Behavioral isolation is an important barrier to gene flow, contributing to the
formation and maintenance of animal species. Nevertheless, hybridization occurs more
commonly than is generally recognized, occurring in over ten percent of animal species
in the wild. Although the genetic consequences of hybridization are of considerable
interest given their evolutionary implications, the reasons that animals choose to mate
with other species are less clear. I apply mate choice theory to the question of
hybridization, using wood warblers (family Parulidae) and swordtail fishes (genus
Xiphophorus) as study systems.
Over half of the 45 species of North American wood warbler have produced
hybrids. Using comparative methods, I address the questions: Do ecological and
demographic factors predict hybridization in this family? Similarly, how do phylogeny,
song similarity, and sympatry with congeners correlate with hybridization? As with North
American wood warblers, behavioral isolation is also considered of primary importance
in isolating sympatric species of swordtail fishes. Two species, X. birchmanni and X.
malinche, hybridize in several locations in the wild. Through experimentation with these
and other Xiphophorus species, I investigate some of the factors that cause female mate
choice to vary, possibly contributing to hybridization. Specifically, I address the
following questions: Do females become less choosy when predation risk is high, or
encounter rates with conspecifics are low? Are female preferences for conspecifics
innate, or can they be modified by experience? And, do female preferences for
conspecifics vary among species, populations, or experiments?
These studies illustrate the utility of treating hybridization as just another possible
outcome of variation in mate choice. I find that warbler hybridization correlates with
ecological and other variables, that female swordtails become more responsive to
heterospecifics when mate choice is costly, and that female preferences for conspecifics
are species- and context-dependent. As animal hybridization can have important
evolutionary consequences, studying the factors that contribute to this variation can
enhance our understanding of the evolutionary process. / text
| Identifer | oai:union.ndltd.org:UTEXAS/oai:repositories.lib.utexas.edu:2152/ETD-UT-2011-05-3253 |
| Date | 04 June 2012 |
| Creators | Willis, Pamela Margaret |
| Source Sets | University of Texas |
| Language | English |
| Detected Language | English |
| Type | thesis |
| Format | application/pdf |
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