Introgressive hybridization as a mechanism for species rescue |
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Authors: | Marissa L Baskett Richard Gomulkiewicz |
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Institution: | (1) Department of Environmental Science and Policy, University of California, Davis, One Shields Ave, Davis, CA 95616-5270, USA;(2) School of Biological Sciences, Washington State University, Pullman, WA 99164, USA |
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Abstract: | Rapid evolution on ecological time scales can play a key role in species responses to environmental change. One dynamic that
has the potential to generate the diversity necessary for evolution rapid enough to allow response to sudden environmental
shifts is introgressive hybridization. However, if distinct sub-species exist before an environmental shift, mechanisms that
impede hybridization, such as assortative mating and hybrid inferiority, are likely to be present. Here we explore the theoretical
potential for introgressive hybridization to play a role in response to environmental change. In particular, we incorporate
assortative mating, hybrid inferiority, and demographic stochasticity into a two-locus, two-allele population genetic model
of two interacting species where one locus identifies the species and the other determines how fitness depends on the changing
environment. Simulation results indicate that moderately high values for the strength of assortative mating will allow enough
hybridization events to outweigh demographic stochasticity but not so many that continued hybridization outweighs backcrossing
and introgression. Successful introgressive hybridization also requires intermediate relative fitness at the allele negatively
affected by environmental change such that hybrid survivorship outweighs demographic stochasticity but selection remains strong
enough to affect the genetic dynamics. The potential for successful introgression instead of extinction with greater environmental
change is larger with monogamous rather than promiscuous mating due to lower stochasticity in mating events. These results
suggest species characteristics (e.g., intermediate assortative mating and mating systems with low variation in mating likelihood)
which indicate a potential for rapid evolution in response to environmental change via introgressive hybridization. |
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