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Roney, Hillary Christine. "Competitive Exclusion of Cyanobacterial Species in the Great Salt Lake." Diss., CLICK HERE for online access, 2008. http://contentdm.lib.byu.edu/ETD/image/etd2476.pdf.
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Morghan, Kimberly Jo Reever. "Competitive interactions between native grasses and invasive species in California grasslands /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2004. http://uclibs.org/PID/11984.
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Ross, Pamela. "Caesium-137 uptake in two grass species and the effects of competitive ions." Thesis, University of Newcastle Upon Tyne, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.389595.
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ICENHOUR, CRYSTAL RENEE PERRY. "EXPERIMENTAL EVIDENCE FOR COMPETITIVE COEXISTENCE OF TWO SPECIES OF PNEUMOCYSTIS WITHIN RAT LUNGS." University of Cincinnati / OhioLINK, 2002. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1012244966.
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Thomas, Heather M. "Competitive Interactions Between a Native and Exotic Trout Species in High Mountain Streams." DigitalCommons@USU, 1996. https://digitalcommons.usu.edu/etd/5264.
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Populations of the introduced book trout, Salvelinus fontinalis, have recently become more widespread and abundant in western North American streams, possible at the expense of native Colorado River cutthroat trout, Oncorhynchus clarki pleuriticus. We examined the intensity and potential mechanism of competition between these species.
Feeding experiments in laboratory stream channels showed that cutthroat trout feeding efficiency decreases in the presence of a brook trout. Decreased feeding efficiency appeared to be due to interference, as cutthroat trout were inactive in the presence of the brook trout. Evidence for interference competition in the feeding experiments was also given by the fact that brook trout feeding efficiency was lower than the feeding efficiency of cutthroat trout. The decreased feeding efficiency of cutthroat trout in the presence of brook trout was due to decreased attack rates by cutthroat trout, and was not due to attacks and consumption of the food items by the brook trout.
A field enclosure experiment, in which riffle-pool sections of a stream were isolated by fencing, was performed to determine if the presence of brook trout had a negative effect on the growth, fat content, and diet of cutthroat trout. Cutthroat trout fat levels were significantly lower in the presence of brook trout. The growth of cutthroat trout was not significantly different in the presence and absence of brook trout, but there was a trend fro lower growth of cutthroat trout in the presence of brook trout. Diet choices and total biomass of prey consumed by cutthroat trout in the field experiment and in a survey of three streams were not affected by the presence of brook trout.
The observed decreased feeding efficiency of cutthroat trout in the presence of brook trout may be the mechanism responsible for the significant;y decreased fat levels during the relatively short, summer growing season and may result in reduced population sizes due to high overwinter mortality and delayed sexual maturity.
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Pohl, Angelika [Verfasser], and Niels [Akademischer Betreuer] Dingemanse. "An analysis of competitive traits in pest ant species / Angelika Pohl ; Betreuer: Niels Dingemanse." München : Universitätsbibliothek der Ludwig-Maximilians-Universität, 2019. http://d-nb.info/1198111844/34.
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Schwartz, Lauren Michele. "The competitive response of Panicum virgatum cultivars to non-native invasive species in southern Illinois." OpenSIUC, 2011. https://opensiuc.lib.siu.edu/theses/765.
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Historically, the tallgrass prairie (TGP) was the largest ecosystem in North America, but today only about 10-15% of the original extent exists today. Some areas have experienced more extreme loss, for example in the state of Illinois less than 0.01% of high-quality native tallgrass prairie remains. Non-native invasive species are a recent phenomenon that threatens the integrity of surviving TGP communities. Ecotypes of dominant C4 grasses are the basis of numerous cultivars, many of which are utilized in prairie restorations. In this study, the effects of three invasive species (Bromus inermis, Schedonorus phoenix, and Poa pratensis) on two lowland (`Alamo' and `Kanlow') and three upland (`Blackwell', `Cave in Rock', and `Trailblazer') cultivars of the dominant C4 grass Panicum virgatum were tested. Two simple pair-wise greenhouse experiments were established in which cultivars were sown as a monoculture or as a mixture of the cultivars with one of three invasive species. Pots were subjected to one of two water treatments with three replicates of each treatment combination. Response variables (height, number of leaves, tiller density, and biomass) and resources (soil moisture, soil pH, soil electrical conductivity, and light intensity) were measured. The greenhouse studies showed that response variables were affected by the presence of invasive species and that the time of growth affected resource levels. Resources are allocated to different areas (i.e growth and reproduction) when competition and stress are implemented on the dominant species. This study was the first to experimentally test for the presence of the physiological stress marker, trigonelline, in a prairie grass. Trigonelline was highest in upland cultivars under low moisture and highest in lowland cultivars under low moisture treatments. The results of these greenhouse studies suggest that invasive species may differentially affect cultivars of Panicum virgatum that may be sown in a prairie restoration. Performance of the P. virgatum cultivars was dependent on the timing of growth, the pot size, the invasive species, as well as soil moisture level. Therefore, when choosing a cultivar source for restoration, resources (i.e. soil moisture) should be looked into to maximize the output of the cultivar.
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Nielsen, Kristin Norma Astrid Toftgaard. "Predicting competitive ability from plant traits: A comparative study of 63 terrestrial herbaceous plant species." Thesis, University of Ottawa (Canada), 1995. http://hdl.handle.net/10393/10227.
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There is critical need for studies on interspecific competition which enable general principles to be deduced that apply beyond the species and conditions of a particular study or site. Studies on plant traits are a key part of this search for general principles. I measured relative competitive ability in 63 terrestrial herbaceous plant species using the phytometer Trichostema brachiatum, to test whether competitive ability can be predicted from simple measurable plant traits. The test species utilised in this experiment represented a wide array of terrestrial vegetation types (e.g. rock. barrens, alvars, old fields), and an array of growth forms, from small rosette species (e.g. Saxifraga virginiensis) to large clonal graminoids (e.g. Agropyron repens). The experiment was carried out under both a "normal" and a "drought" treatment. Multiple linear regression showed that there was a strong relationship between plant traits and competitive ability (Normal treatment--r$\sp2$ = 0.54; Drought--treatment r$\sp2$ = 0.55). Total plant biomass explained 34% of the variation in competitive ability in the normal treatment and below-ground biomass explained 35% of the variation in the drought treatment. Leaf shape explained most of the residual variation. The competitive hierarchy for plants in the normal and drought treatment was compared. Rankings for individual species varied between treatments, however, when all species were compared simultaneously, competitive hierarchies in both treatments were highly correlated (r$\sb{\rm s}$ = 0.91). This suggests that invariant and variant views of competitive hierarchies are not mutually exclusive but instead depend on the scale at which competition is being addressed. On the broad scale, relative competitive abilities appear consistent across different environments. Thus, both traits and hierarchies show general repeatable patterns that allow us to generalize from one set of circumstances to another.
