialisés à un type de forêt. Cette spécialisation contribue plus que probablement à la diversification écologique, et donc, à une augmentation de la richesse spécifique des termites humivores. (2) En utilisant les ratios d’isotopiques δ13C et δ15N, nous avons aussi trouvé qu’il existe une spécialisation des espèces le long d’un gradient d’humification chez le groupe Anoplotermes, de l’interface entre le bois pourri et le sol au sol pauvre en matière organique. Donc, au moins deux facteurs favorisent la richesse spécifique du groupe Anoplotermes dans le sol, malgré le manque d’évidence pour une séparation spatiale et temporelle entre les espèces. Cette spécialisation spécifique réduit la compétition interspécifique aux espèces se nourrissant de matière organique au même état de décomposition. (3) Ce mécanisme n’est probablement pas restreint aux espèces du groupe Anoplotermes et le ratio isotopique δ15N varie considérablement entre les termites humivores de manière générale. Les termites humivores comptent des espèces avec des régimes alimentaires différents ne partageant pas toujours les mêmes niches écologiques. Cette diversification du régime alimentaire ne c’est pas produit de manière aléatoire durant l’évolution des termites et les espèces proches tendent à se nourrir du même substrat. (4) Au niveau intraspécifique, il semble que la compétition contraigne la dynamique des colonies. En effet, chez A. banksi, nous avons trouvé que les nids matures sont surdispersés. Les nouveaux nids se trouvent principalement à une certaine distance des nids établis, plus particulièrement dans les trous laissés par les nids morts. Si ce patron est le résultat d’une sélection des sites de nidification, ou plutôt d’une exclusion compétitive reste sujet à discussion, mais met néanmoins en évidence la présence de compétition chez les termites humivores du groupe Anoplotermes. (5) Au vu de la richesse spécifique locale du groupe Anoplotermes, le nombre d’espèces décrites reste remarquablement bas. Après inspection du matériel type, seuls 30 espèces du groupe se sont avérés valides en Amérique du Sud, alors que 80% des espèces que nous avons collectées sont nouvelles pour la science. Cette disproportion entre ce qui est connu et la diversité réelle du groupe, met en évidence le besoin de réaliser des études supplémentaires pour améliorer la connaissance de ce groupe peu connu, le groupe Anoplotermes.
Doctorat en Sciences
info:eu-repo/semantics/nonPublished

APA, Harvard, Vancouver, ISO, and other styles

44

Kantelis, Theron Michael. "Black Bears (Ursus americanus) versus Brown Bears (U. arctos): Combining Morphometrics and Niche Modeling to Differentiate Species and Predict Distributions Through Time." Digital Commons @ East Tennessee State University, 2017. https://dc.etsu.edu/etd/3262.

Full text

Abstract:

Late Pleistocene American black bears (Ursus americanus) often overlap in size with Pleistocene brown bears (U. arctos), occasionally making them difficult to diagnose. Large U. americanus have previously been distinguished from U. arctos by the length of the upper second molar (M2). However, the teeth of fossil U. americanus sometimes overlap size with U. arctos. As such, there is need for a more accurate tool to distinguish the two species. Here, 2D geometric morphometrics is applied to the occlusal surface of the M2 to further assess the utility of this tooth for distinguishing U. americanus and U. arctos specimens. When combined with an Ecological Niche Model of U. americanus and U. arctos in North America from the Last Glacial Maximum, this morphometric technique can be applied to key regions. A case of two Pleistocene specimens previously identified as U. arctos from eastern North America exemplifies the utility of this combination.

APA, Harvard, Vancouver, ISO, and other styles

45

Karlson, Agnes M. L. "Benthic use of phytoplankton blooms uptake, burial and biodiversity effects in a species-poor system /." Doctoral thesis, Stockholm : Department of Systems Ecology, Stockholm University, 2010. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-32598.

Full text

Abstract:

Diss. (sammanfattning) Stockholm : Stockholms universitet, 2010.
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 2: Manuscript. Paper 4: In press. Paper 5: Manuscript. Härtill 5 uppsatser.

APA, Harvard, Vancouver, ISO, and other styles

46

Hylin, Anna. "Didaktiska arter." Thesis, Södertörns högskola, Institutionen för livsvetenskaper, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:sh:diva-17233.

