Balancing selection and drift in a polymorphic salamander metapopulation |
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Authors: | Sean T Giery Marketa Zimova Dana L Drake Mark C Urban |
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Institution: | 1.Department of Biology, The Pennsylvania State University, University Park, PA 16802, USA;2.School for Environment and Sustainability, University of Michigan, Ann Arbor, MI 48109, USA;3.Department of Ecology and Evolutionary Biology; Center of Biological Risk, University of Connecticut, Storrs, CT 06269, USA |
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Abstract: | Understanding how genetic variation is maintained in a metapopulation is a longstanding problem in evolutionary biology. Historical resurveys of polymorphisms have offered efficient insights about evolutionary mechanisms, but are often conducted on single, large populations, neglecting the more comprehensive view afforded by considering all populations in a metapopulation. Here, we resurveyed a metapopulation of spotted salamanders (Ambystoma maculatum) to understand the evolutionary drivers of frequency variation in an egg mass colour polymorphism. We found that this metapopulation was demographically, phenotypically and environmentally stable over the last three decades. However, further analysis revealed evidence for two modes of evolution in this metapopulation—genetic drift and balancing selection. Although we cannot identify the balancing mechanism from these data, our findings present a clear view of contemporary evolution in colour morph frequency and demonstrate the importance of metapopulation-scale studies for capturing a broad range of evolutionary dynamics. |
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Keywords: | Ambystoma maculatum eco-evolutionary dynamics population size historical resurvey microgeographic variation contemporary evolution |
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