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Kiger, Sarah. "Competitive ability of native and non-native prairie species in response to soil nitrogen and density." Connect to resource, 2006. http://hdl.handle.net/1811/6621.
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Thesis (Honors)--Ohio State University, 2006.<br>Title from first page of PDF file. Document formatted into pages: contains 21 p.; also includes graphics. Includes bibliographical references (p. 12-13). Available online via Ohio State University's Knowledge Bank.
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Long, Michael A. "Tree species composition and oak competitive status in upland hardwood stands approaching mid-rotation in southern Illinois /." Available to subscribers only, 2007. http://proquest.umi.com/pqdweb?did=1404346481&sid=1&Fmt=2&clientId=1509&RQT=309&VName=PQD.
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Mkango, Sara. "Multi-species models of Antarctic krill predators : do competitive effects influence estimates of pre-exploitation whale abundance and recovery?" Master's thesis, University of Cape Town, 2008. http://hdl.handle.net/11427/4911.
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Includes abstract.
Includes bibliographical references (leaves 92-111).<br>Many species of baleen whales and seals in the Southern Hemisphere were subject to intensive overexploitation by commercial harvesting in the last two centuries, and many populations were reduced to very low levels. Krill is the dominant prey item of these species. Harvesting (to near extinction) of the large baleen whales (blue, humpback and fin whales) from the start of the 20th century led to a likely increase in the availability of krill to other krill predators such as the Antarctic minke whales and crabeater seals. This phenomenon is referred to as the “krill surplus” hypothesis and has been a central hypothesis of Antarctic ecosystem studies. This thesis aims to better understand species interactions in the Antarctic through developing and extending multispecies models of the system. The study considered only Region A (IWC Management Areas II, III and IV, 60°W to 130°E) because the numbers of baleen whales harvested in Atlantic/Indian Oceans were far greater than in other Oceans, so that the impacts on the dynamics of these species are likely greater. The simple models of competition between blue and fin whales developed give qualitatively similar results to the Mori-Butterworth Antarctic ecosystem model of an initial number of fin whales before exploitation began that is much lower than single species models suggest. However, there are important features of blue and fin whale CPUE data off Durban over the middle decades of the last century that are not reflected by the model results, and a number of possible reasons for this are advanced. In particular, the introduction of competition in the models predicts a steady fin whale population until 1950, but cannot reproduce the feature in the CPUE data of an increase from the 1920’s to 1950’s. The study then extends the Mori-Butterworth Antarctic ecosystem model by adding squid, which has fast dynamics compared to whales and seals. The model estimates population trends in terms of numbers or biomass. This study indicates that results are particularly sensitive to the density dependence assumed for natural mortality and/or birth rate. The results highlight that the squid biomass trajectory is relatively insensitive to initial squid abundance but depends strongly on the density dependence assumed for squid. Generally, the estimated historical trajectories suggest that the inclusion of squid in the model hardly impacts the maxima reached by other species that benefited from the krill surplus. The model predicts that squid started to increase at about the same time (1920) that the reduction of large baleen whales (blue, humpback and fin whales) commenced under heavy harvesting. This suggests that species with fast dynamics such as squid were possibly the first to benefit from krill surplus, even before minke whales and crabeater seals, which started to increase only about a decade later. The study provides a potential framework for understanding the interplay between species with slow and fast dynamics.
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Poland, Therese M. "Competitive interactions between the spruce beetle, Dendroctonus rufipennis, Kirby, and two secondary species, Ips tridens, Mannerheim, and Dryocoetes affaber, Mannerheim, (Coleoptera: Scolytidae)." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk3/ftp04/nq24341.pdf.
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VERSACE, Soraya. "Influence of climatic variations and competitive interactions on the productivity of mountain forests in Italy." Doctoral thesis, Università degli studi del Molise, 2020. http://hdl.handle.net/11695/97766.
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La crescita degli alberi è influenzata da molteplici fattori tra cui, il clima e i processi di competizione. I cambiamenti climatici hanno un forte impatto sulla crescita degli alberi e possono causare impatti negativi sulle foreste, soprattutto nel bacino del Mediterraneo. Tuttavia, la crescita degli alberi è influenzata anche dalle interazioni competitive. Per quantificare le interazioni competitive tra gli alberi vengono utilizzati indici di competizione, che normalmente sono calcolati su aree di piccole dimensioni. Prevedere le interazioni competitive su aree più estese può essere molto importante e i dati lidar (light detection and ranging) potrebbero essere lo strumento adatto. Sulla base di tali considerazioni, l’obiettivo principale della tesi è stato quello di individuare l’influenza delle variazioni climatiche e delle interazioni competitive sulla crescita di tre importanti specie forestali, faggio (Fagus sylvatica L.), abete rosso (Picea abies L.) e abete bianco (Abies alba Mill.). Il lavoro è strutturato in tre capitoli. Nel primo viene analizzata l’influenza del clima e degli eventi estremi sulla crescita del faggio e dell’abete bianco in plot misti e puri lungo un gradiente latitudinale in Italia. Nel secondo capitolo vengono analizzate le interazioni competitive in popolamenti misti e puri di faggio e abete bianco, situati ai limiti del loro areale di distribuzione (Italia meridionale). Nel terzo capitolo, invece, sono state stimate le dinamiche di competizione di abete bianco e abete rosso, situati nel comune di Lavarone (Trentino), e individuata la relazione tra le interazioni competitive e la biomassa degli alberi. Nel complesso, i risultati hanno evidenziato le risposte di accrescimento degli alberi alle variazioni climatiche e ai processi di competizione in foreste montane in Italia. In particolare, il primo lavoro ha evidenziato una risposta diversa solo a livello regionale per le temperature massime. In Trentino le temperature invernali, per l’abete bianco, ed estive, per entrambe le specie, hanno avuto un minor impatto negativo sulla crescita radiale degli alberi rispetto ai siti meridionali. Nonostante ciò, i risultati ottenuti dalle correlazioni (crescita radiale-indici di siccità) e dall’analisi delle componenti principali hanno evidenziato che nessun popolamento era sensibile alla siccità estiva. Nel secondo lavoro è stato osservato come l'incremento dell'area basimetrica, sotto l'influenza negativa di alti livelli di competizione e alta pendenza del terreno, variava tra i popolamenti. In tal senso sono state osservate interazioni competitive più elevate in Molise rispetto alla Calabria. Infine, nel terzo lavoro, è stato dimostrato che le metriche lidar possono essere utilizzate per prevedere gli indici di competizione. Inoltre, è stato osservato che la biomassa diminuiva all'aumentare della competizione. I risultati dei tre lavori hanno evidenziato che per la scelta di opzioni forestali sostenibili è necessario considerare le condizioni del sito in cui tali specie si trovano e la struttura dei popolamenti forestali, in termini di densità e disposizione degli alberi. Inoltre, è stato constatato che l’utilizzo di tecniche di telerilevamento (es. lidar) possono essere molto utili in campo forestale, poiché possono fornire informazioni su aree più estese.<br>Tree growth is influenced by multiple factors including, climate and competition processes. Climate change has a strong impact on growth of trees and can cause negative impacts on forests, especially in the Mediterranean basin.
