Dissertation
On the role of historical constraint in evolution: An emphasis in salamander evolution
Washington State University
Doctor of Philosophy (PhD), Washington State University
05/2010
DOI:
https://doi.org/10.7273/000006048
Abstract
A fundamental challenge in evolutionary biology concerns estimating the extent to which ecological trade-offs impose constraints on evolution. In the first chapter, we test whether adaptive evolution of antipredator performance phenotypes in streamside salamanders was well predicted by stability in the selective regime experienced by salamander lineages. We found that the efficacy of antipredator phenotypes in salamanders is strongly related to historical duration, as well as consistency, of selection imposed by predatory fish on salamander larvae. Optimal circumstances for the evolution of effective antipredator responses in streamside salamanders seems to involve a long and consistent history of ecological contact with predatory fish. Evolutionary biologists have long debated the relative influence of species selection on evolutionary patterns. As a test in the second chapter, we assess whether variation in species ranges and in life-history contribute to patterns of diversification in salamanders. We find that paedotypy wherein some organisms of a species mature in the gilled form without metamorphosing is also associated with higher net diversification rates. Often dismissed as an insignificant process in evolution, this chapter, as well as the next, provides direct evidence for the role of species selection in lineage diversification of salamanders. The third chapter explores whether interspecific hybridism promotes or limits lineage diversification in salamanders. Using character-mediated diversification analyses and treating hybridism as a binary evolutionary character, results suggest that hybridism acts to swallow diversity. While evidence is provided for species selection generally disfavoring hybridism in a clade of amphibians, this chapter concludes with a discussion of circumstances where hybridism may be macroevolutionarily advantageous. The fourth chapter assesses whether coarse ecological differences among host populations are predictive of variation in forms of molecular selection in an emerging viral pathogen. We find elevated strengths of positive selection in pathogen strains associated with bait colonies of salamanders or in other captive-host environments. Given evidence of increased virulence associated with bait-associated strains of ATV, we argue that increased frequencies of tiger salamander epizootics in the western US are at least in part attributable to a relaxed virulence-transmission tradeoff in ATV-bait assemblages.
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Details
- Title
- On the role of historical constraint in evolution
- Creators
- Jonathan Michael Eastman
- Contributors
- Andrew T. Storfer (Chair)Mark Dybdahl (Committee Member) - Washington State University, School of Biological SciencesEric Roalson (Committee Member) - Washington State University, School of Biological SciencesLuke J Harmon (Committee Member)Matthew J Parris (Committee Member)
- Awarding Institution
- Washington State University
- Academic Unit
- School of Biological Sciences
- Theses and Dissertations
- Doctor of Philosophy (PhD), Washington State University
- Publisher
- Washington State University
- Number of pages
- 187
- Identifiers
- 99901055021201842
- Language
- English
- Resource Type
- Dissertation