Full text

Abstract:

The study intends to find easily recognizable indicator species for water quality in the constructed wetland of Flemingsbergsviken. The study is relevant since indicator species can be difficult to determine for common people. Easily recognizable indicator species could improve dialogue between the scientific community, administrative authorities and the general public. Such species could be used in education systems, associations or in information campaigns. Therefore, I have chosen to refer to these species as didactical species. Water quality was examined by measuring conductivity, pH and oxygen content in relation to distance from the wetland inlet. The results demonstrate a significant correlation between conductivity and distance. Species occupy different ecological niches and distribution patterns of species in the wetland can be expected to follow changes in abiotic factors, such as water quality. Potential indicator species were investigated by inventorying twelve species of plants and animals. The results show significant linear or curvilinear correlations between one or several water quality factors and the species reedmace, common reed, yellow iris, freshwater woodlouse, twisted ramshorn, damsel- and dragonfly larvae. By carrying out a questionnaire aimed at a group of adults and by talking to a group of children, conclusions could be made regarding indicator species that were easy to recognize and associate to. The results demonstrate that adults found common reed and reedmace most easy to recognize while children found the freshwater woodlouse most interesting. Thus, these indicator species for water quality can be included in the concept didactical species.
Studien syftar till att finna indikatorarter för vattenkvalitet i Flemingsbergsvikens våtmarksanläggning som är lätta att känna igen och associera till. Studien är relevant då indikatorarter kan vara svårbestämda för gemene man. Arter som är lättigenkännbara skulle kunna förbättra dialog mellan forskarsamhället, allmänheten och myndigheter och kan användas i utbildningssyfte inom skolor, föreningar eller i informationskampanjer. Jag har därför valt att kalla arterna för didaktiska arter. Vattenkvalitet undersöktes genom att mäta konduktivitet, pH och syrgashalt i förhållande till avstånd från inlopp. Resultaten visade att det finns ett signifikant samband mellan konduktivitet och avstånd. Eftersom arter upptar olika ekologiska nischer kan artutbredningsmönstret i våtmarken förväntas följa förändringar i abiotiska faktorer, såsom vattenkvalitet. Potentiella indikatorarter undersöktes genom att inventera tolv växt- och djurarter i anläggningen. Resultaten visar signifikanta linjära eller kurvlinjära samband med en eller flera utav vattenkvalitetsfaktorerna och arterna bredkaveldun, vass, gul svärdslilja, sötvattengråsugga, remskivsnäcka samt trollsländelarver. Genom en enkätundersökning för en grupp vuxna samt samtal med en grupp förskolebarn kunde det dras slutsatser om vilka av indikatorarterna för vattenkvalitet som var lättast att känna igen och associera till. Resultaten visar att de vuxna upplevde vass och bredkaveldun som lättast att känna igen medan barnen upplevde att sötvattengråsugga var mest intressant. Dessa indikatorarter för vattenkvalitet kan således inkluderas i begreppet didaktiska arter.

APA, Harvard, Vancouver, ISO, and other styles

47

Serebryakova, Alexandra. "Acclimation and adaptation of invasive seaweeds - a case study with the brown alga sargassum muticum." Thesis, Paris 6, 2017. http://www.theses.fr/2017PA066475.

Full text

Abstract:

Les algues non-indigènes ont des impacts sur les communautés naturelles à une échelle mondiale: elles affectent la biodiversité et le fonctionnement des écosystèmes ainsi que les services écosystémiques, avec des conséquences économiques et sociales. Parmi les conséquences de ces introductions sont le déplacement d'espèces indigènes, des compétitions avec des espèces en danger et des effets sur les trajectoires éco-évolutives des espèces des communautés envahies. Bien que crucial pour anticiper le devenir des espèces non-indigènes, comprendre les mécanismes d'acclimatation et d'adaptation agissant post-introduction reste un challenge chez les algues. Au cours de cette thèse, nous avons étudié certains processus d'acclimatation, en particulier le rôle des bactéries associées, et leurs effets, en utilisant comme modèle d'étude Sargassum muticum. Cette algue brune originaire d'Asie, est une espèce emblématique parmi les algues introduites avec une présence du Mexique à l'Alaska en Amérique et du Maroc à la Norvège en Europe. Nous avons effectué une analyse bibliographique des traits et caractéristiques écologiques qui pourraient expliquer son succès. Nous avons ensuite montré que l'acidification n'a pas d'effets significatifs sur les bacteries associées, bien que des changements saisonniers du microbiome aient été observés. Enfin, nous avons utilisé un modèle de niche écologique, intégrant la phénologie, pour prédire la distribution de S. muticum sous deux scénarios de changement climatique. Selon nos résultats, d'ici 2100, la distribution de S. muticum devrait se déplacer vers le nord dans l'hémisphère nord avec des régressions dans certaines zones actuellement occupées
Non-indigenous seaweeds impact natural communities worldwide, affecting biodiversity, ecosystem functioning, and ecosystem services, resulting in significant economic and social consequences. Among major impacts are the displacement of native species, a threat to endangered species, and effects on ecological and evolutionary processes within the invaded communities. While critical to predict the fate of introduced species, understanding the mechanisms of acclimation and adaptation following introduction represents a great challenge in seaweeds. In this thesis, we investigated some acclimation processes, with an emphasis on the role of associated microbiota, and examined their effects with Sargassum muticum as a model species. This brown seaweed native to Asia, is an emblematic invader among seaweeds, with a distribution now ranging from Mexico to Alaska in America and from Morocco to Norway in Europe. We first reviewed the competitive advantages and traits that may contribute to its invasiveness. We then showed that acidification has no significant effects on associated bacteria, although seasonal changes in the microbiome have been observed. Finally, we applied ecological niche modelling, but innovatively accounting for phenology, to project the distribution of S. muticum under two future climate change scenarios. According to our projections, by 2100 the distribution of S. muticum is expected to shift northwards along its European, North American and Asian distributions with partial retreat from the currently occupied areas

