Theses (M.S.)--Marshall University, 2006. / Title from document title page. Includes abstract. Document formatted into pages: contains xiii, 82 p. including col. illustrations and maps. Bibliography: p. 66-76.

Thesis (Ph. D.)--University of Texas at Austin, 2007. / Vita. Includes bibliographical references.

No description available.

The most urgent amphibian conservation issue in the Upper Midwest has been Blanchard's cricket frog (Acris crepitans blanchardi) declines over much of their northern range. Several causes have been proposed to explain these declines, including pesticide applications, disease, habitat loss, and habitat modification. My goal was to explore these proposed causes. Using a combination of field and laboratory analyses, including population analyses, gross inspections for malformations, and a histopathological analysis for indicators of fungus, disease and parasites, I found evidence for disease (a viral infection) and stress (fluctuating asymmetry, malformations and parasitism). Interestingly, the population most affected by these factors was also the one that contained the most animals and was located south of the presumed decline front (i.e., was assumed to be healthy). / Department of Biology

During speciation, populations become spatially separated from each other by biotic or abiotic factors, and this leads to genetic divergence and reproductive isolation. Here, I study the process of speciation and the patterns resulting from this process in the chorus frogs (Pseudacris). I first lay the foundation for this work by constructing phylogenies based on molecular data. I then address broad-scale questions regarding the abiotic factors thought to drive speciation. I examine evolution of reproductive signals within a phylogenetic context, and finally, I address fine-scale questions regarding the completion of reproductive isolation in contact zones between recently-evolved species. In chapter 1, I estimate the phylogenetic relationships across the genus Pseudacris. I find that several species of unclear status (regilla, cadaverina, crucifer, ocularis) belong to this genus, and that P. ocularis is the sister species of P. crucifer. In chapter 2, I examine the phylogeography of a clade within Pseudacris, the trilling chorus frogs. I find support for at least nine species and delineate their geographic distributions. In chapter 3, I test geological and climatic hypotheses proposed to drive speciation in North American flora and fauna. By estimating divergence times in the trilling chorus frogs and correlating these divergences with timing of geologic events, I find that marine inundation of the Mississippi Embayment may have caused speciation in this group. Additionally, I find that climatic events led to reduced genetic variation rather than divergence within species. In chapter 4, I study the evolution of acoustic signals of all species of Pseudacris. Using a comparative method approach, I find that physiologybased call variables are more evolutionarily labile than morphology-based call variables. In addition, I find that sympatric signals are more different than allopatric signals, suggesting that these frogs have partitioned the acoustic niche. In chapter 5, I examine evolution of reproductive isolation between two chorus frog species in sympatry. I find that male signals show a repeated pattern of divergence in sympatry, and that different axes of the signal diverge in different populations, suggesting that heterospecific overlap may lead to reproductive isolation among conspecific populations. I also find that female preferences have evolved in sympatry, suggesting that divergence in the contact zone is due to reinforcement.

Thesis (Ph. D.)--University of Missouri-Columbia, 2008. / The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file (viewed on July 28, 2009) Includes bibliographical references.

Thesis (Ph. D.)--University of Alberta, 2010. / Title from pdf file main screen (viewed on June 11, 2010). A thesis submitted to the Faculty of Graduate Studies and Research in partial fulfillment of the requirements for the degree of Doctor of Philosophy in Environmental Biology and Ecology, Department of Biological Sciences, University of Alberta. Includes bibliographical references.

No description available.