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Drainage basins serve as multiple glacial refugia for alpine habitats in the Sierra Nevada Mountains, California
  • Yi-Ming Weng,
  • David Kavanaugh,
  • Sean Schoville
Yi-Ming Weng
University of Wisconsin Madison Graduate School
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David Kavanaugh
California Academy of Sciences
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Sean Schoville
University of Wisconsin Madison
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Abstract

The evolutionary histories of alpine species are often directly associated with responses to glaciation. Deep divergence among populations and complex patterns of genetic variation have been inferred as consequences of persistence within glacier boundaries (i.e. on nunataks), while shallow divergence and limited genetic variation is assumed to result from expansion from large refugia at the edge of ice shields (i.e. massifs de refuge). However, for some species, dependence on specific microhabitats could profoundly influence their spatial and demographic response to glaciation, and such a simple dichotomy may obscure the localization of actual refugia. In this study, we use the Nebria ingens complex (Coleoptera: Carabidae), a water-affiliated ground beetle lineage, to test how drainage basins are linked to their observed population structure. By analyzing mitochondrial COI gene sequences and genome-wide single nucleotide polymorphisms, we find that the major drainage systems of the Sierra Nevada Mountains in California best explain the population structure of the N. ingens complex. In addition, we find that an intermediate morphotype within the N. ingens complex is the product of historical hybridization of N. riversi and N. ingens in the San Joaquin basin during glaciation. This study highlights the importance of considering ecological preferences in how species respond to climate fluctuations and provides an explanation for discordances that are often observed in comparative phylogeographic studies.

Peer review status:UNDER REVIEW

30 Aug 2020Submitted to Molecular Ecology
31 Aug 2020Assigned to Editor
31 Aug 2020Submission Checks Completed
11 Sep 2020Reviewer(s) Assigned