Disentangling the effects of historic vs. contemporary landscape structure on population genetic divergence

Authors

  • A. J. ZELLMER,

    1. Department of Ecology and Evolutionary Biology, University of Michigan, Museum of Zoology, 1109 Geddes Avenue, Ann Arbor, MI 48109-1079, USA
    Search for more papers by this author
  • L. L. KNOWLES

    1. Department of Ecology and Evolutionary Biology, University of Michigan, Museum of Zoology, 1109 Geddes Avenue, Ann Arbor, MI 48109-1079, USA
    Search for more papers by this author

  • Amanda J. Zellmer is a graduate student whose research focuses on the effects of landscape structure, demography, and selection on fine-scale population genetic structure as well as the role of genetic factors in population declines. Dr L. Lacey Knowles is an Associate Professor whose research focuses on the demographic and selective processes driving species divergence. Her research also addresses the methodological and statistical issues involved in studying species diversification, phylogeography, and phylogenetic relationships of recently diverged and rapidly speciating taxa.

Amanda J. Zellmer, Fax: 734-763-4080; E-mail: azellmer@umich.edu

Abstract

Increasing habitat fragmentation poses an immediate threat to population viability, as gene flow patterns are changed in these altered landscapes. Patterns of genetic divergence can potentially reveal the impact of these shifts in landscape connectivity. However, divergence patterns not only carry the signature of altered contemporary landscapes, but also historical ones. When considered separately, both recent and historical landscape structure appear to significantly affect connectivity among 51 wood frog (Rana sylvatica) populations. However, by controlling for correlations among landscape structure from multiple time periods, we show that patterns of genetic divergence reflect recent landscape structure as opposed to landscape structure prior to European settlement of the region (before 1850s). At the same time, within-population genetic diversities remain high and a genetic signature of population bottlenecks is lacking. Together, these results suggest that metapopulation processes – not drift-induced divergence associated with strong demographic bottlenecks following habitat loss – underlie the strikingly rapid consequences of temporally shifting landscape structure on these amphibians. We discuss the implications of these results in the context of understanding the role of population demography in the adaptive variation observed in wood frog populations.

Ancillary