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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.
1

Phylogenetic analysis of Pristimantis Jiménez de la Espada, 1870, a megadiverse genus of amphibians (Anura, Brachycephaloidea, Craugastoridae) / Análise filogenética de Pristimantis Jiménez de la Espada, 1870, um gênero megadiverso de anfíbios (Anura, Brachycephaloidea, Craugastoridae)

Rocha, Mariane Targino 28 November 2016 (has links)
The genus Pristimantis has 500 species of anurans with distribution in northwest South America, specially in the Andes. Due to the large number of species morphologically diverse, the genus was divided in 11 species groups, with 312 species not allocated in any of them. The great number of species not allocated in species groups is due to the lack of morphological characters to better define and diagnose these groups, and because most of the anteriorly recognized groups in the literature of 70, 80 and 90s decades of the last century were not recovered monophyletic in the most recent phylogenetic analyses. The present study aims to perform a phylogenetic analysis of Pristimantis, with phenotypic and genotypic characters, through total evidence with dynamic homology and parsimony. As a result, Pristimantis is not monophyletic and some of its species were reallocated in the genus Tachiramantis. The species groups within Pristimantis were reformulated with proposed diagnosis. In total, 25 species groups are here defined / O gênero Pristimantis possui 500 espécies de anfíbios anuros com distribuição no noroeste da América do Sul, concentrado principalmente nos Andes. Devido ao grande número de espécies, morfologicamente diversas, o gênero encontra-se atualmente dividido em 11 grupos de espécies, com 312 espécies não alocadas em grupos. O grande número de espécies não alocadas em grupos se deve especialmente pela falta de dados morfológicos para definir e diagnosticar esses grupos, e pelo fato dos grupos anteriormente reconhecidos nas décadas de 70, 80 e 90, serem em sua grande maioria não monofiléticos. O presente trabalho tem como objetivo uma análise filogenética do gênero Pristimantis, utilizando caracteres fenotípicos e genotípicos através de uma análise de evidência total utilizando homologia dinâmina e parcimônia. Pristimantis não resultou monofilético e algumas de suas espécies foram realocadas no gênero Tachiramantis. Os grupos de espécies em Pristimantis foram reformulados com diagnoses propostas. No total 25 grupos de espécies são reconhecidos
2

Phylogenetic analysis of Pristimantis Jiménez de la Espada, 1870, a megadiverse genus of amphibians (Anura, Brachycephaloidea, Craugastoridae) / Análise filogenética de Pristimantis Jiménez de la Espada, 1870, um gênero megadiverso de anfíbios (Anura, Brachycephaloidea, Craugastoridae)

Mariane Targino Rocha 28 November 2016 (has links)
The genus Pristimantis has 500 species of anurans with distribution in northwest South America, specially in the Andes. Due to the large number of species morphologically diverse, the genus was divided in 11 species groups, with 312 species not allocated in any of them. The great number of species not allocated in species groups is due to the lack of morphological characters to better define and diagnose these groups, and because most of the anteriorly recognized groups in the literature of 70, 80 and 90s decades of the last century were not recovered monophyletic in the most recent phylogenetic analyses. The present study aims to perform a phylogenetic analysis of Pristimantis, with phenotypic and genotypic characters, through total evidence with dynamic homology and parsimony. As a result, Pristimantis is not monophyletic and some of its species were reallocated in the genus Tachiramantis. The species groups within Pristimantis were reformulated with proposed diagnosis. In total, 25 species groups are here defined / O gênero Pristimantis possui 500 espécies de anfíbios anuros com distribuição no noroeste da América do Sul, concentrado principalmente nos Andes. Devido ao grande número de espécies, morfologicamente diversas, o gênero encontra-se atualmente dividido em 11 grupos de espécies, com 312 espécies não alocadas em grupos. O grande número de espécies não alocadas em grupos se deve especialmente pela falta de dados morfológicos para definir e diagnosticar esses grupos, e pelo fato dos grupos anteriormente reconhecidos nas décadas de 70, 80 e 90, serem em sua grande maioria não monofiléticos. O presente trabalho tem como objetivo uma análise filogenética do gênero Pristimantis, utilizando caracteres fenotípicos e genotípicos através de uma análise de evidência total utilizando homologia dinâmina e parcimônia. Pristimantis não resultou monofilético e algumas de suas espécies foram realocadas no gênero Tachiramantis. Os grupos de espécies em Pristimantis foram reformulados com diagnoses propostas. No total 25 grupos de espécies são reconhecidos
3

