Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 27 for “"divergence time"”.
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Molecular evolution of beta (â) keratins in three bird species and divergence time estimates for the avian â-keratin subfamilies
… been published and through the knowledge of divergence times and molecular differences between these birds, a better understanding of â-keratin evolution can be achieved and applied to the study of feather evolution. It has been found that tandem arrays of â-keratins reside on several …
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The origins and maintenance of species boundaries in Jamesbrittenia O. Kuntze (Scrophulariaceae: Manuleae)
… and nuclear (GScp) sequence data. Relative divergence times were calculated using a relaxed clock method. Prezygotic isolation, measured as seed set resulting from interspecific crosses, correlated with divergence time. However, recently diverged, highly sympatric taxa deviated from the …
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Patterns of Archaic Hominin DNA in Modern Human Genomes
… from an unknown archaic hominin with an apparent divergence time with modern humans that is similar to the divergence time of Neanderthals. In a sample of 379 European and 279 East Asian genomes, I identify on average 1/4 of each individual's introgressed Neanderthal sequence, composing a total of …
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The path prediction of cyclones with Kalman filters
… the performance of the filter and cause tracking divergence. Time varying values for the noise covariance matricies R and Q, and the addition of an external forcing function to the filter, effectively compensated for this tracking error. Results for the simulations show significant performance …
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Comparative Population Genomics and Speciation of Snakes Across the North American Deserts
… by identifying regions that promote lineage divergence, addressing whether speciation has occurred with gene flow, and when extended to multiple taxa, addressing if the same patterns of speciation are shared across codistributed groups with different ecologies. Here I examine the comparative …
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Phylogeography of the Malagasy Ant Species Otontomachus coquereli
… to relate the complex geography to genetic divergence, and thereby speciation. I explore three hypotheses concerning the effect of mountains, rivers, and watersheds on the genetic distribution of the endemic Malagasy ant species Odontomachus coquereli. I recovered three genetic clusters from …
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Morphometric Characterization of a <i>Mercenaria</i> spp. (Bivalvia) Hybrid Zone: Paleontological and Evolutionary Implications
… in morphological intermediates at ecological time scales (dimorphism, ecophenotypy, and geographic variation). Four alternative causal explanations of morphological intermediates through geological time (primary intergradation, uncoupled genetic and morphological divergence, time-averaged …
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Phylogenetic utility of mitochondrial and nuclear genes: a case study in the diptera (true flies)
… groupings in need of further analysis. For divergence time estimation, we show widespread convergence of clade age estimates from both mitochondrial and nuclear gene sources under a wide variety of data preparation and model paradigms. Our results indicate slightly superior performance of …
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Total evidence phylogeny of ducks, geese and swans(family Anatidae): implications for macroevolution andbiogeography
… a Bayesian approach, with the latterresulting in divergence time estimates that indicate that crown-clade Anatidae originated in the Early Miocene about 19 Ma (95% HPD 14.8-29.0 Ma). The undated and dated total evidence topologies were also used to reconstruct the evolution ofselected …
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The Influence of Structural Constraints on Protein Evolution
… models on simulatedand empirical data for divergence time estimation, tree inference, side chain configurationprediction and ancestral sequence reconstruction.Further, encoding observed characters in an alignment as ambiguous representations ofcharacters in a larger state-space allows the …
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The Evolutionary History of the Antarctic Flora
… Applying population genetic, phylogeographic and divergence time analyses I assessed the global biogeography, origin and age of several abundant Antarctic moss species, including: four Polytrichaceae mosses, characterised by having bipolar distributions, the most common (~45% of species) …
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Biogeochemical and phylogenetic signals of Proterozoic and Phanerozoic microbial metabolisms
… or nonspecific record on geologic timescales. This thesis develops and employs novel geochemical and genetic approaches to illuminate diagnostic signals of microbial metabolisms. Field studies, laboratory cultures, and computational models explain how methanogens produce unique …
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Population genetics and systematics of a species-rich clade of Neotropical reef fishes, the tubeblenny genus Acanthemblemaria
… an absolute rate of nearly 25% pairwise sequence divergence per million years. Replicate Bayesian phylogenetic analyses failed to converge on the same posterior distributions because proposals to update the rate multiplier parameter were rarely accepted, but when the tuning parameter was adjusted, …
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Systematics and Evolution of the Basal Lineages of Therevidae (Insecta: Diptera)
… (with the exclusion of the Phycinae). A divergence time estimate suggested that the basal radiation of the Therevidae was during the time of the Gondwana breakup.
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Distribution and phylogenetic inference within the flightless spring katydids (Tettigoniidae: Brinckiella Chopard, 1955) in the Greater Cape Floristic Region
… and elucidate the phylogenetic relationship and divergence time within the genus. Specimens were collected by hand and sweep netting. Phylogenetic inference was done using the COI gene and analysed under Maximum likelihood and Bayesian inference. This study identified 13 morphospecies of …
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Biogeochemical and phylogenetic signals of Proterozoic and Phanerozoic microbial metabolisms
… or nonspecific record on geologic timescales. This thesis develops and employs novel geochemical and genetic approaches to illuminate diagnostic signals of microbial metabolisms. Field studies, laboratory cultures, and computational models explain how methanogens produce unique …
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Biogeography and phylogenetics of grassland auchenorrhyncha
… infer biogeographic patterns and to estimate divergence times. Grass feeding in Deltocephalini was inferred to be Palearctic in origin, and Old World origins were inferred for each target lineage. Hecalini and Paralimnini were inferred to be Palearctic in origin, while Deltocephalini + …
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Multi-locus phylogenetic inference of the howler monkey (Alouatta) radiation in South America.
… from those proposed in previous studies, the divergence time estimation analyses recovered similar dates to other investigations. The age of the genus <em>Alouatta </em>was estimated at ca. 6.1 Mya (95% Highest Posterior Density, or HPD = 5.2 - 6.9 Mya). The Meso-American clade containing …
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Hybridization in Ants
… the eight ant genomes that were available at the time and designed primers for PCR amplification. Among these loci, I chose 24 for in-depth study in six species covering six different ant subfamilies. On average, 11.16 of these 24 loci were polymorphic and in Hardy-Weinberg equilibrium in any …
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Systematics and biogeography of leafhoppers in Madagascar
… of these lineages were then used to estimate divergence times in order to test different biogeographic hypotheses and determine the most likely scenario(s) for the origin of the Malagasy leafhopper fauna. The species of two widely distributed leafhopper groups in Madagascar, the endemic …
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