To see the other types of publications on this topic, follow the link: Diversity distribution.
Dissertations / Theses on the topic 'Diversity distribution'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Diversity distribution.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Chen, Youhua. "Microarthropod diversity and distribution in Southwestern Canada." Thesis, University of British Columbia, 2013. http://hdl.handle.net/2429/44051.
Full textAbstract:
Microarthropod diversity patterns were investigated in southwestern British Columbia, Canada. We surveyed soil microarthropods associated with moss carpets on exposed rocky outcrops. Our survey identified 352 morphospecies in 32 sites spanning a 130 km 60 km area. Previous studies have interpreted strong correlations of species composition with environmental factors as evidence of niche limitation, and strong correlations with spatial factors as evidence of dispersal limitation. Here, we examine 18 ecological variables relevant to either spatial location or environmental aspects of ecological processes, and evaluate their influences on the microarthropod community. We tested whether the relative importance of spatial and environmental factors was concordant between various community attributes including composition, abundance and species richness, and between different taxonomic groups of microarthropods (Oribatida, Mesostigmata, Collembola). We used two different methods (distance-based Mantel and raw data-based ordination methods) to show that spatial variables could not explain composition or compositional turnover for most microarthropod groups, except Collembola. Dispersal limitation of Collembola is surprising given the high dispersal ability of this group. Although environmental factors explained a large amount of spatial variance in composition (raw data-based ordination method) for all microarthropod groups, environmental similarity (distance-based Mantel method) was a poor predictor of compositional similarity for Oribatida and Mesostigmata. Total abundance and species richness could also be explained by combinations of environmental factors, particularly those relating to tree cover and soil-relevant microhabitat variables (i.e, water content/mass, total soil mass and particle mass), but total abundance and richness were themselves only weakly correlated across space. The most important environmental influences on microarthropod communities were tree cover and water mass, followed by distance-to-sea. At the same time, there was a lot of unexplained variance in the composition of microarthropod communities (especially for species incidences) which could not be explained by the available ecological variables. As richness hotspots were dispersed across different habitats for different taxonomic groups, we suggested that species interactions might be equally important as environmental filtering and spatial autocorrelation in shaping microarthropod community structure, especially for patterns in species incidence.
2
Wood, Laura R. "Diversity and distribution of amphibians in Luxembourg." Thesis, University of Kent, 2011. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.544084.
Full text
3
Cooper, Fiona Mary Phillips. "Geographic distribution and genetic diversity of black poplar." Thesis, University of Nottingham, 2001. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.246878.
Full text
4
Gifford, Robert James Moncreiff. "Evolutionary inference from endogenous retrovirus distribution and diversity." Thesis, Imperial College London, 2004. http://hdl.handle.net/10044/1/12030.
Full text
5
Baker, Paul. "The distribution and diversity of actinomycetes in soil fractions." Thesis, University of Warwick, 1997. http://wrap.warwick.ac.uk/59518/.
Full textAbstract:
The results presented were concerned with the survival of Streptomyces coelicolor A3(2) (pll673) inoculated into soil microcosms, which were destructively fractionated so that the total propagules and spore counts could be determined in each of the soil fractions. It was found that this microorganism became associated with the smallest soil aggregates at the time of inoculation but with incubation of the soil microcosms the mycelia and spores became attached to the larger soil aggregates. In the sterile soil, the streptomycete growth was much greater than in nonsterile soil, perhaps due to the increased supply of nutrients created by autoclaving the soil, and the lack of competition. Many of the newly formed spores in sterile soil were not attached to the soil aggregates, which may have enabled them to be distributed to new micro sites. When the distribution of indigenous actinomycetes in soil was investigated, it ressembled the distribution of Streptomyces coelicolor in nonsterile soil after the inoculant had been through one life cycle. Actinomycetes were then isolated from each of the soil fractions, as well as the unfractionated soil, and each of these strains were identified to genera, if possible. It was found that many of the micromonosporas and streptosporangia were isolated from the 63-251 μm soil aggregates, probably because this fraction contained low eubacterial and streptomycetes populations caused by the low organic content within this soil fraction. There was a high eubacterial count in the 2-20 μm soil aggregates and although the actinomycetes were outcompeted within this soil fraction, their diversity was greatest within this fraction. This diversity was also reflected by their production of different secondary metabolites. DNA was extracted from each of the isolates and amplified using specifically designed primers for high GC microorganisms. Each of the products were individually run on denaturing gradient gels. It was found that the amplified products from actinomycetes formed bands on the denaturing gels which migrated to 3 positions. Each of these positions corresponded to major groups of actinomycetes of which streptomycetes formed one group. The patterns corresponding to the isolates of each soil fraction would be compared with the amplified products derived from in situ soil DNA extracts. It was found that the results were not comparable but this work is still being investigated.
6
Pascall, David John. "The diversity and distribution of multihost viruses in bumblebees." Thesis, University of Exeter, 2017. http://hdl.handle.net/10871/31597.
Full textAbstract:
The bumblebees (genus Bombus) are an ecologically and economically important group in decline. Their decline is driven by many factors, but parasites are believed to play a role. This thesis examines the factors that influence the diversity and distribution of multihost viruses in bumblebees using molecular and modelling techniques. In Chapter 2, I performed viral discovery to isolate new multihost viruses in bumblebees. I investigated factors that explain prevalence differences between different host species using co-phylogenetic models. I found that related hosts are infected with similar viral assemblages, related viruses infect similar host assemblages and related hosts are on average infected with related viruses. Chapter 3 investigated the ecology of four of the novel viruses in greater detail. I applied a multivariate probit regression to investigate the abiotic factors that may drive infection. I found that precipitation may have a positive or negative effect depending on the virus. Also, we observe a strong non-random association between two of the viruses. The novel viruses have considerably more diversity than the previously known viruses. Chapter 4 investigated the effect of pesticides on viral and non-viral infection. I exposed Bombus terrestris colonies to field realistic doses of the neoticotinoid pesticide clothianidin in the laboratory, to the mimic pulsed exposure of crop blooms. I found some evidence for a positive effect of uncertain size on the infection rate of pesticide exposed colonies relative to non-pesticide exposed colonies, a potentially important result. Chapter 5 explored the evolution of avirulent multihost digital organisms across fluctuating fitness landscapes within a discrete sequence space. Consistent with theory, I found that evolution across a fluctuating discrete landscape leads to a faster rate of adaptation, greater diversity and greater specialism or generalism, depending on the correlation between the landscapes. A large range of factors are found to be important in the distribution of infection and diversity of viruses, and we find evidence for abiotic, biotic and anthropogenic factors all playing a role.
7
Santos, Maria Eduarda Alves dos. "Diversity and distribution patterns of order Zoantharia (Cnidaria: Anthozoa)." reponame:Repositório Institucional da UFPR, 2015. http://hdl.handle.net/1884/41121.
Full textAbstract:
Orientadora : Prof. Dr. Marcelo Visentini KitaharaOrientadora : Prof. Dr. James Davis Reimer
Dissertação (mestrado) - Universidade Federal do Paraná, Setor de Ciências da Terra, Programa de Pós-Graduação em Sistemas Costeiros e Oceânicos. Defesa: Pontal do Paraná, 10/12/2015
Inclui referências
Linha de pesquisa: Biologia e ecologia de sistemas oceânicos e costeiros
Resumo: Os padrões de diversidade nos oceanos são foco de teorias ecológicas e evolutivas. Estudos correlacionando dados filogenéticos e da distribuição de organismos permitem corroborar essas teorias que explicam os processos geradores da diversidade marinha. A compreensão desses processos também auxilia prever as consequências de eventos tais como alterações climáticas e bioinvasões Os animais da ordem Zoantharia (Cnidaria: Anthozoa) são encontrados da zona entremarés até profundidades abissais em todos oceanos. Zoantários formam extensas colônias, as quais servem de proteção e alimento para outros organismos. Apesar de serem um grupo de animais abundantes e cosmopolitas, dados sobre a distribuição das espécies ainda são escassos em diversos locais. Por exemplo, até a realização desta dissertação não haviam estudos investigando as espécies de Zoantharia da costa brasileira e sua distribuição nessa província. A falta de investigações sobre a diversidade do grupo é causada principalmente pela dificuldade de identificação das espécies, as quais apresentam uma grande plasticidade morfológica. Para solucionar essa dificuldade, estudos acoplando dados moleculares e taxonômicos mostram ser uma excelente forma de identificar esses animais. Dados moleculares também acresceram no conhecimento sobre a história evolutiva da ordem Zoantharia, um dos grupos que divergiram mais basais em Metazoa. Até o momento não foram estimadas relações filogenéticas do grupo utilizando todos as famílias/genêros com dados disponíveis em bases de dados tais como o GenBank. Em adição, dados moleculares indicam um relacionamento estreito entre espécies de zoantário dos oceanos Atlântico e Pacífico/Índico, entretanto nenhum trabalho investigou quais são são esses pares de espécie e que processos podem ter gerado esse padrão. O objetivo desta dissertação é contribuir na elucidação de padrões evolutivos nos oceanos, utilizando como modelo os zoantários. Nós analisamos as relações filogenéticas da ordem Zoantharia em dois aspectos complementares: 1) grandes clados e 2) espécies geneticamente próximas. Adicionalmente, nós relacionamos esses dados com ecologia e zoogeografia do grupo. No primeiro capítulo, a relação filogenética entre todas as famílias de Zoantharia é analisada em conjunto com as principais características ecológicas de cada clado. O segundo capítulo examina a diversidade e distribuição de zoantários no Atlântico sudeste, preenchendo a lacuna de conhecimento sobre o grupo na costa brasileira. Os resultados desse capítulo são utilizados também na investigação das espécies próximas de zoantários entre as duas bacias oceânicas (Oceano Atlântico e oceanos Pacífico e Índico) no terceiro capítulo.
