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 20 for “"Ecological speciation"”.
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Genetic architecture and ecological speciation in Heliconius butterflies
… now widely accepted that adaptation to different ecological niches can result in the evolution of new species. However, when gene flow persists speciation must overcome the antagonism between selection and recombination: Specifically, if gene flow persists, recombination will break down the …
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Assessing the drivers of adaptive radiation in a complex of gall midges: A multitrophic perspective on ecological speciation
Natural enemies as selective forces maintaining and shaping morphological, physiological, and behavioral divergence in adaptive radiations have received very little attention. Until recently, the focus has been on primary resource competition as a major driver of trait divergence in adaptive …
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Diet, adaptation and the evolution of assortative mating in Ceratitis capitata
… understood to be a primary driver of speciation and thus biodiversity. ‘Ecological speciation’ is now supported by evidence from numerous studies in a range of natural populations. However, experimental tests of the role of divergent natural selection in the establishment of …
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The effects of habitat on phenotype, growth and fitness in New Zealand triplefin fishes (Family: Tripterygiidae)
… taken place over evolutionary timescales (i.e. ecological speciation), are evident over ecological timescales. Of particular interest is how variation in the environment can lead to fitness differences that have evolutionary consequences. This was achieved by testing several proximate indicators …
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Reassessment of species limits and diversification process in the Cape grass genus Ehrharta Thunb
… most biodiverse floras in the world. Although ecological speciation is thought to be a primary mechanism behind diversification in the GCFR, it has recently been hypothesised that non-ecological speciation may have an influential role in driving diversification in the montane “sky islands” of …
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Macroevolution and phylogenomics in the adaptive radiation of Heliconiini butterflies
The recognition of ecological speciation and hybridisation as key components of speciation has led to a major shift in evolutionary biology over the last decade. The mimetic Heliconius butterflies of the Neotropics have served as a prominent example of both, although the vast majority of studies …
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Dispersal, gene flow, niche divergence and local adaptation in the hyper-diverse ruschioid Aizoaceae: testing alternative modes of speciation in the Knersvlakte quartz field flora of the Succulent Karoo, South Africa
What are the roles of alternative modes of speciation in the generation of biological diversity? This question is fundamental to the debate surrounding the origins of extraordinarily diverse regions and clades. Diversification in the Cape flora of South Africa has been intensively studied owing to …
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Linking ecological divergence and reproductive isolation: a tale of two killifish
… directly oppose genetic differentiation and speciation because they homogenize allele combinations that are unique to each population/species (Felsenstein 1981; Rieseberg 2001; Ortiz-Barrientos, Reiland et al. 2002; Butlin 2005). Under divergence with gene flow, either very strong selection …
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Morphometrics, molecular ecology and multivariate environmental niche define the evolutionary history of the Western Rattlesnake (Crotalus viridis) complex
… more deterministic work against the fluidity of speciation itself. This conceptual gap can be bridged through a comprehensive assessment of the nine subspecies comprising the historically enigmatic Western Rattlesnake (Crotalus viridis) complex, one that employs three disparate datasets. First, …
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Host use, mutualism and parasitism in the Lycaeides butterfly complex
… herbivorous insects can lead to diversification, speciation, and changes in other ecological interactions. In the first chapter, larval performance was investigated in three species of Lycaeides butterflies and placed into the context of other already studied ecological traits that potentially …
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A Geographic Mosaic of Speciation in Eurosta solidaginis
Ecological speciation occurs when divergent selection in different habitats creates strong selection for reproductive isolation which counteracts the homogenizing effects of gene flow between populations using those different habitats. Multiple divergent selection pressures can affect isolation and …
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Comparative Population Genomics and Speciation of Snakes Across the North American Deserts
<p>Understanding the process of speciation is of central interest to evolutionary biologists. Speciation can be studied using a phylogeographic approach, by identifying regions that promote lineage divergence, addressing whether speciation has occurred with gene flow, and when extended to multiple …
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Swimming in four goldfish (Carassius auratus) morphotypes: understanding functional design and performance through artificial selection
… envelope” of natural systems subject to ecological speciation.
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Adaptive radiation and speciation in African weakly-electric fish
… pre-zygotic isolation mechanisms, hence favoring ecological speciation in this group of fishes. Despite the evolutionary importance of this organ, genetic investigations regarding its origin and function have remained limited. The ultimate aim of this study is to better understand the genetic …
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The origin of alternative phenotypes in fishes
… should therefore be particularly worthwhile in speciation research. When alternative phenotypes are not entirely genetic they may arise as a result of developmental plasticity, when organisms develop in accordance with local abiotic and biotic conditions. Subject to developmental plasticity, …
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The Maintenance of Genetic Variation by Environmental Selection
… allows genetic differentiation, and therefore speciation, the process in which full reproductive isolation is achieved between populations, plays important role in generating biodiversity. In the second part of my dissertation I used Boechera stricta to address how environmental selection …
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Species delimitation and speciation process in the Seriphium plumosum L. complex (Gnaphalieae: Asteraceae) in South Africa
… and second, what are the key drivers of speciation? Steady efforts in taxonomy dating back to the early 17th century have led some to estimate that over 99% of species in the Cape flora have already been described. However, taxonomic research in the Cape has, as elsewhere, relied on …
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Chromosome and Genome Evolution in Culicinae Mosquitoes
… origin that have undergone incipient ecological speciation. The second goal was to study differences at the chromosome level between these two organisms. We first measured whole chromosome and chromosome arm length differences between Cx. p. molestus and Cx. p. pipiens as a basic …