Cryptic diversity, landscape genetics and diversification in the Pristimantis w-nigram species complex

Kieswetter, Charles M. January 2012 (has links)
Thesis (Ph.D.)--Boston University / PLEASE NOTE: Boston University Libraries did not receive an Authorization To Manage form for this thesis or dissertation. It is therefore not openly accessible, though it may be available by request. If you are the author or principal advisor of this work and would like to request open access for it, please contact us at open-help@bu.edu. Thank you. / Neotropical montane forests of the Ecuadorian Andes harbor a disproportionate amount of global biodiversity, yet the ecological and evolutionary processes that generate and sustain this diversity are poorly known. Determining the relative roles of historical vicariance, natural selection and genetic drift in generating diversity are active areas of investigation, but no clear pattern has emerged. My research focuses on a direct developing cloud forest frog ( Pristimantis w-nigrum ) found along the Eastern and Western versants of the Ecuadorian Andes. By integrating morphological data, multi-locus sequence data and geographic and environmental data, I demonstrate that: (1) Pristimantis w-nigrum harbors substantial genetic diversity, despite morphological stasis, and may comprise a species complex; (2) Genetic differentiation of mitochondrial DNA identifies eight divergent lineages and highly structured populations along both eastern and western slopes of the Ecuadorian Andes; (3) Multiple nuclear markers show lesser but still substantial population structure; (4) Isolation by distance best explains the pattern of genetic variation, but temperature and precipitation also contribute to genetic and morphological variation; (5) The timing of genetic divergence among mtDNA lineages coincides with sequential paleogeological bouts of Andean orogenesis during the late Miocene and early Pliocene, with terminal lineages diverging during the Pleistocene; (6) Populations have experienced little or no gene flow. (7) Those on the Western slope have maintained large effective population sizes, while populations on the Eastern slope appear to have suffered severe bottlenecks. Taken together, these results suggest a long sequential history of vicariance following the orogeny of the Northern Andes and that allopatric speciation may be a common mode of divergence in montane ectothermic vertebrates with low vagility. In addition, estimation of the species phylogeny and historical and contemporary demographic parameters using multiple loci highlight the utility of a multi-locus approach, particularly in cases where diversification may have occurred relatively recently. The identification of cryptic diversity in the P. w-nigrum suggests that evolutionary processes of isolation and divergence are occurring in the Andes and that the Andes may be an important generator of new species as well as a repository of high biodiversity. / 2031-01-01
4

Species Limits, and Evolutionary History of Glassfrogs

Castroviejo-Fisher, Santiago January 2009 (has links)
Recognizing the mechanisms of speciation and the limits of species is essential to understand the origin of biodiversity and how to conserve it. The general aims of my investigations during my doctoral studies were two-fold: to study evolutionary patterns and processes, and to provide specific and superspecific taxonomic classifications that try to reflect evolutionary history. I have focused my research on anurans in their biodiversity hotspot, the American Tropics. I have used morphological, behavioral (mating calls), and genetic (DNA sequences) characters to study species boundaries between frogs of the genus Pristimantis and the family Centrolenidae (glassfrogs). The results show that the exclusive use of single lines of evidence or the application of arbitrary thresholds impair and bias our ability to recognize new species and limit the possibility to understand evolutionary processes. Only an integrative approach combining every source of evidence provides the necessary feedback to discover all species and test their identity by comparing independent sets of data. This approach further allows identifying those species that probably represent stable comparative units (well supported species hypotheses) and to flag taxa that require further assessment. Phylogenetic reconstructions based on seven nuclear and mitochondrial genes for about 100 species of glassfrogs revealed that previous hypotheses of relationships were mislead by rampant convergent evolution at the phenotypic level. None of the previously suggested classifications fit with the reconstructed evolutionary history. Consequently, we proposed a new classification consistent with this phylogeny. I also studied the tempo and mode of diversification among glassfrogs. Based on sequences from ten genes in 87 species, I estimated species divergence times, age-range correlation between sister species, and reconstructed ancestral areas and dispersal/vicariance events. The results revealed a complex model of diversification where geographical isolation seems to be the dominant scenario for speciation and only clades of altitudinal generalists have been able to spread across the Neotropical rainforests.

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