Abstract: Diversity patterns in the oceans are focus of ecological and evolutionary theories. Studies correlating phylogenetic and distribution data of species allow support these theories which explain the processes generators of marine diversity. Undestand these processes also allow predict the consequences of events such as climate changes and bioinvasons. Animals of the order Zoantharia (Cnidaria: Anthozoa) occur from intertidal to abissal zones in all oceans. Species of the group are able to form extensive colonies that serve as shelter and food resource to other organisms. Althought zoantharian are abundant and cosmopolitan, distribution species data are still scass in several localities. For example, until the present research, there were no studies on Zoantharia species in brazilian coast. The lack of investigation of the group diversity is mostly due to the difficulties in species identification, which present a high interspecific morphological variability. In order to overcome this problem, studies using both morphological and molecular data have proven to be an excellent way to identify species. Molecular data have also provide a better knowledge on the evolution history of the group, however, there is no estimarion of phylogenetic relationships between all the genera with data avaialable in data bases such as GenBank. Moreover, molecular data indicated a close-related relationship between species on Atlantic Ocean and Pacific/Indian oceans, but no study have investigation which are these species. The goal of this dissertation is contribute in the elucidation of evolutionary patterns in the oceans, using as a model the zoantharians. We analyze phylogenetic relationships of the order Zoantharia in two complementary aspects: 1) large clades 2) close-related species. Furthemore, we linked these data with ecology and zoogeograpy of the group. In the first chapter, phylogenetic relationships between all Zoantharia families is analyzed along with their ecological traits. The second chapter examine diversity and distribution of zoantharians in southwest Atlantic, filling the gap of Zoantharia diversity in Brazil. Data of this study is also used in the investifation of close- related species between the two ocean basins (Atlantic Ocean and Pacific/Indian oceans) on the third chapter.
8
Smith, Joseph Alexander. "Mammalian Diversity and Distribution in Human-Altered Tropical Landscapes." Thesis, Imperial College London, 2009. http://hdl.handle.net/10044/1/4427.
Full textAbstract:
Habitat loss at the hands of human enterprise continues to drive the global decline inbiodiversity. While much attention has been placed on the use of protected areas as ameans of conservation, there is an increasing need to understand the capacity ofunprotected, human-altered landscapes to provide refugia and connectivity at largerspatial scales. This study evaluates the mammalian diversity that persists underalternative land management regimes and degrees of landscape change in south-centralSumatra, Indonesia. Species occurrence data compiled from extensive field surveysacross 1600km2 form the basis for analyses of community composition and speciesspecificresponses to the current landscape. Results indicate that species richnessdeclined with increased landscape alteration. The lowest observed species numberswere in areas of industrial scale oil palm production rather than scrub habitats ordegraded forest. Endangered mammals that persisted in the wider matrix were extirpatedfrom the oil palm dominated areas. Comparisons between the ecological traits shared bypersistent versus locally extirpated species revealed that in the initial stages of landscapechange there is the capacity to support large specialist species with slow life histories. Aslandscape degradation continues to an agricultural matrix only habitat and dietgeneralists persisted. Tests of species-specific responses to landscape alteration focussed on the occurrencepatterns of Sumatran tigers (Panthera tigris sumatrae) and four principal prey species. Measures of human prevalence derived from survey data and a novel application ofoccupancy estimation techniques, identified significant negative responses to higherlevels of landscape development. Satellite derived measures of habitat connectivity andlocalised landcover degradation found that connectivity to areas of least disturbed forestwas more important for reclusive species such as tapir (Tapirus indicus) and red muntjac(Muntiacus muntjak), while the occurrence of the wide-ranging tiger was more stronglyinfluenced by local landcover degradation. The capacity of human altered landscapes tocontribute to the conservation of mammalian communities is closely allied to theavailability of degraded forests rather than alternative human altered landcovers. Giventhat these areas of forest are increasingly subject to degradation and conversion, spatialplanning and proactive management are required to safeguard these resources.
9
Sanyika, Walter Tendai. "Comparison of actinobacterial diversity in Marion Island terrestrial habitats." Thesis, University of the Western Cape, 2008. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_2619_1263423621.
Full text
10
Suija, Ave. "Lichens and lichenicolous fungi in estonia: diversity, distribution patterns, taxonomy /." Online version, 2005. http://dspace.utlib.ee/dspace/bitstream/10062/810/5/suija.pdf.
Full text
11
Brown, J. K. "Diversity and Global Distribution of Whitefly-Transmitted Geminiviruses of Cotton." College of Agriculture, University of Arizona (Tucson, AZ), 1998. http://hdl.handle.net/10150/210399.
Full textAbstract:
Geminivirus diseases of cotton are on the rise, worldwide, yet few have been studied in adequate detail to permit the implementation of rational approaches to disease control. The rising costs of managing the whitefly vector, coupled with substantial losses caused by geminivirus-incited diseases now hinder cotton production by requiring inputs that are beyond economic feasibility. The need for geminivirus disease resistant cultivars in diverse cotton producting areas and against different viral genotypes presents a new challenge. To meet this need, information about the identity, distribution, and relevant biotic characteristics of cotton -infecting geminiviruses is needed This project addresses this problem through the molecular analysis of the genomes of cotton-infecting geminivirus from cotton throughout the world Here, sequence similarities of the coat protein gene and of the non-coding IR/CR involved in regulating virus replication and transcription were examined by comparative sequence analysis to achieve virus identification. This is the first effort to determine virus identity and to map the distribution of geminiviruses on a global basis. The outcome of this effort will be a data base containing biotic and molecular information that will permit rapid and accurate geminivirus identification, and the selection of relevant viral species for development of cotton cultivars with disease resistance to the geminiviruses specific to individual production areas.
12
Mansfield, Fiona Kerrie. "Allometric scaling in bacterial populations : cell size, distribution and diversity." Thesis, Imperial College London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424704.
Full text
13
Sutton, D. J. "Diversity and spatial distribution of carabid beetles in Bernwood forest." Thesis, Oxford Brookes University, 1988. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.379683.
Full text
14
Thaler, Mary. "Diversity and distribution of heterotrophic flagellates in the Arctic Ocean." Thesis, Université Laval, 2014. http://www.theses.ulaval.ca/2014/30411/30411.pdf.
Full textAbstract:
Dans les environnements marins arctiques, les protistes unicellulaires constituent les premiers maillons du réseau trophique. Les flagellés hétérotrophes (HF) jouent un rôle clé au sein de ce réseau trophique comme brouteurs de bactéries et de phytoplanctons, étant broutés à leur tour par les microzooplanctons comme les dinoflagellés ou les ciliés. Les scientifiques prévoient que les changements environnementaux extrêmes qui ont présentement lieu dans l’Océan Arctique transformeront ces communautés de protistes. Le sujet de cette thèse porte sur la composition taxonomique des communautés marines HF dans l’Océan Arctique, et leur réponse aux facteurs environnementaux. L’approche a été d’utiliser le comptage sur microscope à l’aide de l’hybridation fluorescente in situ pour évaluer l’abondance de deux taxons HF importants, le genre Cryothecomonas et le clade MAST-1 parmi les straménopiles marins. Une approche complémentaire a été de décrire la répartition de tous les taxons HF, y compris l’ordre Cryomonadida, les straménopiles marins, Picozoa, Telonemia, et les choanoflagellés, par l’utilisation du séquençage à haut débit. Les résultats des deux approches nous ont permis de capturer les tendances environnementales sur une large échelle géographique dans l’Arctique. Il a été mis en évidence une composition taxonomique structurée, principalement dû à l’influence de la glace de mer et d’autres facteurs environnementaux. Les cellules de Cryothecomonas semblaient provenir de la glace de mer, et au sein de la colonne d’eau ils se trouvaient les plus nombreuses près du bord de glace. Par contre, les trois sous-clades de MAST-1 étaient retrouvés principalement dans la colonne d’eau, mais répartis différemment par rapport au couvert de glace et les zones marginales de glace. La composition de la totalité de la communauté HF variait aussi par région, avec une plus grande importance de Telonemia et des choanoflagellés dans le Bassin du Canada. Pour plusieurs taxons, nous avons pu identifier un ou deux phylotypes dominants pour une région donnée. L’importance relative de ces taxons devrait changer lors de la retraite de glace continue dans l’Arctique, menant à des changements importants dans les réseaux trophiques et les cycles biogéochimiques.In marine environments, single-celled protists form the initial links of the food web. Heterotrophic flagellates (HF) play a key role by grazing on bacteria and phytoplankton, being grazed upon in their turn by microzooplankton such as dinoflagellates and ciliates. The extreme environmental changes currently taking place in the Arctic Ocean are expected to transform protist communities. The subject of this thesis is the taxonomic composition of marine HF communities in the Arctic Ocean, and their response to environmental factors. The approach was to use fluorescent oligonucleotide probes to assess the abundance of two important HF taxa, the genus Cryothecomonas and the clade MAST-1 of the marine stramenopiles, via microscope counts. A complementary approach was to describe distribution of all HF taxa, including Cryomonadida, marine stramenopiles, Picozoa, Telonemia and choanoflagellates, by means of high-throughput sequencing. Results from these two approaches allowed us to capture broad environmental trends over a large geographic scale in the Arctic. A picture emerged of taxonomic composition largely structured by the influence of sea ice and other environmental factors. Cryothecomonas cells are inferred to live principally in the sea ice, and in the water column are more numerous close to the ice edge, whereas three sub-clades of MAST-1 are all found principally in the water column but are distributed differently relative to ice cover and marginal ice zones. The composition of the total HF community also varied by region, with a greater importance of Telonemia and choanoflagellates in the Canada Basin. For several taxa it was possible to identify one or two dominant phylotypes in a given region. The relative importance of these taxa is expected to change as sea ice retreat continues in the High Arctic, leading to important changes in trophic webs and biogeochemical cycles.