However, tree growth can also be influenced by competitive interactions, through the use and absorption of resources within tree communities. To quantify the level of competition between trees, competition indices are used, which are normally computed over small areas. Predicting competitive interactions over larger areas can be very important and light detection and ranging (lidar) data, could be the suitable tool. Based on these considerations, the main objective of the thesis was to identify and study the influence of climatic variations and competitive interactions on the growth of three important forest species, European beech (Fagus sylvatica L.), Norway spruce (Picea abies L.) and silver fir (Abies alba Mill.). The work is structured into three chapters, in which the first analyzes the influence of climate and extreme events on the radial growth of beech and silver fir in mixed and pure plots along a latitudinal gradient in Italy. In the second chapter the competitive interactions in mixed and pure populations of European beech and silver fir, located at the limits of their distribution range (southern Italy) are analyzed. In the third chapter, instead, was to estimate the competition dynamics for individual trees of Norway spruce and silver fir, located in the municipality of Lavarone (Trentino), and to identify the relationship between competitive interactions and tree aboveground biomass. Overall, results highlighted the response of trees under to climate and competition processes in mountain forests in Italy. In particular, the results of the first work showed a different response only at the regional level for the maximum temperatures. In Trentino the temperatures in winter, for silver fir, and summer, for both species, had a lesser negative impact on radial growth of trees compared to southern sites. Despite this, the results obtained from the correlations (radial growth-drought indices) and from principal component analysis have shown that no plot was sensitive to summer drought. Results are important to implement operational techniques that increase species adaptation to climate change. In the second work showed that the basal area increment, under the negative influence of high competition levels and slope terrains, varied between stands. In this sense, higher competitive interactions have been observed in Molise than in Calabria. Finally, in the third work showed that lidar metrics could be used to predict the competition indices of individual trees. In addition, biomass was observed to decrease as competition increased. The results of the three works showed that for the choice of sustainable forestry options it is necessary to consider the conditions of the site where these species are found and the structure of the forest stands, in terms of density and arrangement of the trees. Furthermore, it has been found that the use of remote sensing techniques (e.g. lidar) can be very useful in the forestry field, since they can provide information on larger areas.
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Winslow, Christopher J. "Competitive interactions between young-of-the-year smallmouth bass (Micropterus Dolomieu) and round goby (Apollonia melanostomus)." Bowling Green State University / OhioLINK, 2010. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1288625667.
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Walker, Emer Ann [Verfasser], Johannes [Akademischer Betreuer] Kollmann, and Karl F. [Akademischer Betreuer] Auerswald. "It’s a matter of source: The competitive effects of dominant species on calcareous grassland forbs / Emer Ann Walker. Gutachter: Johannes Kollmann ; Karl F. Auerswald. Betreuer: Johannes Kollmann." München : Universitätsbibliothek der TU München, 2014. http://d-nb.info/1064075509/34.
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Officer, Andrew Russell. "Powdery Mildew (Erysiphe cruciferarum) Affects the Allelopathic and Competitive Abilities of Invasive Garlic Mustard (Alliaria petiolata)." Wright State University / OhioLINK, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=wright1363272398.
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Laube, Julia Verfasser], Annette [Akademischer Betreuer] Menzel, Tim H. [Akademischer Betreuer] Sparks, and Susanne S. [Akademischer Betreuer] [Renner. "Performance of native and invasive plant species under climate change – phenology, competitive ability and stress tolerance / Julia Laube. Gutachter: Annette Menzel ; Tim H. Sparks ; Susanne S. Renner. Betreuer: Annette Menzel." München : Universitätsbibliothek der TU München, 2015. http://d-nb.info/1075317274/34.
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Wendelberger, Kristie Susan. "Evaluating plant community response to sea level rise and anthropogenic drying: Can life stage and competitive ability be used as indicators in guiding conservation actions?" FIU Digital Commons, 2016. http://digitalcommons.fiu.edu/etd/2558.
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Increasing sea levels and anthropogenic disturbances have caused the world’s coastal vegetation to decline 25-50% in the past 50 years. Future sea level rise (SLR) rates are expected to increase, further threatening coastal habitats. In combination with SLR, the Everglades ecosystem has undergone large-scale drainage and restoration changing Florida’s coastal vegetation. Everglades National Park (ENP) has 21 coastal plant species threatened by SLR. My dissertation focuses on three aspects of coastal plant community change related to SLR and dehydration. 1) I assessed the extent and direction coastal communities—three harboring rare plant species—shifted from 1978 to 2011. I created a classified vegetation map and compared it to a 1978 map. I hypothesized coastal communities transitioned from less salt- and inundation-tolerant to more salt- and inundation-tolerant communities. I found communities shifted as hypothesized, suggesting the site became saltier and wetter. Additionally, all three communities harboring rare plants shrunk in size. 2) I evaluated invading halophyte (salt-tolerant) plant influence on soil salinity via a replacement series greenhouse experiment. I used two halophytes and two glycophytes (non-salt-tolerant) to look at soil salinity over time under 26 and 38‰ groundwater. I hypothesized that halophytes increase soil salinity as compared to glycophytes through continued transpiration during dry, highly saline periods. My results supported halophytic influence on soil salinity; however, not from higher transpiration rates. Osmotic or ionic stress likely decreased glycophytic biomass resulting in less overall plant transpiration. 3) I assessed the best plant life-stage to use for on-the-ground plot-based community change monitoring. I tested the effects of increasing salinity (0, 5, 15, 30, and 45‰) on seed germination and seedling establishment of five coastal species, and compared my results to salinity effects on one-year olds and adults of the same species. I hypothesized that seedling establishment was the most vulnerable life-stage to salt stress. The results supported my hypothesis; seedling establishment is the life-stage best monitored for community change. Additionally, I determined the federally endangered plant Chromolaena frustrata’s salinity tolerance. The species was sensitive to salinity >5‰ at all developmental stages suggesting C. frustrata is highly threatened by SLR.
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Park-Dwyer, Sarah Evelyn. "Modelling competition in two-species mixtures." Thesis, University of East Anglia, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.323340.
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Janse, Van Vuuren Adriaan. "Niche Occupation in Biological Species Competition." Thesis, Stellenbosch : University of Stellenbosch, 2008. http://hdl.handle.net/10019.1/2932.
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Thesis (MSc (Logistics))--University of Stellenbosch, 2008.<br>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.
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Janse, van Vuuren Adriaan. "Niche occupation in biological species competition /." Link to the online version, 2008. http://hdl.handle.net/10019/753.
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Celiker, Hasan. "Competition between species can drive public-goods cooperation within a species." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/70790.
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Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2012.<br>Cataloged from PDF version of thesis.<br>Includes bibliographical references (p. 40-43).<br>Costly cooperative strategies are vulnerable to exploitation by cheats. Microbial studies have suggested that cooperation can be maintained in nature by mechanisms such as reciprocity, spatial structure and multi-level selection. So far, however, almost all laboratory experiments aimed at understanding cooperation have relied on studying a single species in isolation. In contrast, species in the wild live within complex communities where they interact with other species. Little effort has focused on understanding the effect of interspecies competition on the evolution of cooperation within a species. We test this relationship by using sucrose metabolism of budding yeast as a model cooperative system. We find that when co-cultured with a bacterial competitor, yeast populations become more cooperative compared to isolated populations. We show that this increase in cooperation within yeast is mainly driven by resource competition imposed by the bacterial competitor. A similar increase in cooperation is observed i<br>by Hasan Celiker.<br>S.M.
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Carlsson, Linnéa. "Stable Coexistence of Three Species in Competition." Thesis, Linköping University, Department of Mathematics, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-18807.
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<p>This report consider a system describing three competing species with populations <em>x</em>, <em>y</em> and <em>z</em>. Sufficient conditions for every positive equilibrium to be asymptotically stable have been found. First it is shown that conditions on the pairwise competitive interaction between the populations are needed. Actually, these conditions are equivalent to asymptotic stability for any two-dimensional competing system of the three species. It is also shown that these alone are not enough, and that a condition on the competitive interaction between all three populations is also needed. If all conditions are fulfilled, each population will survive on a long-term basis and there will be a stable coexistence.</p>
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Rasheed, Shaker M. "A reaction-diffusion model for inter-species competition and intra-species cooperation." Thesis, University of Nottingham, 2013. http://eprints.nottingham.ac.uk/13545/.
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This thesis deals with a two component reaction-diffusion system (RDS) for competing and cooperating species. We have analyse in detail the stability and bifurcation structure of equilibrium solutions of this system, a natural extension of the Lotka-Volterra system. We find seven topologically different regions separated by bifurcation boundaries depending on the number and stability of equilibrium solutions, with four regions in which the solutions are similar to those in the Lotka-Volterra system. We study RDS in the small parameter of the range $0< \lambda \ll 1 $ (fast diffusion and slow reaction), and in a few cases we assume $\lambda=O(1)$. We consider three types of initial conditions, and we find three types of travelling wave solutions using numerical and asymptotic methods. However, neither numerical nor asymptotic methods were able to find a particular travelling wave solution which connects a coexistence state say, $(u_0,w_0)$ to an extinction state $(0,0)$ when $0< \lambda \ll 1 $. This type can be found when the reaction-diffusion system satisfy the symmetry property and $\lambda=1$.
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Nguyen, Tung Shen Wenxian Hetzer Georg. "A-stability for two species competition diffusion systems." Auburn, Ala., 2006. http://repo.lib.auburn.edu/2006%20Summer/Dissertations/NGUYEN_TUNG_28.pdf.
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Fisher, E. M. "Competition for food in the Bryozoa." Thesis, University of Liverpool, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.279719.
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Idjadi, Joshua Aziz. "Aggregation promotes species coexistence among reef-building corals." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 96 p, 2008. http://proquest.umi.com/pqdweb?did=1609283431&sid=6&Fmt=2&clientId=8331&RQT=309&VName=PQD.
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Van, der Hoff Q., JC Greeff, and TH Fay. "Defining a stability boundary for three species competition models." Elsevier, 2008. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1001763.
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a b s t r a c t
A periodic steady state is a familiar phenomenon in many areas of theoretical biology and provides a
satisfying explanation for those animal communities in which populations are observed to oscillate in a
reproducible periodic manner. In this paper we explore models of three competing species described by
symmetric and asymmetric May–Leonard models, and specifically investigate criteria for the existence
of periodic steady states for an adapted May–Leonard model:
x˙ = r(1 − x − ˛y − ˇz)x
y˙ = (1 − ˇx − y − ˛z)y
z˙ = (1 − ˛x − ˇy − z)z.
Using the Routh–Hurwitz conditions, six inequalities that ensure the stability of the system are
identified. These inequalities are solved simultaneously, using numerical methods in order to generate
three-dimensional phase portraits to illustrate the steady states. Then the “stability boundary” is
defined as the almost linear boundary between stability and instability. All the mathematics discussed
is suitable for advanced undergraduate mathematics or applied mathematics students, offering them
the opportunity to incorporate a computer algebra system such as Mathematica, DERIVE or Matlab in
their investigations. The adapted May–Leonard model provides a practical application of steady states,
stability and possible limit cycles of a nonlinear system.
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Flower, Tom P. (Thomas Patrick). "Competition for food in meerkats (Suricata suricatta)." Diss., University of Pretoria, 2009. http://hdl.handle.net/2263/25367.
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In group living species animals commonly compete for limited resources such as food (Darwin 1859). Winning competition for food may be beneficial for an individuals survival or reproductive success (Williams 1966; Clutton-Brock 1988; Metcalfe et al 1995) but conflict with group members may be costly as it typically involves aggression (Huntingford&Turner 1987, Mesterton-Gibbons&Adams 1998). Asymmetries between individuals are predicted to determine the outcome of competition (Maynard-Smith&Parker 1976), and individuals are expected to steal food when the benefit to them is greatest (Barnard 1984; Trivers 1972). I therefore investigate what determines the outcome of competition for food between group members, and what factors affect whether group members try to steal food in the cooperatively breeding meerkat (Suricatta suricatta). Meerkats competed for food items infrequently and the owner of a food item typically won competition, but dominant individuals and breeding females were more likely to win competition than other group members. This provides support for models of conflict over resources in group living species which predict that ownership may determine the outcome of competition, thereby avoiding frequent costly conflict (Maynard-Smith 1982). Furthermore, where large asymmetries exist between contestants in dominance status or the value of a resource, these may determine the outcome of competition (Maynard-Smith&Parker 1976; Grafen 1987). Meerkats varied in how frequently they tried to steal food depending upon the costs and benefits of competition. Dominant individuals competed for food more frequently which is likely to reflect reduced costs of competition as subordinate individuals may avoid conflict with them (Packer&Pusey 1985). Females competed for food more frequently than males and more frequently during breeding, reflecting the higher costs of reproduction to females compared to males (Williams 1966; Trivers 1972). Meerkats compete more frequently for food when food availability is low, which indicates that food items may be more valuable when they are rare. Meerkats in smaller groups competed more frequently. In cooperatively breeding species group members undertake a large number of costly helping behaviours. Individuals in small groups each contribute more effort to helping than individuals in large groups and suffer higher costs which may increase the benefit of food to them (Clutton-Brock et al 1998a; Clutton-Brock et al 2001a). Competition for the opportunity to breed in cooperatively breeding meerkats has resulted in despotic dominance hierarchies where a dominant female monopolises breeding and reproductively suppresses subordinates (Clutton-Brock et al 2001b). Dominant females stole more food than any other group members. This is likely to be a consequence of the high costs of reproduction for the dominant breeding female in species with high reproductive skew (Creel&Creel 1991; Clutton-Brock et al 2001b). Furthermore, dominant females were more aggressive and more successful in competition for food with their reproductive competitors. Dominant females may therefore use competition for food as a means of asserting dominance over their reproductive competitors which could contribute to reproductive suppression (Creel et al 1992; Williams 2004; Kutsukake&Clutton-Brock 2006b; Young et al 2006).<br>Dissertation (MSc)--University of Pretoria, 2011.<br>Zoology and Entomology<br>unrestricted
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Fay, TH, and JC Greeff. "A three species competition model as a decision support tool." Elsevier, 2007. http://encore.tut.ac.za/iii/cpro/DigitalItemViewPage.external?sp=1000167.
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An overcrowding problem of nyala, and lately also of impala in the Ndumo Game Reserve,
South Africa, has been detrimental to other species and vegetation structures over a period
of two decades. In the present study a deterministic model for three competing species
(where two species tend to be overpopulated while the third faces probable localized extinction)
is constructed, while future trends coupled with their coexistence are projected.
On a mathematical basis, we seek reasons for the failure of the cropping strategies
implemented by management over the last two decades, and suggest alternative,
scientifical-based approaches to the calculation of cropping quotas to ensure the future
coexistence of all three species. A system of three first-order nonlinear differential equations
is used, with parameter values based on field data and opinions of specialist ecologists.
The effect of various cropping strategies, and the introduction of a fourth species (man as a
predator) to the system, is investigated mathematically. This model was implemented as a
harvesting strategy in 2002, and is being continuously tested. Final assessment can only be
done over a 10–15-year period, but so far indications are promising.
31
Bezuglyy, Andriy. "Reaction-diffusion-advection models for single and multiple species." The Ohio State University, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=osu1253646281.
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Minor, Rebecca. "Competition for Conifer Cones as a Potential Mechanism of Endangerment for the Mount Graham Red Squirrel." Thesis, The University of Arizona, 2010. http://hdl.handle.net/10150/193441.
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Non-native species are a major cause of endangerment for native species, but the mechanisms are often unclear. As species invasions continue to rise, it is important to understand how to mitigate this threat. Our field experiment quantified the impact of introduced Abert's squirrels (Sciurus aberti) on rates of food removal within the range of the critically endangered Mount Graham red squirrel (Tamiasciurus hudsonicus grahamensis). In the presence of Abert's squirrels, the time until 50% of cones were removed was 5.55 days faster than when Abert's squirrels were excluded (95% confidence interval 2.25 to 11.63 days). The impact on food availability as a result of cone removal by Abert's squirrels suggests the potential of food competition as a mechanism of endangerment for the Mount Graham red squirrel. Eradication of established non-native populations is rare. Management targeted at specific mechanisms by which non-natives cause endangerment is an essential tool for conservation.
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Tillett, David McIlvain. "Lipid productivity and species competition in laboratory models of algal mass cultures." Diss., Georgia Institute of Technology, 1988. http://hdl.handle.net/1853/10274.
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Mills, Catherine. "Competition between specialist and generalist species in computational and experimental model ecosystems." Thesis, University of Edinburgh, 2017. http://hdl.handle.net/1842/25502.
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An ecological community is complex and the mechanisms behind the assembly of such a community are still poorly understood. Here, we concentrate on the question of what mechanisms affect the proportion of specialists and the proportion of generalists in a community. First, we use an individual-based model to explore the effects of the available resource spectrum on the specialist-generalist balance in well-mixed and spatially structured environments. In the well-mixed model, we uncover a new mechanism which we term `resource spectrum engineering', in which opportunistic specialists occupying small niches in a mostly generalist community can change the resource spectrum that is experienced by other species strongly disfavouring generalists and causing a community-wide shift towards specialist strategies. Extending to a spatially structured model in which the dispersal distance of species may be limited, we find that specialism is linked to intermediate dispersal lengths, whereas generalism is linked to short and long dispersal lengths. We then investigate two real microbial systems, using 16rRNS sequence data. In the first experiment, we identify functional groups of specialists and generalists by perturbing the microbial environment with variable nutrient concentrations and establishing which groups survive across different concentrations and which do not. In the second experiment we use many replicates of samples from the same source to find co-occur find that generalist species may be more likely to be dependant on the presence of each other than on specific environmental conditions.
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Derbridge, Jonathan, and Jonathan Derbridge. "Ecology and Conservation of Endangered Territorial Species Under Invasion." Diss., The University of Arizona, 2018. http://hdl.handle.net/10150/626655.
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Biological invasions threaten biodiversity globally, and degraded ecosystems increase the potential for invaders to compete with threatened native populations. In natural systems, niche partitioning minimizes interspecific competition, but introduced species may alter expected outcomes by competing with ecologically similar species for scarce resources. Where food production is highly variable, coexistence of native and invasive competitors may depend on dietary niche flexibility. Territorial species under invasion face additional challenges to maintain economically defendable territories. From 2011-2016, we conducted removal and behavior experiments to determine effects of non-territorial introduced Abert’s squirrels (Sciurus aberti) on diet, space use, and territoriality of endangered Mount Graham red squirrels (MGRS; Tamiasciurus fremonti grahamensis) in their declining habitat in the Pinaleño Mountains, Arizona. We collected comparative data from Arizona sites of natural syntopy between Abert’s and Fremont’s squirrels (T. fremonti). Stable isotope analysis revealed similar dietary partitioning among populations. Experimental removals did not appear to affect MGRS diet. Space use by MGRS responded inconsistently to removals; territory sizes increased after the first removal, but did not change following the second removal. Territory sizes and body mass of MGRS were sensitive to conspecific population density and food production. Behavioral experiments showed MGRS were more aggressive than other Fremont’s squirrels (hereafter, red squirrels). Dietary flexibility of Abert’s squirrels may have facilitated coexistence with MGRS, possibly due to coevolved resource partitioning with red squirrels. However, aggressive territoriality toward Abert’s squirrels may incur fitness costs for MGRS especially during poor food production years. Climate change may reduce the advantage of ecological specialist species globally, and where introduced species are better-adapted to novel environmental conditions, native species may ultimately be replaced.
36
Abdollahian-Noghabi, Mohammad. "Ecophysiology of sugar beet cultivars and weed species subjected to water deficiency stress." Thesis, University of Reading, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.299308.
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Buyukates, Yesim. "Characterization of the plankton community in the lower Rincon Delta: Investigations regarding new approaches to management." Diss., Texas A&M University, 2003. http://hdl.handle.net/1969.1/1312.
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In light of increasing harmful algal blooms and the need to protect human health and aquatic resources, proactive management approaches merit further study. For this purpose I conducted field samplings to characterize plankton community composition and laboratory experiments to test some approaches to new management schemes in the lower Rincon Delta. On site measurements and microscopic analysis showed that environmental parameters and plankton community composition varied considerably among sampling stations and sampling dates. A recent modeling study suggested that manipulation of freshwater inflow to estuaries might prevent phytoplankton blooms and enhance secondary productivity. To test this theory I conducted three semi-continuous design and flow-through incubation design experiments using natural plankton assemblages. I investigated the effect of two different pulsing regimes of inflow and nutrient loading on zooplankton densities, and phytoplankton biomass and diversity. Despite differences in zooplankton structure and phytoplankton community composition between the two experiment designs, the results confirmed that pulsed inflows might alter plankton dynamics. My findings showed that 3-day pulse treatments consistently supported greater zooplankton densities and higher phytoplankton species diversity when compared to 1-day pulse treatments. In addition, accumulation of phytoplankton biovolume remained low during 3-day pulse treatments. Differences in zooplankton performance between 3-day pulse and 1-day pulse inflow treatments were likely due to the ability of phytoplankton to uptake and store greater amounts of nutrients under conditions of 3-day pulse inflow. This resulted in food of higher quality for zooplankton, and might have supported greater zooplankton population growth rates. Additionally, in an attempt to understand the mechanisms leading to high biodiversity in aquatic ecosystems, I built a resource-storage model and studied the effects of resource-storage on competition of multiple phytoplankton species on multiple abiotic resources. I compared this model with a well-established multi-species competition model. My results showed that for certain species combinations a resource-storage-based model can generate dissimilar outcomes when compared to a model without resource-storage.
38
Alvarez, Aguirre Maria Guadalupe. "Effects of interspecific competition and herbivory on an exotic species, Senecio inaequidens DC." Thesis, Imperial College London, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.498646.
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Harrison, Emma Clare. "The Pararge species of Madeira : an examination of the role of interspecific competition." Thesis, Manchester Metropolitan University, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.343456.
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Bliss, Kristin Mays. "Impact of nutrient heterogeneity on plant response and competition in Coastal plain species." Diss., Virginia Tech, 2001. http://hdl.handle.net/10919/29755.
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Relationships between nutrient heterogeneity, root foraging behavior and short-term competitive interactions were investigated for six species native to southeastern USA. Monoculture, two- and six-species garden plots were established and fertilized to create spatially homogeneous or heterogeneous nutrient conditions. After 3.5 months, root proliferation in rich patches (precision) and aboveground biomass response to heterogeneity were assessed in monocultures, and competitive outcomes (aboveground biomass) were determined from mixed-species plots. In monoculture plots, two species were relatively precise foragers, but no species showed significant aboveground biomass response to nutrient treatment. Correlations between precision and aboveground biomass were weak (-0.40 < r < 0.17). In two-species plots, interspecific competition was influenced by soil heterogeneity in two of six cases tested (P < 0.05), and precision was the behavior most correlated with competitive success. In six-species plots, spatial pattern of nutrients had no influence on aboveground growth or competition. Results suggest that heterogeneity influences competition, but the influence is context-specific and generally small. Precision may be the foraging behavior that most influences interspecific interactions.<br>Ph. D.
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Averill, Isabel E. "The Effect of Intermediate Advection on Two Competing Species." The Ohio State University, 2012. http://rave.ohiolink.edu/etdc/view?acc_num=osu1324056383.
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Costa, Zacharia. "SPECIES LEVEL DIFFERENCES IN THE ECOLOGY OF TWO NEOTROPICAL TADPOLE SPECIES: RESPONSES TO NONLETHAL PREDATORS AND THE ROLES OF COMPETITION AND RESOURCE USE." VCU Scholars Compass, 2011. http://scholarscompass.vcu.edu/etd/2635.
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Closely related species at the same trophic level are often considered to be ecologically equivalent. However, it is clear that individuals species can have unique functional roles that drive community and ecosystem processes. In this study we examine the growth responses of two Neotropical hylid tadpole species, Agalychnis callidryas and Dendropsophus ebraccatus, to intraspecific and interspecific competition. We also look at density-dependent effects of each on phytoplankton, periphyton and zooplankton, as well as their responses to a caged dragonfly predator through ontogeny. Intraspecific competition affected both species similarly, and their effects on resources were qualitatively similar but quantitatively different. Predators affected resource levels and interspecific competition. Predator effects on tadpole size varied in both magnitude and direction through ontogeny for both species. This study shows that closely related species at the same trophic level can have different ecological roles and that tadpoles are more functionally unique than previously thought.
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Brunkalla, Roberta Joann. "Influence of Mixing and Buoyancy on Competition Between Cyanobacteria Species in Upper Klamath Lake." PDXScholar, 2017. https://pdxscholar.library.pdx.edu/open_access_etds/3998.
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Cyanobacterial blooms in lakes impact human health, the economy, and ecosystem health. It is predicted that climate change will promote and increase the frequency and intensity of cyanobacterial blooms due to unique physiological adaptions that allow cyanobacteria to exploit warm stable water bodies. Key cyanobacteria physiological adaptions include nitrogen fixation, buoyancy regulation and higher optimum growth temperatures. The largest uncertainty of predicting the effect of climate change is in understanding how the interactions among species will change. Adding to the ambiguity, cyanobacteria physiological adaptions can vary based on lakespecific ecotypes and can have different sensitivities to temperature. It is critical to understand how cyanobacterial physiological adaptions impact species interactions in order to improve and devise adaptable, short‐term management methods for bloom control. This study investigated how weather patterns and algal buoyancy regulation influence the competition and accumulation of two bloom‐forming buoyant cyanobacteria species (Aphanizomenon flos‐aquae (APFA) and toxin‐forming Microcystis aeruginosa (MSAE)) in Upper Klamath Lake (UKL), Oregon. The focus was confirming the buoyancy rate of the APFA in Upper Klamath Lake and exploring whether short‐term weather conditions could lead to dangerous accumulations of APFA or MSAE. A sensitivity analysis was conducted on the model's buoyancy terms and growth curves to see if the outcome of competition was influenced by these parameters.
UKL specific buoyancy rates were measured on APFA from samples taken directly from the lake in the summer of 2015. Tracking software was used to measure APFA movement through water, and individual colony movement was averaged to obtain a single buoyancy rate. There was a high degree of agreement between the calculated APFA buoyancy rate in UKL (0.89 ± 0.34 m hr-1) with the rate published by Walsby (1995; 0.9 ± 0.5 m hr-1).
This study investigated how weather patterns and buoyancy regulation influenced the outcome of competition between APFA and MSAE. Weather and water column temperature data were collected from UKL in the summer of 2016. A onedimensional hydrodynamic model was used to calculate the lake's thermal and turbulence structure on days with contrasting weather patterns (hot/cool and windy/calm). A competition model was used to calculate the accumulation of APFA and MSAE cells in regular intervals through the water column under the various weather scenarios. MSAE accumulation was significantly influenced by the thermal and turbulence regimes, but APFA maintained high accumulations under every regime and was the better competitor under every thermal and turbulence regime. MSAE was more negatively impacted by high turbulence than low temperatures.
APFA's optimum temperature growth curve was found to be important in determining the outcome of competition between APFA and MSAE. Surprisingly, competition was not sensitive to changes in buoyancy rates. Buoyancy was not found to be a function of algal accumulation under any thermal and turbulence regime.
The impacts of climate change and human‐induced enrichment has the potential to change existing patterns of species interactions in lentic systems. Restoration and management efforts should consider the significance of cascading ecological responses to climate change. Understanding how key physiological adaptions operate is the first step to assessing the scope of this impact. While buoyancy might not play a large role in competition in UKL, it might be possible to use mixing to suppress MSAE because it is negatively impacted by high turbulence. If MSAE hot spots become a reoccurring problem in UKL, lakes managers might be able to use localized mixing to suppress MSAE blooms in these problem areas.
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Forsman, J. (Jukka). "Heterospecific attraction in breeding bird communities:implications to habitat selection and species interactions in a landscape perspective." Doctoral thesis, Oulun yliopisto, 2000. http://urn.fi/urn:isbn:9514256263.
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Abstract
I studied the structure of European breeding forest bird communities on several spatial scales focusing on heterospecific attraction among birds (i.e., the attraction of individuals to the company of interspecifics). Namely, I examined how heterospecific attraction affects habitat selection in migrant birds and the potential role of predation risk in enhancing heterospecific attraction during breeding with particular emphasis regarding the interaction between resident and migrant birds.
Geographically, low densities and low relative proportions of resident titmice (Parus and Aegithalos spp.) were associated with harsh winter conditions. The densities of northern European titmice populations are suggested to be lower than expected on the basis of summer productivity potentially causing geographical variation with respect to the interactions between resident and migrant birds. As expected, the associations between titmice and migrants appear stronger and more positive in northern Europe than elsewhere.
Heterospecific attraction in habitat selection among migrant species was studied both experimentally and theoretically. An increased density of titmice resulted in a higher number and abundance of migrant species than the removal treatment, suggesting that resident birds are used as cues for locating profitable breeding sites. From a theoretical perspective and under most conditions, the use of heterospecific cues proved to be a better habitat selection strategy than selection of sites based on direct assessment of the relative quality of habitat patches. Only when interactions (both positive and negative) between migrants and residents were weak and sampling costs of both strategies were about equivalent, did individuals using direct sampling gain in fitness.
Heterospecific attraction during breeding in relation to predation risk was assessed by examining the spatial distribution of birds. Both experimentally increased perceived predation risk and naturally occurring predation risk created by the presence of sparrowhawk (Accipiter nisus) i.e., relative to the vicinity of nesting hawk, resulted in more clumped distribution of birds than areas of lower risk. Around sparrowhawks nest, however, clumping was apparent for only one forest type and only among study plots including both large (≥ 20 g, preferred prey) and small birds (< 20 g).
To conclude, heterospecific attraction of migrants to resident birds contributes to the structure of local avian communities in forest landscapes. Heterospecific attraction among birds is strengthened by increased predation risk causing variation in species interactions when considered in a landscape perspective.
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Schwartz, Lauren Michele. "A comparative study of the population dynamics of four Amaranthaceae species." OpenSIUC, 2015. https://opensiuc.lib.siu.edu/dissertations/1087.
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Some of the most problematic agricultural weeds found in the Midwest United States are found in the Amaranthaceae family, such as Amaranthus palmeri and A. tuberculatus. These summer annual weeds are troublesome due to their competitive ability, high seed production, and resistance to herbicides from several modes of action which complicates management in field crops and has led to significant yield loss. Achyranthes japonica and Iresine rhizomatosa are two perennial species in the same family as A. palmeri and A. tuberculatus that occur in similar habitats as one another, but differ in invasiveness. Achyranthes japonica is a non-native, invasive species that is becoming a threat to forested areas and has been observed along agricultural field margins. Iresine rhizomatosa also occurs in forest habitats but is an endangered species in Illinois. This research seeks to determine the comparative life history and relative competitiveness of closely related weedy species when challenged with a dominant species. Specifically, select, closely related weedy species in the Amaranthaceae plant family that occur in southern Illinois were compared, i.e., Achyranthes japonica, Amaranthus palmeri, Amaranthus tuberculatus, and Iresine rhizomatosa. The first study examined the life history characteristics of A. japonica in regards to survivorship, growth and fecundity at two sites in southern Illinois (Chapter 2). Achyranthes japonica is a relatively new invasive species that has been poorly studied. This experiment showed that regardless of site, environmental factors had a significant effect on seedling emergence and seed viability, which decreased from 2012 to 2013 during a drought year and rebounded from 2013 to 2014 following flooding. On average, individuals at the driest site had higher performance and fecundity, regardless of year. The second experiment tested the relative competitive effect and response of the Amaranthaceae species to Glycine max, first in a greenhouse study that tested shading and nitrogen resource drawdown for each species, and second in a controlled field experiment that tested intraspecific competition (Chapter 3). In addition, A. japonica seedlings were planted as either unmanipulated seedlings (uncut A. japonica) or as a seedling cut back to the soil surface at the four-node stage (cut A. japonica) at which point seedlings have reached a perennial growth stage. The greenhouse experiment showed that the four species each drew down light significantly, but not nitrogen. Shading decreased the aboveground biomass of the species in comparison to unshaded controls. Supplemental nitrogen, however, increased the aboveground biomass of A. palmeri and A. japonica. The supporting controlled field experiment showed that the competitive response of the weed species to the presence of G. max showed a reduction in height compared to the weed species grown in monocultures. Glycine max and the weed species, except I. rhizomatosa, showed a similar competitive effect and response when aboveground biomass was measured. Achyranthes japonica attained the highest belowground biomass when grown as a monoculture and in the presence of G. max. A competitive effect ranking was determined to be A. palmeri > A. tuberculatus > cut A. japonica = uncut A. japonica = I. rhizomatosa with the competitive response ranking being the inverse. The third study implemented an integral projection model (IPM) to determine the population growth rate of each species and how they compared to one another (Chapter 4). This experiment showed that A. palmeri, A. tuberculatus and A. japonica each had a population growth rate greater than one indicating rapidly growing populations. By contrast, I. rhizomatosa had a population growth rate less than one indicating a declining population. The results suggest that A. japonica has not yet shown the ability to escape management strategies in agricultural fields implemented by farmers, but it is still an aggressive invasive species that farmers and land owners need to be able to identify. This species has many similar characteristics to the Amaranthus species, such as the ability to colonize in areas with limiting resources, continual flushes of germination throughout the growing season, the ability to outcompete other weed species, and high fecundity but, A. japonica also is a perennial species that can withstand removal of shoot material and has a high germination rate. Based on these results, only early detection and rapid response methods should be relied on to keep these species out of areas in and around agricultural fields. Iresine rhizomatosa’s performance in these studies was consistent with its rarity.