APA, Harvard, Vancouver, ISO, and other styles

48

Cavalin, Pedro Ortman 1980. "Estrutura de comunidades de espécies lenhosas ao longo de um gradiente de altitude na floresta ombrófila densa atlântica do sudeste brasileiro : uma abordagem filogenética e funcional." [s.n.], 2012. http://repositorio.unicamp.br/jspui/handle/REPOSIP/314891.

Full text

Abstract:

Orientador: Carlos Alfredo Joly
Tese (doutorado) - Universidade Estadual de Campinas, Instituto de Biologia
Made available in DSpace on 2018-08-20T14:31:26Z (GMT). No. of bitstreams: 1 Cavalin_PedroOrtman_D.pdf: 3253505 bytes, checksum: 2c0255c7d1c447ec6f4badb5c03b3993 (MD5) Previous issue date: 2012
Resumo: Um grande número de espécies co-ocorre em florestas tropicais. Diferenciação de nicho e processos estocásticos são invocados como mecanismos que possibilitam essa coexistência de espécies. Recentemente, métodos filogeneticamente explícitos ou com base em atributos funcionais (considerados bons indicadores de nicho de regeneração, história de vida e tolerância ambiental) vem sendo usados para analisar tais mecanismos. No presente trabalho, estudei comunidades de espécies lenhosas no sub-bosque ao longo de um gradiente de altitude na Floresta Ombrófila Densa (FOD) Atlântica no Parque Estadual da Serra do Mar, SP, tentando relacionar a estrutura de comunidades com variáveis ambientais, e se tais relações variam de acordo com a altitude. Analisamos a estrutura filogenética em três sítios localizados em diferentes cotas altitudinais (FOD de Terras Baixas, 70 m; FOD Submontana, 370 m; FOD Montana, 1070 m). Em nenhum dos sítios foi observada estruturação filogenética, tampouco relações da estrutura filogenética com variáveis ambientais. Em seguida, analisamos a estrutura de comunidade baseada em atributos funcionais. Apesar de haver correlações entre atributos funcionais e variáveis ambientais no nível das espécies, as comunidades não apresentaram estrutura significativamente diferente do esperado pelo acaso, embora o conjunto de espécies comuns tenha apresentado boa correlação entre atributos funcionais e variáveis ambientais. Por fim, analisamos como a estrutura de comunidades, baseada em atributos funcionais, em um sítio (FOD Submontana) varia entre coortes de plantas de diferentes tamanhos. Em geral, plantas de menor tamanho são mais similares entre si do que o esperado pelo acaso, enquanto que plantas de maior tamanho não diferem do esperado pelo acaso. Quando árvores de dossel são analisadas em separado, nenhuma das classes de tamanho difere do esperado pelo acaso. Mortalidade causada pela abundância de vizinhos, e independente de suas identidades, pode ser responsável pela ausência de mudança na estrutura da comunidade baseada em atributos ao longo das coortes. Discutimos a ausência de variação na estruturação das comunidades ao longo do gradiente de altitude na FOD Atlântica, levando em consideração as características do mesmo, e propomos estratégias para o melhor entendimento da dinâmica dessas comunidades
Abstract: A large number of species co-occur in tropical forests. Niche differentiation and stochastic processes are commonly invoked to explain species co-occurrence. Recently, phylogenetically explicit or traitbased (functional traits are considered to be good proxies for regeneration niche, life history, and environmental tolerance) methods have been used to assess these mechanisms. In the present study, We have surveyed understory woody species communities along an altitudinal gradient on the Atlantic Dense Ombrophilous Forest at the Serra do Mar State Park, São Paulo State, Brazil, analyzing the relationships between community structure and environmental variables, and how these relationships vary along the gradient. Community phylogenetic structure was assessed in three sites differing in altitude (Lowland, 70 m; Lower Montane, 370 m; Montane, 1070 m). No phylogenetic structure was found in any site, nor correlations between phylogenetic structure and environmental variables. We then analyzed trait-based community structure. We observed no community structure, even though there were significant correlations between functional traits and environmental variables at specieslevel on a set of frequent species. Finally, we assessed how trait-based community structure varied between plant cohorts of differing sizes. In general, smaller plants were functionally more similar to each other than expected by chance, while larger plants showed no significant structuring. When only canopy trees are separately analyzed, no size-class cohort differs from the random expectation. This lack of change in structuring among cohorts may be due to mortality caused by neighboring stem density, irrespective of species identity. We then discuss the absence of community phylogenetic and functional structuring of understory woody plants communities along the altitudinal gradient on the Atlantic Forest, taking into account its peculiarities, and propose strategies that could advance the understanding of these communities' dynamics
Doutorado
Biologia Vegetal
Doutor em Biologia Vegetal