15
Gaonkar, Chetan Chandrakant. "Diversity, distribution and evolution of the planktonic diatom family Chaetocerotaceae." Thesis, Open University, 2017. http://oro.open.ac.uk/50352/.
Full textAbstract:
The number and abundance of diatom species in environmental samples are counted traditionally by means of light microscopy (LM). However, recognizing –let alone, counting- species is often challenging because of the existence of cryptic species and intraspecific phenotypic plasticity. Proper characterization requires isolation of cells, growing them into monoclonal cultures, and characterizing the cultures genetically and morphologically. However, not all species grow in culture, featureless ones are less likely to be isolated, and the procedure is laborious. High-throughput sequencing (HTS) metabarcoding bypasses morphology; DNA is collected from environmental samples, a particular marker sequenced, and the resulting sequences sorted into clusters or terminal clades assumed to represent species. Yet, reference barcodes of taxonomically validated species are needed to identify these clades. This exercise is the main aim of my thesis. Since it is impossible to do this for all the diversity within a PhD thesis project, we selected Chaetocerotaceae, an abundant and diverse family of marine planktonic diatoms, containing two genera: Chaetoceros and Bacteriastrum. Its members uniquely share setae; thin siliceous tubes emerging from the valve corners, facilitating detection in samples. Strains were obtained from the Gulf of Naples (GoN), from Central Chile and Roscoff – at sites for which LTER time series data are available. A total of 270 strains were obtained from these sites, and their 18S- and partial 28S rDNA sequences and morphological information gathered. The strains grouped into 60 genetically distinct species, thus providing a dataset of validated Chaetocerotacean 18S reference barcodes. Inferred molecular phylogenies showed monophyletic Chaetocerotaceae as well as monophyletic Bacteriastrum inside paraphyletic Chaetoceros, and the presence of cryptic diversity. To start with taxonomic updates, the species C. sporotruncatus and C. dichatoensis were described within the C. socialis species-complex based on spore morphology and sequence differences. Several rDNA sequences contained spliceosomal introns (ca. 100bp) and/or group-I introns (ca. 400bp). Phylogenies inferred from the introns did not corroborate rDNA phylogenies, suggesting horizontal gene transfer. Presence/absence of introns in conspecific strains sampled in different seasons suggests population differentiation between these seasons. A HTS dataset consisting of V4-sequences (part of 18S) from 48 seawater samples taken over the seasons in the GoN revealed 76 terminal clades of which 46 grouped with a reference barcode. Some of these species occur year-round whereas most others are seasonal. Surprisingly, of the 30 clades belonging to unknown Chaetocerotacean species, two appear to be among the most abundant in the GoN.
16
Roth, Cali Lynn. "The impact of topographic variation on invertebrate distribution and diversity." Kent State University / OhioLINK, 2014. http://rave.ohiolink.edu/etdc/view?acc_num=kent1406330513.
Full text
17
Brummitt, Neil Alistair. "Patterns in the diversity and distribution of flowering plant genera." Thesis, University of Edinburgh, 2005. http://hdl.handle.net/1842/27446.
Full textAbstract:
Regional distributions of all vascular plant genera have been compiled from herbarium specimens at the Royal Botanic Gardens, Kew, and this data has then been analysed for large-scale patterns in the diversity and distribution of flowering plants, at both genus and family levels. A strong latitudinal gradient in diversity is apparent at family, genus and species levels, though while western South America is most diverse at species and genus levels, it is the SW. Pacific which is most diverse at family level. However, the number of families and genera per region is very strongly correlated, irrespective of the region. There is a very strong relationship between both family and genus diversity and area, though not for numbers of endemic genera. Analysing floristic similarity between different regions of the world reveals very strongly supported continental groups, since most genera are confined to particular continents, although the latitudinal difference between regions is a better predictor of floristic similarity than is simply distance between regions. Latitudinal range-size for genera increases towards the equator, although taxon-size in general decreases with increasing latitudinal range-size. For both families and genera, the range-size frequency distribution is highly skewed towards small range sizes (more so for genera than families), which account for the majority of taxa. Distribution patterns show strong regional clustering, with almost 40% of genera single-region endemics, and approximately 20% of world distribution patterns accounting for about 80% of total angiosperm genus diversity. Analysis of these distribution patterns reveals a strong correlation between diversity and the number of floristic elements, which intersect to form the diversity of a region.
18
Baena, Susana. "Remotely sensed solutions for plant diversity conservation." Thesis, University of Nottingham, 2018. http://eprints.nottingham.ac.uk/51765/.
Full textAbstract:
Global change is happening at a staggering pace and the impact that change is having in the loss of plant biodiversity is unprecedented. The latest reports on the state of the world’s plants indicate that they face intensifying threats and biodiversity loss on a global scale. However, this rapid global change is also bringing extraordinary technological developments to all scientific fields. Earth Observation by Remote Sensing is undergoing a fast expansion and its capacity to monitor and analyse global environmental changes and their impact in biodiversity is ever growing. This research analyses the current and potential role of Earth Observation in the conservation of plant diversity, identifying the latest technological developments with the greatest potential use in this field. Looking into a plant conservation organisation and through a series of case studies covering a range of spatial and temporal scales, this research brings the latest Remote Sensing technology to the plant conservation community. From collecting and processing very high resolution data for local conservation projects to help determine conservation status of a country’s unique ecosystem to tracking and reporting on global plant conservation targets this research demonstrates that Remote Sensing is instrumental for addressing the observation needs of the plant conservation community.
19
Cuvelier, Marie Laure. "New Insights into the Diversity, Distribution and Ecophysiology of Marine Picoeukaryotes." Scholarly Repository, 2010. http://scholarlyrepository.miami.edu/oa_dissertations/657.
Full textAbstract:
Marine microbes are an essential component of global biogeochemical cycles. In oligotrophic marine surface waters, the phytoplankton, phototrophic, single-celled (on occasion, colonial) organisms, is often dominated by the picoplankton (cells <2 micrometers in size), which constitute the base of the marine food chain. The picophytoplankton is composed of three main groups of organisms: two genera of cyanobacteria, Prochlorococcus and Synechococcus, and a third group, the picoeukaryotes. Even though numerically less abundant than cyanobacteria, picoeukaryotes can contribute significantly to biomass and primary production in this size fraction. Furthermore, picoeukaryotes are a diverse group but this diversity is still underexplored and their ecological roles and physiology is poorly understood. Here uncultured protists are investigated using 18S rRNA gene clone libraries, phylogenetic analyses, specific fluorescence in situ hybridization (FISH) probes and other methods in tropical and subtropical waters. Gene sequences comprising a unique eukaryotic lineage, biliphytes, were identified in most samples, whether from high (30 degrees Celsius) or low (5 degrees Celsius) temperature waters. Sequences within this uncultured group have previously been retrieved from mid and high latitudes. Phycobilin-like fluorescence associated with biliphyte-specific FISH probed cells indicated they may be photosynthetic. Furthermore, the data indicated biliphytes are nanoplanktonic in size, averaging between 3.0 and 4.1 micrometers. Using the 18S rRNA gene, sequences belonging to a broadly distributed but uncultivated pico-prymnesiophytes were retrieved. We investigated the ecological importance of these natural pico-prymnesiophyte populations and field experiments showed that they could grow rapidly and contributed measurably to primary production. They also appear to form a large portion of global picophytoplankton biomass, with differing contributions in five biogeographical provinces, from tropical to high latitudes. Finally, the physiology of the picoeukaryote Micromonas was studied under a shift from medium to high light and UV radiation. Results showed that the growth of these photosynthetic cells was synchronized with the light: dark period. Forward angle side scatter and red autofluorescence from chlorophyll increased throughout the light period and decreased during the dark period. This is consistent with cell division occurring at the beginning of the dark period. Additionally, genes proposed to have roles in photoprotection were up-regulated under high light and UV, but not in controls.
20
Kataržytė, Marija. "Hypogeous fungi of Lithuania: diversity, distribution and links with small mammals." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2009. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2009~D_20090507_135047-17978.
Full textAbstract:
Hypogeous fungi perform various functions in the forest ecosystems, they form the mycorrhizal relationship with plants and serve as the food source of some animals. Main aims of this dissertation were to ascertain the diversity and distribution of hypogeous fungi in Lithuania, to compare the communities of hypogeous and epigeous mycorrhizal fungi, and to explore the composition of fungi in small mammal diet. Using various research methods (an analysis of the literature data, the critical examination of the herbarium specimens, the search of the fruit-bodies by raking the soil, an examination of the fecal pellets of small mammals) in total 29 species of hypogeous fungi have been ascertained in Lithuania. The taxonomic structure, distribution and fructification phenology of hypogeous fungi has been analysed. The data on the structure and dynamics of communities of hypogeous and epigeous mycorrhizal fungi in spruce, oak and mixed tree stands were presented. The influence of abiotic and biotic factors on the species composition and fructification of fungi was assessed. The peculiarities of small mammal mycophagy in different tree stands were described.Požeminiai grybai atlieka įvairias funkcijas miško ekosistemose, sudaro mikorizes su augalais ir yra kai kurių gyvūnų maisto šaltinis. Disertacinio darbo pagrindiniai tikslai buvo išaiškinti Lietuvos požeminių grybų rūšių įvairovę ir paplitimą, palyginti mikorizinių požeminių ir antžeminių grybų bendrijas, išaiškinti grybų sudėtį smulkiųjų žinduolių maisto racione. Pritaikius skirtingus tyrimo metodus (literatūros duomenų analizę, kritišką herbariuminių pavyzdžių tyrimą, grybų vaisiakūnių paiešką grėbliukais suardytame dirvožemyje, smulkiųjų žinduolių ekskrementų tyrimą), nustatyta, kad dabar Lietuvoje žinomos 29 požeminių grybų rūšys. Išnagrinėta požeminių grybų taksonominė struktūra, paplitimas ir fruktifikacijos fenologija. Pateikti duomenys apie požeminių ir antžeminių mikorizinių makromicetų bendrijų struktūrą ir dinamiką eglynuose, ąžuolyne ir mišriame medyne. Įvertinta abiotinių ir biotinių veiksnių įtaka grybų rūšių sudėčiai ir fruktifikacijai. Išnagrinėti kai kurių smulkiųjų žinduolių mikofagijos ypatumai skirtingos sudėties medynuose.
