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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Spatial and Temporal Patterns of Diversification in Leaf-toed Geckos (Phyllodactylidae: Phyllodactylus) throughout the Mexican Dry Forest

Blair, Christopher 10 December 2012 (has links)
Understanding the ecological and evolutionary processes responsible for shaping patterns of genetic variation in natural populations is a long-standing goal in molecular ecology. Although an extensive number of recent studies focus on patterns and processes throughout tropical rain forest ecosystems, substantially less effort has been placed on tropical dry forests (TDFs); a habitat known to harbour a large percentage of Earth’s diversity. In this thesis I use leaf-toed geckos of the genus Phyllodactylus to understand both the historical and contemporary processes influencing diversification throughout Mexico’s TDFs. In Chapter 2 I isolate and characterize microsatellite markers for the gecko P. tuberculosus. Chapter 3 uses these loci to conduct a landscape genetic analysis of the species near Alamos, Sonora. I find that the inclusion of landscape variables explains more genetic variance versus Euclidean distance alone. Chapter 4 examines the evolutionary history of the P. tuberculosus group throughout western Mexico. Results suggest that habitat and climate shifts during the Miocene and Pleistocene were important divers of diversification. Chapter 5 uses microsatellite and mtDNA markers to compare historical and contemporary demographic parameters in P. tuberculosus. I find evidence for low historical gene flow and high female philopatry, recent reductions in population sizes, and higher correlations between landscape and contemporary gene flow versus historical gene flow and mtDNA divergence. In Chapter 6 I examine the biogeographic and taxonomic consequences of the dynamic history of Baja California. My phylogenetic results provide evidence for a trans-peninsular seaway in the Isthmus of La Paz region and suggests that P. xanti nocticolus warrants species status. My results also suggest the possibility of a seaway near the Loreto area that needs to be evaluated further. By combining multiple molecular marker-types and analytical methods, this thesis adds to our understanding of diversification processes throughout the threatened Mexican TDF.
42

Phylogenetic Relationships among the Scolopaci (Aves: Charadriiformes): Implications for the Study of Behavioural Evolution

Gibson, Rosemary 06 April 2010 (has links)
Unraveling the relationships between organisms and patterns of diversity is a central goal of evolutionary biology, pursuant to the aim of reconstructing the history of life. I constructed a hypothesis for species relationships in the shorebird suborder Scolopaci, and mapped onto this framework behavioural and life-history traits to infer their evolutionary history. Relationships were well-resolved and well-supported, although reliable resolution of certain nodes will require additional, independent sources of information. We estimated the Scolopaci ancestor to be monogamous, and care-giving through fledging, but ancestral breeding location and migration distance reconstructions were equivocal. Tests for correlations between parental care and other traits to explain extant species’ trait diversity show that, contrary to previous reports, evolution of Scolopaci diversity was a complex process that cannot be explained by individual character correlations. This study provides important insights into Scolopaci and shorebird evolutionary history, and the general practice of inferring past processes from phylogenetic hypotheses.
43

Above and Below Ground Fungal Diversity in a Hemlock-dominated Forest Plot in Southern Ontario and the Phylogenetic Placement of a New Ascomycota Subphylum

McLenon-Porter, Teresita Mae 01 August 2008 (has links)
The objective of this thesis was to assess the diversity and community structure of fungi in a forest plot in Ontario using a variety of field sampling and analytical methods. Three broad questions were addressed: 1) How do different measures affect the resulting view of fungal diversity? 2) Do fruiting bodies and soil rDNA sampling detect the same phylogenetic and ecological groups of Agaricomycotina? 3) Will additional rDNA sampling resolve the phylogenetic position of unclassified fungal sequences recovered from environmental sampling? Generally, richness, abundance, and phylogenetic diversity (PD) correspond and identify the same dominant fungal groups in the study site, although in different proportions. Clades with longer branch lengths tend to comprise a larger proportion of diversity when assessed using PD. Three phylogenetic-based comparisons were found to be variable in their ability to detect significant differences. Generally, the Unifrac significance measure (Lozupone et al., 2006) is the most conservative, followed by the P-test (Martin, 2002), and Libshuff library comparison (Singleton et al., 2001) with our dataset. Fruiting body collections and rDNA sampling recover largely different assemblages of fungi at the species level; however, both methods identify the same taxonomic groups at the genus-order level as well as ectomycorrhizal fungi as the dominant functional type of Agaricomycotina. This work also shows that the Soil Clone Group I (SCGI) clade is widespread in soils of diverse origins and represents a novel subphylum of Ascomycota.
44

Phylogenetic Relationships among the Scolopaci (Aves: Charadriiformes): Implications for the Study of Behavioural Evolution