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Costa, Sofia Conde. "Antagonistic interactions between dominant invasive and native ant species in citrus orchards." Master's thesis, ISA, 2017. http://hdl.handle.net/10400.5/14836.
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Mestrado em Engenharia Agronómica - Proteção das plantas / Instituto Superior de Agronomia<br>The Argentine ant, Linepithema humile (Mayr) established in the South of Portugal (Algarve), about 120 years ago. Zina et al. (2017) compared the composition of ant communities foraging in tree canopy in citrus orchards among the three ecological subregions of Algarve (Litoral, Barrocal and Serra) and observed that the invasive dominant species L. humile was absent from Serra. In this work, we tested the hypothesis that dominant native ant species, such as Tapinoma nigerrimum (Nylander) and Lasius grandis Forel could prevent the Argentine ant from invading Serra. Laboratory experiments were carried out, using both Petri dish arenas and cages to assess the antagonistic interactions between the Argentine ant and two dominant native species, at the individual and colony level, respectively. Overall, our results support the tested hypothesis. At the individual level, both T. nigerrimum and L. grandis showed higher aggression and survival levels than Argentine ant. At the colony level, the results suggest that both the Argentine ant and T. nigerrimum were able to recruit a relative large number of individuals from the colony when trying to colonise a food resource defended by the competitor species. In our experimental conditions, T. nigerrimum showed to be more efficient than Argentine ant in this type of competition, as it was able to defend a food resource in four out of five times from the attack of the former species, as well as to dominate a resource defended by Argentine ant in four out of five times<br>N/A
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Story, Heather Marie. "Assessing performance and compatibility of three Laricobius species as predators of hemlock woolly adelgid, Adelges tsugae." Thesis, Virginia Tech, 2010. http://hdl.handle.net/10919/42362.
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Predation, egg production and survivorship of Laricobius nigrinus Fender, L. rubidus, LeConte, and L. osakensis Montgomery and Shiyaki (proposed), predators of hemlock woolly adelgid, Adelges tsugae, Annand, were investigated in the laboratory and in the field. In individual assays, L. rubidus oviposited fewer eggs than either L. nigrinus or L. osakensis. In assays containing congeneric or conspecific groups of adult Laricobius, L. osakensis preyed upon the greatest number of ovisacs. When all three species were together, the numbers of ovisacs preyed upon were similar to the mean of all three individual species. Adult predators fed on few eggs and did not exhibit any species preference. The numbers of A. tsugae ovisacs fed upon did not differ significantly by groups of congeneric or conspecific Laricobius larvae. Laricobius adults and larvae had high survival rates throughout all experiments. In the field, predators were enclosed in sleeve cages with both high (> 120 ovisacs) and low (< 90 ovisacs) A. tsugae densities for 1 wk. All branches with caged beetles had significantly greater numbers of ovisacs preyed upon than branches caged without beetles. No differences in predation or egg production were found among the conspecific and congeneric groupings. Predation was uniformly higher at the high prey-density than at the low prey-density. Survivorship among predators did not differ significantly at either prey density. Results from both laboratory and field experiments suggest that these species are able to co-exist and can be in the same location for biological control of A. tsugae.<br>Master of Science in Life Sciences
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Van, Acker Rene C. "Multiple-weed species interference in broadleaved crops : evaluation of yield loss prediction and competition models." Thesis, University of Reading, 1996. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.308562.
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Zarochentseva, O. "Adaptation of methodology calculation relative crowding coefficient for evaluation competition of tree species in polyculture." Thesis, Видавництво СумДУ, 2012. http://essuir.sumdu.edu.ua/handle/123456789/26816.
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Everard, Katherine Anne. "Soil Moisture as a Mediator for Nitrogen Competition : Implications for Species Invasion and Climate Change." Thesis, Imperial College London, 2008. http://hdl.handle.net/10044/1/4651.
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Simple models of competition for one and two resources have been wellinvestigated for both nitrogen and water. Ecosystem models of nitrogen andwater, including their interactions are also well known, but competition andecosystem processes have rarely been considered together. Using a simpleecosystem model of the nitrogen and water cycles including the dependenceof the nitrogen cycle on soil moisture I examine the outcome of competitionfor nitrogen. This model shows that when there are species specific effectson soil moisture, the competitive outcome for nitrogen can be coexistenceor alternative stable states. The last century has seen widespread invasion of Californian grasslands byannual grasses and forbs from the southern Mediterranean region. Both nitrogenand water have been shown to be limiting in this system. The nativeperennial grasses deplete the soil moisture and nitrogen to a lower levelthan the invasive annual grasses, suggesting that natives should be bettercompetitors. Parameterising my model for a Californian grassland systemI show that in fact the invasive annual grasses are the superior competitorfor nitrogen at lower soil moisture when nitrogen competition is mediatedby soil moisture. The competitive outcome at current rainfall levels in Californiais limited to competitive exclusion by the annuals or coexistence. Climate change caused by anthropogenic emissions of CO2 is already affectingcommunities and ecosystems. Global climate models predict changes inboth mean amount and distribution of precipitation. I investigate the effectof changing precipitation distributions on both ecosystem and communityprocesses in nitrogen limited systems. There is wide variation in ecosystemresponse to increased variation in rainfall. The outcome of N competitionwas more predictable, with the best competitor at lower soil moisture beingconsistently favoured with increasing rainfall variability. This might proveanother problem in restoring native grasses in Californian grasslands.