21
Nigro, Lisa M. "Distribution and Diversity of Bacterial Chemolithotrophs in Marine and Freshwater Sediments." Fogler Library, University of Maine, 2006. http://www.library.umaine.edu/theses/pdf/NigroLM2006.pdf.
Full text
22
Bennett, Nicholas Charles. "The Transforming Diversity and Variability of Film Exploitation, Distribution and Consumption." Thesis, The University of Arizona, 2013. http://hdl.handle.net/10150/297493.
Full textAbstract:
This paper aims to discuss how the changing perception of film accessibility affects the exploitation and distribution of movies. Films are now seen as an extremely available and far-' reaching source of entertainment, and consumers have recently adapted in new ways due to the advent of new technological movie-viewing resources. The emergence of consumers who have the ability to watch their favorite movies on a small, handheld tablet demonstrates just how far the distribution of film has come. With many new options to find and watch movies, a person's preferences and schedule can typically be matched with some form of viewing technology. This new widespread availability of film, and how young consumers view films, will be the basis of this thesis, focusing upon college undergraduates and their common behaviors of seeking and viewing movies and in-depth research on the changes of the industry. A series of four studies were conducted to explore the movie viewing behaviors and preferences of undergraduate students and the University of Arizona.
23
Huddleston, Annaliesa S. "The distribution and diversity of streptomycin-producing streptomycetes in Brazilian soil." Thesis, University of Warwick, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.484192.
Full text
24
Rahman, Thahira J. "The diversity and distribution of thermophilic bacteria in cool soil environments." Thesis, University of Ulster, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.422883.
Full text
25
Rowlands, Gwilym. "Remote Sensing the Diversity, Distribution and Resilience of Coral Reef Environments." NSUWorks, 2013. http://nsuworks.nova.edu/occ_stuetd/75.
Full textAbstract:
Chapter 2:
This chapter introduces the five study sites (Ras Al‐Qasabah; Al Wajh; Yanbu; Farasan Banks; and Western Farasan Islands) along with the fieldwork and detailed benthic mapping and bathymetry mapping conducted in the Saudi Arabian Red Sea. In the Western Farasan Islands two candidate mapping technologies were compared. Firstly, the QuickBird multispectral satellite sensor and secondly the CASI‐550 airborne hyperspectral sensor. In processing the CASI imagery, it was necessary to customize processing to correct for an unusual across‐track artifact caused by lens condensation. On the basis of cost, logistical constraints, spectral reliability, and project needs, multispectral imagery was found to be the most appropriate technology for regional‐scale mapping. Over 20,000 sq. km of high quality QuickBird imagery were amassed across the five study sites. This represents approximately half the shallow water (<20 m) environment of the Saudi Arabian Red Sea. The work presented in this chapter provides a blueprint for processing such large image data sets. Maps with a minimum mapping unit (MMU) of 7.5 sq. m, and a thematic resolution of fifteen habitat classes were produced at an overall accuracy (Tau statistic) of 70%. The five study sites were found to differ substantially in terms of the type, quantity and spatial arrangement of habitats present. The study illustrates the power of remote sensing for delivering regional‐scale audits of coral reef environments.
Chapter 3:
Coral reefs and their associated accumulations of carbonate sediment adopt particularly complex planform geometries atop the coastal shelf of the Saudi Arabian Red Sea. By assembling 95,000 sq. km of remote sensing data into a GIS, this study aims to relate the morphology of these shallow‐water depositional environments to processes that sculpt the coastal zone. A typology is developed that sorts carbonate systems into end‐members on the basis of their morphology and relationship to the coastline. The resulting GIS was interrogated for spatial patterns in the distribution and abundance of the end‐members. While several depositional morphologies are present throughout the length of the Saudi Arabian Red Sea, the occurrence of others is restricted to narrow regions of latitude. Such differences in distribution can be explained in process‐terms by the rift tectonics of the Red Sea basin, spatial variability in the presence of sub‐seafloor evaporites, and the input of siliciclastic detritus onto the coastal shelf via wadis. This chapter provides a foundation for understanding the morphological diversity of shallow‐water carbonate systems in both the modern ocean and rock record.
Chapter 4:
In this chapter a framework is proposed for spatially estimating a proxy for coral reef resilience using remote sensing. Data spanning over 20,000 sq. km of coral reef habitat were obtained using the commercial QuickBird satellite, and freely available imagery (NASA, Google Earth). Principles of coral reef ecology, field observation, and remote observations, were combined to devise mapped indices. These indices capture important and accessible components of coral reef resilience. Indices are divided between factors known to stress corals, and factors incorporating properties of the reef landscape that resist stress or promote coral growth. The first‐basis for a remote sensed resilience index (RSRI), an estimate of expected reef resilience, is proposed. Developed for the Red Sea, the framework of the analysis is flexible and with minimal adaptation, could be extended to other reef regions. The chapter illustrates how remote sensing can be used to deliver more than simply habitat maps of coral reefs.
Chapter 5:
In this chapter, a fundamental measure of coral reef health, coral cover, is assessed in relation to two physical parameters, water depth and wave height. Light availability declines rapidly with depth, which influences the photosynthetic productivity of coral. Where waves break, they produce a severe increase in marine turbulence, and generate currents that may extend beyond the surf zone. The study is focused on the Farasan Banks where some 4000 sq. km of reef habitat are spread across 12,000 sq. km of the Saudi Arabian coastal shelf. The size of the system creates logistical challenge for standard field‐based monitoring methodologies, such as SCUBA surveys. Here, rapid video assessments were employed to deliver measures of coral health across eight percentage cover classes at 472 locations. Whilst water depth can be reliably derived from satellite, assessing wave height is problematic since the parameter is both spatially and temporally variable. Using daily, satellite derived meteorology, a spatially explicit wave model was developed spanning the nine year period from 1999 to 2008. For the majority of the
video sites in the Farasan Banks, coral cover was found to be <11%. This statistic hides the counter trend, however that there are robust patterns in higher coral abundance that can be characterized by water depth and wave height. In the inshore, wave height had little bearing on coral cover, instead video sites with a high coral cover were found with a greater probability in shallow (<9m, reef environments. In the offshore, wave exposure exercises stronger control on coral cover than in the inshore, such that video sites with a coral cover greater than 50% were exclusively found in areas where significant wave height exceeds 2 m. The water depth at which the highest coral cover occurs is also deeper offshore than inshore. Once quantified, the conservative behavior of coral cover with respect to water depth and hydrodynamic exposure offers relevant insight to the management of coral reef environments at regional extent.
Chapter 6:
Carbonate sequence stratigraphy is founded on the principle that changes in relative sea level are recorded in the rock record by the accumulation of sediment with relative‐water‐depth dependent attributes. While at the scale of a shelf‐to‐basin transect, facies clearly stratify by water depth, the relationship blurs for depths <40 m, the most vigorous zone of carbonate production, where the intrinsic processes of storm and wave reworking influence the seabed through submarine erosion and sediment redistribution. Remote sensing imagery, field observations, and hydrodynamic models for two reef‐rimmed shore‐attached carbonate platforms in the Red Sea show neither water depth nor energy regime to be reliable indicators of facies type when considered in isolation. Considered simultaneously, however, the predictive power of the two variables rises significantly. The results demonstrate it to be an oversimplification to assume a direct link between palaeo‐water depth and depositional lithofacies diversity, while highlighting the importance of hydrodynamics in directing the accumulation of carbonate sediments in the shallow photic zone. While the size distributions of facies in the two focus areas, Al Wajh and Ras Al‐Qasabah, follow power laws, no direct relationship between the lateral continuity of the facies belts and water depth or wave height are reported. The work is relevant for the interpretation of meter‐scale subtidal carbonate cycles throughout the geologic record.
26
Kemp, Joanna Lynn. "Physical controls on the diversity and distribution of river channel habitats." Thesis, University of Leicester, 1999. http://hdl.handle.net/2381/29795.
Full textAbstract:
This study investigated the relationship between in-channel physical conditions and the diversity and distribution of macroinvertebrate habitats, known as 'functional habitats'. The Welland, Nene, Ouse and Deben catchments, in the English lowlands, were studied during the summer months of 1995 and 1996. The physical conditions, in terms of depth, velocity and Froude number, associated with each of the functional habitats were identified. The relationship between functional habitat diversity and the in-stream physical environment was examined at two levels: the cross-section and the 50 m reach. Habitat diversity in a cross-section was highest in 'riffle-like' as opposed to 'pool-like' conditions. Cross sections with a high coefficient of Froude number variation were also associated with high habitat diversity. No strong seasonal trends were observed, from early to late summer, in either physical variables, functional habitat diversity or habitat abundance (except for a small change in velocity). Habitat diversity in a reach was highest when the river was found to have a 'natural' channel width and was reduced if the river deviated greatly from its 'natural' (predicted) width. Two types of physical channel degradation led to the river being wider that predicted. These were 'over-widening' and 'ponding'. Sites with these conditions contained a characteristic functional habitat frequently; over-widened reaches were dominated by 'silt' and 'emergent macrophytes' while ponded reaches were dominated by 'floating-leaved macrophytes' and 'macroalgae'. Functional habitat diversity was positively related to spatial heterogeneity at the reach scale. It was highest where 65% of the reach was less than 40 cm deep, and lowest when the reach was uniformly shallow or deep.
27
Park, Sungkyu. "Cyclotides evolve : Studies on their natural distribution, structural diversity, and activity." Doctoral thesis, Uppsala universitet, Avdelningen för farmakognosi, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-292668.
Full textAbstract:
The cyclotides are a family of naturally occurring peptides characterized by cyclic cystine knot (CCK) structural motif, which comprises a cyclic head-to-tail backbone featuring six conserved cysteine residues that form three disulfide bonds. This unique structural motif makes cyclotides exceptionally resistant to chemical, thermal and enzymatic degradation. They also exhibit a wide range of biological activities including insecticidal, cytotoxic, anti-HIV and antimicrobial effects. The cyclotides found in plants exhibit considerable sequence and structural diversity, which can be linked to their evolutionary history and that of their host plants. To clarify the evolutionary link between sequence diversity and the distribution of individual cyclotides across the genus Viola, selected known cyclotides were classified using signature sequences within their precursor proteins. By mapping the classified sequences onto the phylogenetic system of Viola, we traced the flow of cyclotide genes over evolutionary history and were able to estimate the prevalence of cyclotides in this genus. In addition, the structural diversity of the cyclotides was related to specific features of the sequences of their precursor proteins, their evolutionary selection and expression levels. A number of studies have suggested that the biological activities of the cyclotides are due to their ability to interact with and disrupt biological membranes. To better explain this behavior, quantitative structure-activity relationship (QSAR) models were developed to link the cyclotides’ biological activities to the membrane-interactive physicochemical properties of their molecular surfaces. Both scalar quantities (such as molecular surface areas) and moments (such as the distributions of specific properties over the molecular surface) were systematically taken into account in the development of these models. This approach allows the physicochemical properties of cyclotides to be geometrically interpreted, facilitating the development of guidelines for drug design using cyclotide scaffolds. Finally, an optimized microwave-assisted Fmoc-SPSS procedure for the total synthesis of cyclotides was developed. Microwave irradiation is used to accelerate and improve all the key steps in cyclotide synthesis, including the assembly of the peptide backbone by Fmoc-SPPS, the cleavage of the protected peptide, and the introduction of a thioester at the C-terminal carboxylic acid to obtain the head-to-tail cyclized cyclotide backbone by native chemical ligation.
28
Harwood, Peter, Christopher Wilson, Arthur Sullivan, and Eugene Augustin. "LOW COST, HIGHLY TRANSPORTABLE, TELEMETRY TRACKING SYSTEM FEATURING THE AUGUSTINE/SULLIVAN DISTRIBUTION AND POLARIZATION, FREQUENCY AND SPACE DIVERSITY." International Foundation for Telemetering, 1996. http://hdl.handle.net/10150/608364.
Full textAbstract:
International Telemetering Conference Proceedings / October 28-31, 1996 / Town and Country Hotel and Convention Center, San Diego, CaliforniaThe tracking system is part of a telemetry ground station being developed for the UK Ministry of Defence. The design objective is a self-contained transportable system for field use in a vehicle or workshop environment, so that the system components are required to be man portable. Comprehensive facilities are required for the reception, display and analysis of telemetry data from a remote 1430-1450MHz airborne source at ranges of up to 205km. Since tracking over water is a prime requirement the system must accommodate severe multipath fading. A detailed analysis of the link budget indicates that there is a major conflict between cost, portability, antenna size and the receiver complexity required to achieve a satisfactory performance margin. A baseline system is analysed using a four foot antenna. Methods for improving the performance are then considered including polarisation, frequency and space diversity coupled with alternative antenna types and configurations. The optimum solution utilises two six foot diameter shaped beam single axis antennas of unique design in conjunction with a receiving system which economically combines the elements of polarisation, frequency and space diversity.
29
Zhang, Jianhua. "Diversity of aster yellows phytoplasmas in lettuce." The Ohio State University, 2004. http://rave.ohiolink.edu/etdc/view?acc_num=osu1054584888.
Full text
30
Long, Rachel May. "The distribution and diversity of PAC-degrading bacteria and key degradative genes." Thesis, University of Exeter, 2008. http://hdl.handle.net/10036/65303.
Full textAbstract:
Petroleum hydrocarbons are the most widespread contaminants in the environment. Interest in the biodegradation of polycyclic aromatic hydrocarbons and compounds (PAHs/PACs) is motivated by their ubiquitous distribution, their low bioavailability, high persistence in soils and their potentially deleterious effects to human health. Identifying the diversity of microorganisms that degrade PAHs/PACs can be utilised in the development of bioremediation techniques. Understanding the mechanisms of bacterial populations to adapt to the presence of pollutants and the extent that lateral transfer of key functional genes occurs, will allow the exploitation of microbial PAC/PAH-degradative capabilities and therefore enhance the successful application of bioremediation strategies. A key aim of this study was to isolate and identify PAC-degrading bacteria for potential use in future bioremediation programmes. A series of PAC enrichments were established under the same experimental conditions from a single sediment sample taken from a highly polluted estuarine site. Distinct microbial community shifts were directly attributable to enrichment with different PAC substrates. The findings of this study demonstrate that five divisions of the Proteobacteria and Actinobacteria can degrade PACs. By determining the precise identity of the PAC-degrading bacteria isolated, and by comparing these with previously published research, this study showed how bacteria with similar PAC degrading capabilities and 16S rRNA signatures are found in similarly polluted environments in geographically very distant locations e.g. China, Italy, Japan and Hawaii. Such a finding suggests that geographical barriers do not limit the distribution of key PAC-degrading bacteria. This is significant when considering the diversity and global distribution of microbes with PAC-degradative capabilities and the potential for utilising these microbial populations in future bioremediation strategies. In the laboratory, enrichment of bacteria able to utilise PAHs has commonly been performed in liquid media, with the PAH dissolved in a carrier solvent. This study found the presence of a carrier solvent significantly affects the resultant microbial population. Although the same sediment sample was used as the bacterial source in all enrichments, different bacterial strains were obtained depending upon the presence of the carrier solvent and the PAH. This is important when considering appropriate methodology for the isolation of PAH-degrading bacteria for future bioremediation programmes. Additionally, the species comprising the resultant population of the enrichment when a carrier solvent was present were similar to previously reported PAH-degrading species. Such a finding necessitates review of previously reported PAH-degrading bacterial species that have been isolated and identified from enrichments using a carrier solvent. Understanding how bacteria acclimatise to environmental pollutants is vital for exploiting these mechanisms within clear up strategies of contaminated sites. Two major lineages of the α subunit of PAH dioxygenases were identified: Actinobacteria and Proteobacteria. Comparison of the α subunit phylogeny with the 16S rRNA phylogeny implies that the PAH-dioxygenases evolved prior to the separation of these phyla or that lateral transfer occurred in the very distant past. No evidence for lateral transfer of the α subunit between the Actinobacteria and Proteobacteria was found in the phylogenetic analyses of this research. Multiple lateral transfer events were inferred between the species of the Actinobacteria and between the classes of the Proteobacteria. The clustering of the taxa within the α subunit phylogeny indicates that lateral transfer of the α subunit gene occurred after the separation of the classes of Proteobacteria and also after the speciation of the γ-Proteobacteria. These findings reveal how bacteria have acclimatised to PAH pollutants through multiple lateral transfer events of a key PAH-degradative gene. This knowledge of the transfer of genetic material will broaden our prospects of exploiting microbial populations.
31
Mannion, P. D. "Environmental and geological controls on the diversity and distribution of the sauropodomorpha." Thesis, University College London (University of London), 2010. http://discovery.ucl.ac.uk/20238/.
Full textAbstract:
Sauropodomorph dinosaurs were an important component of Mesozoic terrestrial ecosystems. Their diversity and abundance fluctuated throughout the Mesozoic but whether this reflects genuine biological changes or merely variations in our sampling of the rock record is uncertain. A database of all sauropodomorph individuals (2335) has been compiled, including environmental, geological, taxonomic and taphonomic data. Using a variety of sampling proxies (including a new specimen completeness metric) and a number of analytical techniques (residuals, rarefaction and phylogenetic diversity estimates), this work has demonstrated that sauropodomorph diversity appears to be genuinely high in the Pliensbachian‐Callovian and Kimmeridgian‐Tithonian, while low diversity levels are recorded for the Oxfordian and Berriasian‐Barremian, with the J/K boundary seemingly representing a real diversity crash. Diversity in the remaining Triassic‐Jurassic stages appears to be largely controlled by sampling biases while Late Cretaceous diversity is difficult to elucidate and perhaps remains relatively under‐sampled. Sea level affects diversity and abundance in the Jurassic‐Early Cretaceous, but does not appear to be linked in the Late Cretaceous. Different clades of sauropodomorphs potentially preferred different environments and this may have had an effect on changes in their distribution and diversity. Titanosaurs have been demonstrated to show a preference for inland environments compared to non‐titanosaurs, and it is possible that this led to their success in the Cretaceous when other sauropod clades were in decline. An assessment of the palaeolatitudinal patterns of sauropods and ornithischians reveals a distributional skew in the Late Cretaceous, which may reflect environmental and/or dietary preferences. A study of completeness through historical time contradicts the recent claim that the quality of dinosaurian type material has improved from the 19th century to the present. These studies illustrate that use of a number of techniques is imperative in any attempt to tease apart genuine patterns from the biases of an uneven rock record.
32
Chawdhri, Rizwana F. "The distribution and diversity of nucleoside N-deoxyribosyltransferase among lactic acid bacteria." Thesis, University of Warwick, 1992. http://wrap.warwick.ac.uk/2986/.
Full textAbstract:
Nucleoside N-deoxyribosyltransferases are capable of synthesising stereoand regioselectively a variety of 2'-deoxy- and 2', 3'-dideoxyribonucleosides. These compounds could be effective as inhibitors of reverse transcriptase, by acting as DNA chain terminators. The enzyme has been found previously only in a small number of microorganisms of the genus Lactobacillus. In the present study, phosphate-independent nucleoside N-deoxyribosyltransferase activity was detected in cell-free extracts from the genera Aerococcus, Pediococcus, LeuconostocS, treptococcus, Lactococcus and also more widely among the subgroups of Lactobacillus. From this screening study, it was found that only purine-specific N-deoxyribosyltransferase activity was present in Lactobacillus salivarius subsp. salivarius, suggesting that this strain lacked an enzyme analogous to N-deoxyribosyltransf erase II. Leucollostoc mesenteroides subsp. cremoris was found to express the highest N-deoxyribosyltransferase specific activity towards pyrimidines and purines. As N-deoxyribosyltransferase activity had not been detected in strains of Leuconostocb efore, the enzyme was purified and characterised from Leu. mesenteroidess ubsp. cremoris. A single multifunctional enzyme capable of carrying out the transfer of the deoxyribosyl moiety from either pyrimidine or purine nucleosides to either pyrimidine or purine bases was found to be present in this strain of Leucoizostoc.A. four-step procedure employing affinity chromatography was used to purify the enzyme to homogeneity. Kinetic studies carried out on the purified enzyme showed that the transfer reactions ocurred via a ping-pong mechanism. Evidence was also provided by radiolabelling studies of a glycosyl-enzyme intermediate forming when the first substrate, the nucleoside donor, bound to the enzyme.
33
Brooks, Bjorn-Gustaf James. "Computational geological approaches for assessing the diversity and ecological distribution of fossils." [Ames, Iowa : Iowa State University], 2009.
Find full text
34
Mucciolo, Serena. "Polychaete fauna of the Northwest Portuguese Coastal Shelf: ecology, diversity and distribution." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2015. http://amslaurea.unibo.it/9640/.
Full textAbstract:
Polychaetes are one of the larger groups of macroinvertebrates with more than 9000 species recognised, distributed worldwide. Thanks to the broad ecological adaptability and high abundaces, this taxon plays a leading role and is considered an important component of all benthic assemblages.
Our knowledge about the West Iberian Coast polychaete fauna are scarce, and the only studies are recent. In this sense, the aim of this work was to investigate the composition and the spatial distribution of the polychaete fauna along the NW Portuguese Coastal Shelf, focusing on their relationship to environmental factors (depth, grain size, longitude and latitude) and to add new data to the existing biological dataset. A total of 39 sites were analysed, collected in an area of about 5665 km², between 20 and 150 m depth, distributed in a way to cover the overall grain size gradient.
A total of 9352 specimens belonging to 41 families were found, and the analysis based on the abundance of polychaete species revealed five affinity groups: (a) nearshore medium sand characterised by Pisione parapari and Hesionura elongata; (b) very coarse sand that showed the highest abundance of Syllidae and was characterised by Protodorvillea kefersteini and Syllis garciai; (c) fine sand dominated by Spiophanes bombyx and Glycera tridactyla; (d) very fine sand with Nepthys assimilis and Amage sp. and the highest abundance of Paraonidae; (d) mud characterised by Labioleanira yhleni and Ampharete finmarchica. The combination of the environmental variables and the biological data, done with BIOENV routine, demonstrated that depth, grain size and fine contents were the best related with the biological data (rho=0.598). In general, the results agree with the composition and the spatial distribution of the polychaete fauna in other parts of the world; further polychaete assemblages related to mud sediments were firstly recorded in the Northwestern Portuguese Coastal Shelf.
35
Pillay, Kerry-Anne. "Diversity and spatial distribution of fungal endophytes in a Eucalyptus grandis tree." Diss., University of Pretoria, 2012. http://hdl.handle.net/2263/31514.
Full textAbstract:
Endophytic fungi of most woody trees are poorly studied due to their cryptic existence, the
complexity of the community and the poor ability of traditional tools to characterize them.
This study characterised the endophytic community present in commercially important
Eucalyptus grandis trees in South Africa. Two different experimental approaches were used.
Firstly environmental bar-coding, or metagenetics, was done using 454-pyrosequencing
parallel sequencing of the barcode amplicons of all the fungal isolates present in the plants
from the total DNA of the plant. Secondly, conventional DNA bar-coding of was done of
fungal endophyte isolates. Isolates of the Botryosphaeriaceae family of latent endophytic
pathogens were further characterised using a multi-gene phylogenetic approach from both
E. grandis and related native S. cordatum that grew in close proximity.
The endophytes within the three E. grandis trees were hyper diverse. A total of 1 281
Molecular Operational Taxonomic Units (MOTU) was identified based on 454-
pyrosequencing of the E. grandis fungal endophyte infections. Only 85 fungal endophytic
species were identified amongst isolates from one of these trees, using the conventional
DNA bar-coding approach. Fifteen times more species/MOTU was thus recovered using a
metagenetics compared to an isolation approach. Despite this high diversity the species
accumulation curves indicate that more endophytic diversity is to be discovered. The multigene
analysis of Botryosphaeriaceae isolates obtained from the E. grandis and S. cordatum
trees show that three species co-infect both these hosts. Two novel host associations are
also reported. This approach of verifying identities of cryptic species with appropriate multigene
analyses is most likely needed for other diverse species complexes associated with
these trees.
A very thorough sampling strategy is required to adequately characterize the endophyte
diversity in trees. The experimental approach, the 454-pyrosequening identification workflow
and database described in this study will be useful to study these endophyte communities
over time and space in future. Using these techniques and workflows described, questions
related to host association, diversity and spatial distribution within hosts, and geographical
delimitation of endophytes can be addressed.Dissertation (MSc)--University of Pretoria, 2012.
Genetics
MSc
Unrestricted
36
Southerland, Megan Amber, and Stevem C. Keitzer. "The Distribution and Diversity of Plethodontid Salamanders in Southern Greene County, Tennessee." Digital Commons @ East Tennessee State University, 2019. https://dc.etsu.edu/asrf/2019/schedule/69.
Full textAbstract:
The salamander diversity in the southern Appalachian Mountains is now being threatened, with lungless salamanders (family Plethodontidae) likely the most vulnerable. Multiple environmental factors threaten Plethodontids, and environmental changes uniquely affect each species within this family. Unfortunately, there is a lack of understanding about the current status of salamanders in Greene County, TN that severely limits conservation efforts for lungless salamanders. This study examined local salamander populations’ current distributions and connected salamander abundance and species richness with a subset of environmental factors to determine what areas represent suitable habitat for different Plethodontids. This information was used to develop species distribution models, which were used to identify potential areas of salamander habitat to focus management and conservation efforts. Area constrained surveys were completed at 42 transects within four main areas using a robust, random sampling design. Abiotic and biotic data, along with salamander identification, were documented at each site. Four additional variables were acquired by geographic information system (GIS 10.6). Salamanders were present at 69% of the transects. Our results indicate that salamanders tend to be located at higher elevations, in ravines, and in thicker canopy cover areas. This work will be useful in long-term monitoring and future research as salamander population, habitat, and environmental changes continue to be monitored.
37
Nunkoo, Muhammad Azher Irfan. "Studies on the diversity and distribution of marine ichthyoparasites in Southern Africa." Doctoral thesis, Faculty of Science, 2019. http://hdl.handle.net/11427/30941.
Full textAbstract:
Parasites are a vital component of ecosystems. However, their contribution to the functioning and structuring of ecosystems has historically been overlooked worldwide. In South Africa, marine ichthyoparasitology has a long history but research has largely been confined to taxonomic studies and the literature pertaining to marine ichthyoparasites is highly fragmented. This situation makes it difficult to gauge advances in marine parasitology, identify knowledge gaps and hampers our understanding of their ecological roles in the marine environments of Southern Africa as well as their use as tools in fisheries science. This thesis aims to explore the diversity of metazoan marine ichthyoparasites reported from Southern African waters and to examine their inter- and intraspecific distribution in marine fishes. A review of two centuries of parasitological literature, 1818 to 2017, revealed that 378 marine ichthyoparasites have been recorded off South Africa and included taxa from six phyla: Acanthocephala (12), Annelida (6), Arthropoda (210), Cnidaria (11), Nematoda (6) and Platyhelminthes (133). The parasites formed 723 unique host-parasite pairs with 269 host taxa spread across the classes Actinopterygii (186), Elasmobranchii (80), Holocephalii (2) and Myxini (1). Host species with the most diverse parasite assemblages were species of commercial significance, namely Thyrsites atun (20) followed by Merluccius capensis (17). The dominance of arthropods and platyhelminthes, which together accounted for 90.7% of the parasites found, reflects the interest and expertise of local and foreign researchers who have worked in South Africa. The parasite assemblage of selected commercially significant fish species was used to assess the degree of interspecific similarity in parasite community structure and identify the drivers of ichthyoparasite community assembly in the Southern Benguela. The examination of 554 specimens comprising six fish species (Brama brama, Chelon richardsonii, Merluccius capensis, Merluccius paradoxus, Sardinops sagax and Thyrsites atun) caught off the South African west coast revealed that they hosted 41 metazoan parasite taxa. These included 10 new host records and five new geographic records. Thyrsites atun and C. richardsonii had the most speciose component communities being infected by 17 and 14 taxa respectively. Multivariate analyses revealed that host habitat and identity in conjunction with the host specificity of ectoparasites influenced the community structure of ectoparasitic assemblages. Larval endoparasite community structure, on the other hand, differed between inshore and offshore habitats. Within the offshore habitat, further variation in endoparasite communities were driven by the host species‘ position in the food web, its trophic ecology and its vulnerability to potential final hosts of larval parasite taxa. A survey of the metazoan parasites of snoek (Thyrsites atun) caught in the Southern Benguela (n = 262) and the Northern Benguela (n = 87) revealed 18 taxa comprising 12 new geographic records for the Northern Benguela. A generalised additive mixed model (GAMM) indicated that infracommunity richness of snoek was determined by host size. Multivariate analyses revealed an ontogenetic shift, driven by an increase in the prevalence and infection intensity of trophically transmitted taxa (Anisakis sp., Corynosoma australe, Hepatoxylon trichiuri, Molicola uncinatus), in infracommunity structure as well as in the long-lived larval parasite assemblage. A ‗Random Forest‘ analysis selected Anisakis sp. and M. uncinatus as potential biological tags for assessing the population structure of snoek in the Benguela ecosystem. GAMMs with binomial and Tweedie error distributions were used to respectively assess the prevalence and abundance of both selected taxa in relation to host traits, seasonality and region of origin. The analyses demonstrated that anisakids were more prevalent and abundant in snoek caught in the Southern Benguela while M. uncinatus were more prevalent in snoek from the Northern Benguela. The spatial differences in infection levels of both parasite taxa suggest the presence of two snoek populations in the Benguela ecosystem. The information collected, collated and presented in this thesis has enabled an assessment of the present state of marine ichthyoparasitology off Southern Africa. Although the work uncovered a diverse ichthyoparasite fauna, it also revealed a bias towards particular parasitic taxa. The study highlighted a need for wide-ranging parasite surveys not restricted to certain host or parasite taxa in order to improve our knowledge of marine ichthyoparasite diversity in South Africa. The thesis also provided the first assessment of the drivers of parasite community assembly in the Southern Benguela and demonstrated that host ecology and the characteristics of the parasites played an important role in determining their distribution and interspecific distribution. Geographic differences in snoek parasite distribution patterns which reflect ecological variations across ecosystems have also proved useful to inform fishery management.