APA, Harvard, Vancouver, ISO, and other styles

49

Roberto, Vinicius Alberici. "Distribuição potencial e atual do tamanduá-bandeira (Myrmecophaga tridactyla) e indicação de áreas prioritárias para sua conservação." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/91/91131/tde-02052018-182256/.

Full text

Abstract:

O tamanduá-bandeira (Myrmecophaga tridactyla) se distribui amplamente ao longo da região Neotropical, porém é provável que esteja extinto da maior parte de sua extensão original, notadamente na América Central e nos limites austrais de sua distribuição. O táxon está ameaçado de extinção globalmente (IUCN) e também em âmbito nacional. Embora historicamente a espécie ocorra em todos os biomas brasileiros, hoje é considerada extinta nos Pampas, quase extinta na Mata Atlântica, sendo que na Caatinga sua presença necessita de confirmação e no Cerrado suas populações vem sofrendo drásticas reduções. Atualmente não há estudos de revisão da distribuição da espécie nos biomas brasileiros, tão pouco foi avaliado se as áreas mais adequadas à espécie estão sendo protegidas e o conhecimento existente é insuficiente para adotar estratégias de conservação adequadas. Dessa maneira, o presente estudo teve como principal objetivo modelar a distribuição potencial e atual do tamanduá-bandeira no Brasil e nos biomas brasileiros, a fim de identificar quais variáveis preditoras melhor explicam a ocorrência da espécie em diferentes escalas. Além disso, a partir dos modelos de distribuição atual, os biomas foram avaliados quanto à adequabilidade ambiental (i.e. probabilidade de presença) e foram realizadas uma análise de lacunas e a identificação de áreas prioritárias para a conservação. A distribuição potencial do tamanduá-bandeira foi melhor explicada em escala continental, por variáveis bioclimáticas (sazonalidade de temperatura e precipitação) e topográficas (altitude), enquanto que a distribuição atual foi bem explicada nas duas escalas, por variáveis de uso e cobertura da terra (porcentagens de cobertura arbórea, de silvicultura e de cana-de-açúcar). O Cerrado foi o bioma de maior adequabilidade ambiental à espécie, seguido da Amazônia, Pantanal, Mata Atlântica e Caatinga, sendo que não foram obtidos registros recentes para os Pampas. Menos de 10% da distribuição atual do tamanduá-bandeira no Cerrado e Pantanal encontra-se protegida por Unidades de Conservação, existindo uma lacuna parcial de conservação. Áreas prioritárias para a espécie incluem um corredor central no Cerrado, grande parte do Pantanal e áreas de transição (ecótonos) com outros biomas. Os resultados obtidos neste estudo permitiram preencher lacunas de conhecimento acerca da distribuição do tamanduá-bandeira, bem como dar suporte para o planejamento de sua conservação.
The giant anteater (Myrmecophaga tridactyla) is widely distributed throughout the Neotropical region, but is probably extinct from most of its range, notably in Central America and the southern limits of its distribution. The species is listed as Vulnerable on the IUCN and national Red Lists. Although historically present in all Brazilian biomes, there are no studies reviewing its distribution, nor has it been evaluated if the Brazilian federal conservation units are protecting the areas most suitable to the species. Thus, the aim of this study was to model the potential and current distribution of the giant anteater in Brazil and Brazilian biomes, to identify which predictor variables best explain the occurrence of the species at different scales. Current distribution models were used to evaluate the biomes environmental suitability (i.e. probability of presence) and a gap analyses were performed. Also, priority areas for conservation were identified. The potential distribution of the anteater was better explained on a continental scale by bioclimatic (seasonality of temperature and precipitation) and topographic (altitude) variables, while the current distribution was well predicted in both scales, by land cover variables (percentages of tree cover, silviculture, and sugarcane). The Cerrado was the biome of greater environmental suitability to the species, followed by the Amazon, the Pantanal, the Atlantic Forest and the Caatinga. No recent records were obtained for the Pampas. Conservation units protect less than 10% of the current distribution of the giant anteater in the Cerrado and Pantanal. Priority areas for the species include a central corridor in the Cerrado, much of the Pantanal and ecotones. The results obtained in this study helped to fill knowledge gaps on the distribution of the giant anteater in Brazil, supporting actions for its conservation.