Gibson, Rosemary 06 April 2010 (has links)
Unraveling the relationships between organisms and patterns of diversity is a central goal of evolutionary biology, pursuant to the aim of reconstructing the history of life. I constructed a hypothesis for species relationships in the shorebird suborder Scolopaci, and mapped onto this framework behavioural and life-history traits to infer their evolutionary history. Relationships were well-resolved and well-supported, although reliable resolution of certain nodes will require additional, independent sources of information. We estimated the Scolopaci ancestor to be monogamous, and care-giving through fledging, but ancestral breeding location and migration distance reconstructions were equivocal. Tests for correlations between parental care and other traits to explain extant species’ trait diversity show that, contrary to previous reports, evolution of Scolopaci diversity was a complex process that cannot be explained by individual character correlations. This study provides important insights into Scolopaci and shorebird evolutionary history, and the general practice of inferring past processes from phylogenetic hypotheses.
45

Community phylogenetics: methodological approaches and patterns in subarctic freshwater insect systems

Boyle, Elizabeth 03 October 2012 (has links)
I aimed to expand our understanding of community assembly and species co-existence by examining the implications of phylogenetic robustness on metrics describing phylogenetic community structure, as well as the phylogenetic patterns of co-occurring insect species in Churchill, MB. Using a variety of tree reconstruction methods, I found that cytochrome c oxidase subunit I (COI) was able to accurately estimate phylogenetic community structure metrics calculated from a multi-gene phylogeny when using more biologically realistic approaches. This included incorporating known phylogenetic relationships among families, and methods that employ best-fit models of molecular evolution (i.e. Bayesian inference). My second study examined the phylogenetic community patterns of freshwater insects. Overall communities were phylogenetically clustered suggesting environmental filtering, but community structure varied with time, habitat, taxonomic group, and water chemistry (particularly pH and turbidity). My thesis has suggested more robust techniques for calculating phylogenetic community structure, and described patterns of phylogenetic community composition in subarctic freshwater insects. / Natural Sciences and Engineering Research Council of Canada (NSERC), International Barcode of Life (iBOL), Genome Canada, Ontario Genomics Institute, Canadian Foundation for Innovation, Ontario Ministry of Research and Innovation, Churchill Northern Studies Centre, and Aboriginal Affairs and Northern Development Canada.
46

Above and Below Ground Fungal Diversity in a Hemlock-dominated Forest Plot in Southern Ontario and the Phylogenetic Placement of a New Ascomycota Subphylum

McLenon-Porter, Teresita Mae 01 August 2008 (has links)
The objective of this thesis was to assess the diversity and community structure of fungi in a forest plot in Ontario using a variety of field sampling and analytical methods. Three broad questions were addressed: 1) How do different measures affect the resulting view of fungal diversity? 2) Do fruiting bodies and soil rDNA sampling detect the same phylogenetic and ecological groups of Agaricomycotina? 3) Will additional rDNA sampling resolve the phylogenetic position of unclassified fungal sequences recovered from environmental sampling? Generally, richness, abundance, and phylogenetic diversity (PD) correspond and identify the same dominant fungal groups in the study site, although in different proportions. Clades with longer branch lengths tend to comprise a larger proportion of diversity when assessed using PD. Three phylogenetic-based comparisons were found to be variable in their ability to detect significant differences. Generally, the Unifrac significance measure (Lozupone et al., 2006) is the most conservative, followed by the P-test (Martin, 2002), and Libshuff library comparison (Singleton et al., 2001) with our dataset. Fruiting body collections and rDNA sampling recover largely different assemblages of fungi at the species level; however, both methods identify the same taxonomic groups at the genus-order level as well as ectomycorrhizal fungi as the dominant functional type of Agaricomycotina. This work also shows that the Soil Clone Group I (SCGI) clade is widespread in soils of diverse origins and represents a novel subphylum of Ascomycota.
47

An investigation of the symbiotic association between the sub-aquatic fungus Dermatocarpon luridum var. luridum and its green algal photobiont

Fontaine, Kyle Matthew 10 October 2012 (has links)
The biology of the sub-aquatic lichen, Dermatocarpon luridum, was investigated. This lichen is sparsely distributed within the temperate climatic zones around the world, colonizing rock along watercourses that regularly experience water level fluctuations. Specimens collected from Canada and Austria were cultured using standard growth media. Brightfield microscopy was used for algal species identification, while fungal ITS, algal ITS and algal actin gene sequences were used for phylogenetic and population genetic evaluation. Results were: 1) axenic cultures of the photobiont were successful, while those of the mycobiont were not successful; 2) Diplosphaera chodatii is the photobiont associated with D. luridum var. luridum and allies, suggesting algal sharing between mycobiont species; 3) genetic diversity is high, and gene flow was high within local populations, but low between continental populations. Diplosphaera chodatii may be a keystone species contributing to the survival of D. luridum var. luridum along with other sub-aquatic, aquatic and terrestrial lichens.
48

Phylogenetics and molecular identification of the Ochlerotatus communis and Oc. punctor complexes (Diptera: Culicidae)

Hosseinzadeh Namin, Hooman 10 September 2013 (has links)
Accurate identification of pathogens and vectors is essential in epidemiological studies of mosquito-borne pathogens. However, the members of the communis and punctor complexes are difficult to distinguish because they are highly cryptic species, with little to no species-specific morphological characters. The objective of this thesis is to develop molecular tools, including RFLP and DNA barcoding using cytochrome oxidase I (COI), internal transcribed spacer 2 (ITS2) and the intron of ribosomal protein S12 (RPS12) to facilitate identification of the members of these two complexes in Manitoba. A distinct interspecific distance for COI was found between the members of the communis complex included here, and diagnostic RFLP profiles were developed for Oc. communis and Oc. churchillensis. Relatively low average interspecific genetic distances using COI, ITS2 and RPS12 were observed between the members of the punctor complex, indicates no discernable boundaries between these species based on DNA barcoding.
49

Studies of phylogenetic relationships and evolution of functional traits in diatoms

Nakov, Teofil 25 June 2014 (has links)
The research presented here deals with inferring phylogenetic trees and their use to study the evolution of functional traits in diatoms (Heterokontophyta: Bacillariophyceae). Two chapters are concerned with the phylogeny of a mainly freshwater group, the Cymbellales, with a convoluted taxonomic history and classification. I generated a multi-gene dataset to test the monophyly of the Cymbellales and reconstruct the relationships within the order. The molecular data were equivocal with respect to the monophyly of the Cymbellales, especially when taking into account some problematic taxa like Cocconeis and Rhoicosphenia. Aside from the problem with their monophyly, my work shows that the current genus- and family-level classification of the Cymbellales is unnatural, arguing for the need of nearly wholesale re-classification of the group. The two following chapters make use of phylogenetic trees to model the evolution of functional traits. I explored the evolution of cell size across the salinity gradient finding that the opposing selective forces exerted by marine and fresh waters select for different optimal cell sizes -- larger in the oceans and smaller in lakes and rivers. Thereafter, I modelled the evolutionary histories of habitat preference (planktonic-benthic) and growth form (solitary-colonial) across the diatoms. These traits exhibit markedly different evolutionary histories. Habitat preference evolves slowly, is conserved at the level of large clades, and its evolution is generally uniform across the tree. Growth form, on the other hand, has a more dynamic evolutionary history with frequent transitions between the solitary and colonial growth forms and rates of evolution that vary through time. I hope that these empirical studies represent an incremental advancement to the understanding of the evolution diatom species and functional diversity. / text
50

Multigene datasets for deep phylogeny

Jones, Martin January 2007 (has links)
Though molecular phylogenetics has been very successful in reconstructing the evolutionary history of species, some phylogenies, particularly those involving ancient events, have proven difficult to resolve. One approach to improving the resolution of deep phylogenies is to increase the amount of data by including multiple genes assembled from public sequence databases. Using modern phylogenetic methods and abundant computing power, the vast amount of sequence data available in public databases can be brought to bear on difficult phylogenetic problems. In this thesis I outline the motivation for assembling large multigene datasets and lay out the obstacles associated with doing so. I discuss the various methods by which these obstacles can be overcome and describe a bioinformatics solution, TaxMan, that can be used to rapidly assemble very large datasets of aligned genes in a largely automated fashion. I also explain the design and features of TaxMan from a biological standpoint and present the results of benchmarking studies. I illustrate the use of TaxMan to assemble large multigene datasets for two groups of taxa – the subphylum Chelicerata and the superphylum Lophotrochozoa. Chelicerata is a diverse group of arthropods with an uncertain phylogeny. When a set of mitochondrial genes is used to analyse the relationships between the chelicerate orders, the conclusions are highly dependent upon the evolutionary model used and are affected by the presence of systematic compsitional bias in mitochondrial genomes. Lophotrochozoa is a recently-proposed group of protostome phyla. A number of distinct phylogenetic hypotheses concerning the relationships between lophotrochozoan phyla have been proposed. I compare the phylogenetic conclusions given by analysis of nuclear and mitochondrial protein-coding and rRNA genes to evaluate support for some of these hypotheses.

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