38
Roux, Maryanne. "The diversity and distribution patterns of intertidal fish in the Agulhas bioregion." Thesis, Nelson Mandela Metropolitan University, 2013. http://hdl.handle.net/10948/d1019712.
Full textAbstract:
This study aimed to expand the existing knowledge on the diversity and distribution patterns of intertidal fishes in the Sardinia Bay MPA and adjacent open access areas. It focussed particularly on in intertidal fish communities along the Agulhas Bioregion coast which has been understudied, especially in recent years. Typical resident species belonging to the family Clinidae were the most abundant, conforming to previous studies. Species from the family Gobiidae were the second most abundant in this study but this family was not previously recorded as being abundant. Transient species were unimportant in the current study which is in contrast to previous studies in the region and suggests a change in species composition. Certain transient species utilised intertidal rockpools as part of their nursery areas in the Eastern Cape, as has previously been found around Algoa Bay. A decrease in species richness from east to west was recorded in this study which has been noted by previous authors and the diversity and distribution patterns of the intertidal fish in the current study conformed to patterns found previously. The position of the biogeographic boundary between the Agulhas and Natal Bioregions could not be confirmed but Wavecrest (along the Transkei coastline) appeared to be part of a transition zone rather than a fixed break. More sampling around this area is recommended to determine the location and understand the dynamic nature of this boundary. The fish species were found to be vertically distributed across the shore with most of the resident species being more abundant across the low shore while the transient species were more abundant in the middle to low shore pools. This vertical distribution has been found at many sites around the world. The volume of the pools proved to be the primary controlling factor while the effect of temperature on vertical distribution could not be demonstrated. The benefits of the Sardinia Bay Marine Protected Area on this unexploited community of fishes could not be demonstrated but the long term benefit of protection has yet to be shown. Results from this study suggest that despite the correspondence with general biogeographic trends, the intertidal fish community has changed in composition (at least in terms of transient species) during the last 30 years and the cause for these changes may in part be reduced recruitment from exploited linefish.
39
Slingsby, Michael Timothy. "DNA diversity and meiotic crossover distribution in the Xp/Yp pseudoautosomal region." Thesis, University of Leicester, 2003. http://hdl.handle.net/2381/30350.
Full textAbstract:
High resolution analyses indicate that meiotic crossovers in human autosomes tend to cluster into 1-2 kb hotspots separated by blocks of high LD tens to hundreds of kilobases long. In contrast, low resolution data suggest only modest regional variation in recombination efficiency across the 2.6 Mb Xp/Yp pseudoautosomal region (PAR1), a male-specific recombination hot domain with a recombination rate about twenty times higher than the genome average. Recent data suggest a more complex picture of PAR1 recombination. Around the SHOX gene, 500 kb from the telomere, LD decays extremely rapidly with physical distance, but nearly all crossovers cluster into a highly localised hotspot about 2 kb wide. In contrast, SNPs in a 1.5 kb region immediately adjacent to the PAR1 telomere are in intense LD, implying that this region is recombinationally inert and that male crossover activity terminates at a currently unidentified boundary in the distal region of PAR1. To further investigate PAR1 recombination, the PGPL gene, 80 kb from the telomere, was targeted for analysis. This region had to be sequenced prior to SNP discovery and recombination analysis, revealing a novel gene that is potentially the most telomeric gene in PAR1. SNP analysis of a 33 kb PGPL interval showed that this region is in free association with the telomere, suggesting recombinational activity in the intervening region, which this study proved to be rich in tandem repeats. Within the PGPL region, LD decays slowly with physical distance at a rate consistent with randomly-distributed crossovers occurring at close to the genome average rate. However, sperm crossover analysis revealed it to be the most recombinationally active region of DNA yet identified. Moreover, the novel distribution of crossovers in the region, suggests that there is not a unified set of hotspot-based rules that govern meiotic recombination in the human genome.
40
Waidner, Lisa A. "Abundance, diversity, and distribution of aerobic anoxygenic phototrophic bacteria in the Delaware estuary." Access to citation, abstract and download form provided by ProQuest Information and Learning Company; downloadable PDF file, 219 p, 2007. http://proquest.umi.com/pqdweb?did=1362525071&sid=2&Fmt=2&clientId=8331&RQT=309&VName=PQD.
Full text
41
Khera, Tanya. "The diversity and distribution of Mycobacterium species in varying ecological and climatic environments." Thesis, University of Warwick, 2012. http://wrap.warwick.ac.uk/51639/.
Full textAbstract:
The species within the genus Mycobacterium are commonly detected in a variety of environments including soil, water and dust. Many species within the group are capable of causing opportunistic diseases and are hypothesised to be responsible for the reduction in BCG efficacy in tropical countries. Consequently it is important to understand the diversity and biogeography of mycobacteria in the environment. Soil and water samples were collected from a total of 42 residential sites in 9 different climatic regions. To determine community composition, community DNA was extracted and amplicon pyrosequencing was employed to target the 16S rRNA gene of the Mycobacterium genus and slow-growing mycobacteria. Quantitative PCR was employed to quantify the total abundance of Mycobacterium species and specifically members of the M. tuberculosis complex. The study revealed a greater diversity of both fast-growing and slow-growing mycobacteria than previously reported. Prevalent species in soil were closely related to the fast growers M. neglectum, M. moriokaense and the slow growers M. malmoense and M. colombiense, in contrast to water had a high abundance of sequences related to the fast growers M. aurum sp. ATCC 23070, M. neoaurum and the slow-growers M. gordonae and M. colombiense. The abundance of the Mycobacterium genus ranged from 3.35 x 101 to 8.01 x108 gene copies per gram/ml. M. bovis was detected in six environmental samples using qPCR. Biogeographical analysis demonstrated the importance of elevation and temperature for the community composition of mycobacteria in soil. A nonlinear relationship was observed between elevation and the outcome variables Mycobacterium species richness, diversity and abundance with a peak midelevation. In contrast latitude was the primary factor to explain the composition and diversity of mycobacteria in water samples. To our knowledge this is the first time that the diversity and abundance of mycobacteria has been elucidated on a large geographical scale using pyrosequencing and multivariate analyses. Results indicate ample opportunity for human exposure to mycobacteria with potentially pathogenic species in soil and water substrates. These results have implications for the risk of infection and similar biogeographical surveys on a worldwide scale may provide improved correlations with BCG vaccine efficacy.
42
Van, Rooyen Neil David. "Diversity and distribution of birds in villages in the Kalahari / N.D. van Rooyen." Thesis, North-West University, 2009. http://hdl.handle.net/10394/4379.
Full textAbstract:
Urbanisation and human settlements affects natural habitats in South Africa and around the world through the removal of vegetation, construction of roads and houses, and by various forms of pollution. The Bophirima District of the North West province is a desert margin area - a fragile ecosystem facing the threat of desertification and land degradation. The area has a high diversity of bird species, but is also an area where small villages and human settlements are continuing to modify the natural environment. To determine the effect of urbanisation in a desert margin area, bird surveys were done in three of these settlements. Three habitat types were present at each village - natural, edge, and village habitat. The structure within the villages consisted of unpaved roads, small houses, and several other small buildings. Data was collected in and around the villages by plotting out evenly-spaced point count sites on a 250 x 250 m grid across each village, covering all three habitat types. Bird species were identified, and the number of individuals per species was recorded at each site over four surveys. Surveys were done with the expectation that bird numbers and species richness would be higher within the villages, as predicted by the "intermediate disturbance hypothesis". Bird numbers and species diversity were expected to decrease toward the edges and outskirts of the villages, where the opportunities created by urbanisation were missing. Different guilds were also expected to show different responses to urbanisation and habitat change. Geostatistical analyses, analyses of variance (ANOVA) and an indicator species analysis was performed. The results did indeed indicate that urbanisation increased the overall species richness and number of birds. The reasons for this can be attributed to an increase in additional food and water sources within the villages, as well as the availability of nesting sites, shelter and perches created by buildings, rooftops, poles, fences and other man-made structures. At the edges of the village and in the surrounding habitat, bird numbers and species diversity were often significantly lower, probably due to the absence of these man-made structures and anthropogenic resources. In terms of feeding guilds, an increase in granivores was observed within the villages, while insectivores and carnivores showed higher abundances in the natural habitats. Nesting guilds which responded positively to urbanisation were tree- and structure-nesters, while ground- and shrub-nesters preferred the natural habitats. It was concluded that bird distribution was very much affected by areas where their food and nesting requirements could best be fulfilled. In a desert margin area, where avian diversity is currently threatened by global warming and land degradation, these villages could serve as important conservation sites for birds. Several questions still need to be answered through future research, but it is recommended that proper management strategies and sustainable development plans are implemented to ensure the maintenance of species richness and bird numbers in such villages.Thesis (M.Sc. (Environmental Science))--North-West University, Potchefstroom Campus, 2010.
43
Gelbard, Jonathan L. "Understanding the distribution of native versus exotic plant diversity in California's grassland landscapes /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2003. http://uclibs.org/PID/11984.
Full text
44
Wallis, Kirsty K. "Investigating the ecology, diversity and distribution of cord-forming fungi in Great Britain." Thesis, University of Oxford, 2014. http://ora.ox.ac.uk/objects/uuid:d7de00b0-74fa-473b-ac6a-c3ae61f6ac27.
Full textAbstract:
Cord-forming fungi (CFF) are an assemblage of saprotrophic fungi which can use complex foraging organs of longitudinally arranged hyphae to join up disparate substrates in a patchy resource environment. Their importance to woodlands lies, mainly, in their ability to modify nutrient cycling and soil structure. Therefore, in order to enable woodlands to continue to thrive in terms of their health and ecosystem function, it is necessary to understand the factors contributing to the establishment, success and diversity of this group. Whilst work to date on CFF has focussed on their physiology and interactions in laboratory conditions, little work has been carried out on their taxonomy and establishment/presence in the field. The work in this thesis begins to address these crucial unanswered questions in CFF ecology. By carrying out investigations at a range of scales, from phylogenetic analysis to UK wide Species Distribution Modelling, this thesis reaches a number of surprising results with potentially important implications for woodland management. This is most evident in Chapter 3 where our hypothesis that fungal communities develop over time in plantations of different woodland ages was disproved, illustrating that even 13 years after planting, fungal communities in plantations on ex-agricultural land had not begun to reach those in established ASNW. These unexpected results continue into Chapter 4, where the thesis demonstrates that dominant canopy species has a greater impact on community composition than any other woodland factor. Chapter 5 continues this theme, by showing that removal of invasive species is not always beneficial for the cord-forming fungal communities, especially if it involves removing the woody substrate. The work described, detailed and analysed in this thesis has initiated further investigations, proposed changes to woodland management practices and laid the foundations for future work relating to CFF and their role and function in British woodlands.
45
Taylor, Michelle Lisa. "Distribution and diversity of octocorals from longline by-catch around South Georgia, UK." Thesis, Imperial College London, 2012. http://hdl.handle.net/10044/1/9221.
Full textAbstract:
In recent decades man’s forays into the deep sea have been increasingly frequent and wide-reaching; the most immediately intense and widespread activity being fisheries. United Nations (UN) General Assembly Resolutions on Sustainable Fishing on the High Seas call for assessment of fishing impacts with the aim of helping fisheries to avoid damaging vulnerable marine ecosystems. Octocorals form the majority of by-catch in the bottom-longline fishery for Patagonian toothfish, Dissostichus eleginoides Smitt, 1898, around South Georgia. I employed several methods to investigate octocoral extent, location and diversity using by-catch from this fishery. Preliminary video analysis from camera arrays attached to bottom-longlines found whip corals interacted with longlines less than bushy, fanshaped corals or Stylasteridae. Stylasteridae were however very fragile with 42% of interactions likely resulting in mortality through dislodgement. Deep-sea octocorals are relatively understudied with many families and genera requiring revision and, as such, morphologically identifying octocorals is a difficult task; I thus investigated by-catch diversity by embedding octocorals caught from this South Georgia fishery into a wider Octocorallia phylogenetic tree. Three polyphyletic groups were resolved. Putative species numbers were estimated from morphological and phylogenetic analysis. Morphological identifications of one family of octocorals, Primnoidae, were compared to phylogenetic trees and the probability species were monophyletic tested using the statistical programme, Species Delimitation for Geneious. Six families, at least 21 genera (including three new discoveries) composing of a minimum of 34 species were caught as by-catch. Thouarella Gray, 1870, was the most common genus caught and a revision of this genus is presented. Using recently created fine scale (150 m by 150 m) bathymetry of South Georgia, a depth-derived megahabitat map was created and octocoral occurrence data used to predict octocoral habitat suitability. Shelf troughs, crest and slope areas were highlighted as highly suitable octocoral habitat which substantially overlaps fishing areas. Current management protection regulations were found to protect highly suitable octocoral habitat.
46
Großmann, Lars [Verfasser], and Jens [Akademischer Betreuer] Boenigk. "Diversity of protists with special emphasis on chrysomonads : morphological and molecular diversity, distribution patterns and functional differentiation / Lars Großmann ; Betreuer: Jens Boenigk." Duisburg, 2016. http://d-nb.info/1122018851/34.
Full text
47
Geleta, Mulatu. "Genetic diversity, phylogenetics and molecular systematics of Guizotia Cass. (Asteraceae) /." Alnarp : Department of Plant Protection Biology, Swedish University of Agricultural Sciences, 2007. http://epsilon.slu.se/200727.pdf.
Full text
48
Geisen, Stefan [Verfasser], Michael [Akademischer Betreuer] Bonkowski, and Hartmut [Akademischer Betreuer] Arndt. "Soil Protists Diversity, Distribution and Ecological Functioning / Stefan Geisen. Gutachter: Michael Bonkowski ; Hartmut Arndt." Köln : Universitäts- und Stadtbibliothek Köln, 2014. http://d-nb.info/1068619759/34.
Full text
49
Compte, Port Sergi. "Factors affecting the distribution, abundance and diversity of uncultured archaeal groups in freshwater sediments." Doctoral thesis, Universitat de Girona, 2018. http://hdl.handle.net/10803/663927.
Full textAbstract:
Archaea are abundant in extreme environments but they are also a prevalent component of microbial communities in soils, marine or freshwater plankton and sediments. Many studies highlighted the prominent role of marine sedimentary Archaea in global nutrient cycles. Less information is available, however, on the diversity, abundance and ecological role of Archaea in freshwater sediments. A serious pitfall for the study of Archaea is their low cultivability under laboratory-controlled conditions thus constraining the progress towards the complete understanding of their metabolic capabilities and ecological functions. Most of the work is thus based on molecular techniques that allow the identification and quantification of target microorganisms without their cultivation. In this PhD project, we applied a combination of high-throughput sequencing and quantitative PCR to investigate the distribution, abundance and composition of archaeal communities in sediments from different freshwater systems (lakes, lagoons and reservoirs encompassing a wide range of conditions and typologies). The work has been focused in two archaeal groups consistently found, and especially abundant, in sediments: the phylum Bathyarchaeota and the class ThermoplasmataEls arqueus abunden en ambients extrems però també són un component rellevant dels sòls, del plàncton oceànic i lacustre i dels sediments. Molts estudis han destacat la importància dels arqueus en els cicles de nutrients dels sediments marins tant a escala local com global. En canvi, es disposa de menys informació sobre la diversitat, abundància i paper que juguen els arqueus en sediments d’aigua dolça a excepció dels metanògens. Com a dificultat afegida, la majoria d’arqueus sedimentaris no s’han pogut cultivar encara al laboratori, el que dificulta el seu estudi. La solució a aquests problemes passa per l’aplicació de tècniques moleculars que permeten la identificació i recompte dels microorganismes diana sense necessitat de cultivar-los. En aquesta tesi s’han combinat diferents tècniques moleculars (seqüenciació massiva i PCR quantitativa) per a conèixer la distribució, abundància i composició de les comunitats d’arqueus en sediments de sistemes aquàtics d’aigua dolça (llacs, llacunes i embassaments amb diferents condicions i tipologies). La tesi s’ha centrat en dos grups d’arqueus que són ubics i especialment abundants en sediments: el fílum Bathyarchaeota i la classe Thermoplasmata
50
Zayas, Ena Edith Mata. "The distribution of phylogenetic diversity of mammals in Mexico and its implications for conservation." Thesis, University of Plymouth, 2007. http://hdl.handle.net/10026.1/2342.
Full textAbstract:
The current rate of biodiversity loss has stimulated studies aimed at identifying areas of concentration of biodiversity where conservation efforts can be targeted. Phylogeny has become an important element in conservation either to preserve areas of high phylogenetic diversity (and therefore evolutionary history) or to identify species attributes that make them prone to become endangered or at risk of extinction. This dissertation dealt with the quantification of phylogenetic diversity of Mexican mammals, its geographic distribution, and its correlation with both the life history attributes of the species and selected characteristics of the environment. In order to do this, I had to construct a complete and reasonably well-resolved phylogeny of the 416 species of terrestrial mammals. This has allowed assessing the benefits and limitations, as well as the similarities and differences, of the two indices of phylogenetic information currently in use: Faith's index of phylogenetic diversity (PD) and Clarke & Warwick's index of taxonomic distinctiveness (TD). This has also allowing to evaluate the degree of correspondence between the distribution of these indices and the distribution of the natural protected areas of Mexico and to identify the minimum number of reserves (and their location) that would be required to protect all 416 species. Although these indices show a high degree of correlation, by emphasising slightly different aspects of the topology of the classification, they sometimes differ in their identification of priority areas. The results show that the value of either PD or TD is determined primarily by species-richness (S) and secondarily by the topology of the phylogeny. In general, areas of high phylogenetic complexity (HPA, those made up of distantly-related taxa, independent of their number) are found mainly in regions traditionally recognised as worthy of conservation, such as the Transvolcanic Belt and the tropical South-East region. Comparative analysis employing the method of independent contrasts showed the correlation between different life history attributes of the species, as well as the correlation between these life history attributes and some characteristics of the environment (such as latitudinal range, average temperature and average precipitation in the distribution of each species). This permitted exploration of the benefits and limitations of life histories as subjects for conservation.