APA, Harvard, Vancouver, ISO, and other styles

50

Kulhanek, Stefanie. "Investigating the use of invasion history, meta-analysis and niche-based models as tools for predicting the ecological impacts of introduced aquatic species." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=66655.

Full text

Abstract:

Biological invasions pose a major threat to global biodiversity. While there is increasing concern regarding the impacts caused by non-indigenous species (NIS), generalisable tools for predicting their ecological effects have yet to be developed. Several researchers have suggested that examining the previously documented effects of NIS, termed invasion history, can serve as a basis for forecasting future impacts. Yet, while predictive models for impact have been devel oped based on the invasion histories of several widespread invaders, the generalisability of such approaches has not been demonstrated. The severity of the impacts caused by NIS may vary as a function of their local abundance across invaded sites. Thus by estimating the expected abundance of introduced species, at potential recipient locations, we may be able to identify habitats which are particularly vulnerable to their effects. While ecological niche-based models (ENM) have often been used to predict the abundance of species within their native ranges, such approaches have rarely been applied to NIS. In this thesis I conduct an extensive literature review, using 19 aquatic species, and assess the utility of invasion history for predicting future impacts. I illustrate that, while for most NIS limited and heterogeneous data currently inhibits the development of quantitative predictions, invasion history can often reveal the type and direction of future impacts. Using one of these species, Cyprinus carpio, as a case study, I conduct a meta-analysis and demonstrate that, where data is available, models incorporating NIS biomass can explain a substantial amount of variation in the severity of impacts across invaded locations. I then develop neural network-based ENM to forecast both the occurrence and biomass of C. carpio in a portion of its invaded range, using monitoring data from Minnesota. I test the ability of the resulting models to gene
Les invasions biologiques posent un risque majeur pour la biodiversité mondiale. Malgré qu'il y ait un intérêt grandissant concernant les impacts causés par les espèces non indigènes (ENI), des outils de prédictions de leurs effets écologiques restent encore à être développés. Plusieurs chercheurs ont suggéré que l'étude des impacts antérieurs des ENI, nommé historique d'invasion, pourrait servir en tant que référence pour prédire leurs effets futurs. Et malgré que des modèles de prédictions aient été développés selon l'historique d'invasion de certaines espèces envahissantes notoires, la précision globale de tels outils reste à être démontrée. La sévérité des impacts causés par les ENI peut varier selon leur abondance à travers des milieux envahis. Ainsi, par la prédiction de l'abondance des ENI, à travers des sites potentiellement envahissables, nous devrions être en mesure d'identifier les habitats particulièrement vulnérables face à leurs effets. En dépit que les modèles de niches fondées écologiques (MNE) aient souvent été utilisés pour prédire l'abondance des espèces dans leur aire de répartition d'origine, de telles approches ont rarement été mises en application envers des ENI. Dans cette thèse, j'entreprends une revue étendue des publications scientifiques concernant les ENI. En utilisant 19 espèces aquatiques comme échantillon, j'évalue l'utilité de l'historique d'invasion comme outil pour prévoir leurs impacts futurs. Je démontre que la plupart des données sur les impacts des ENI sont restreintes et hétérogènes, limitant le développement des prédictions quantitatives, mais que l'historique d'invasion peut souvent révéler le type et la direction et des impacts futurs. En utilisant un de ces ENI, Cyprinus carpio, comme sujet d'étude, je conduis une méta analyse et démontre que, où les données sont disponibles, les mod

APA, Harvard, Vancouver, ISO, and other styles

Dissertations / Theses on the topic 'Species niche'

Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles