Population genetic structure is widespread in many organisms and can be found at
small spatial scales. Fine-scale differentiation is the result of ecological and
evolutionary processes working together to produce an overall pattern, but the relative
importance of these factors in population differentiation is poorly understood. The
goals of my research were to describe patterns of population genetic differentiation
and to identify ecological and evolutionary factors important for population
divergence. To this end, I investigated several aspects of genetic differentiation for
three vertebrates in northern California. The focal species were the terrestrial garter
snake (Thamnophis elegans) and the common garter snake (Thamnophis sirtalis) that
occupy a series of ponds, lakes and flooded meadows in northern California. I found
significant genetic differentiation and isolation by distance, as well as correlated
patterns of pairwise divergence in both species. Independent estimates of effective
population size and bi-directional migration rates also uncovered source-sink
dynamics in both species that suggest frequent extinction-recolonization events within
a metapopulation context. The generality of source-sink dynamics for an ecologically
similar species within the same ecosystem was explored using a third species, B.
boreas. I also identified ecological correlates of several population genetic parameters
for all three species. Although F[subscript ST] were similar, B. boreas had larger effective
population sizes, lower migration rates, lacked source-sink dynamics, and appeared to
be in migration-drift equilibrium, indicative of a temporally stable population
structure. A clustering analysis identified a series of block faults as a common barrier
to dispersal for both garter snakes, and ecological correlates were found to be more
similar among response variables than within species. I then compared degree of
genetic differentiation at quantitative traits with that at neutral markers to infer
strength of selection and adaptive divergence between two ecotypes of T. elegans.
Selection on most traits was relatively weak, but strong diversifying selection was
found for background coloration, total number of ventral scales and number of
infralabials. Overall, my research documented ecological and evolutionary processes
associated with population differentiation in a metacommunity and respresents an
important contribution toward the unification of ecology and evolutionary biology. / Graduation date: 2005
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/28993 |
| Date | 28 January 2005 |
| Creators | Manier, Mollie Kim |
| Contributors | Arnold, Stevan J. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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