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Pleistocene glaciation leaves deep signature on the freshwater crab Aegla alacalufi in Chilean Patagonia

Authors

  • JIAWU XU,

    1. Department of Biology & Monte L. Bean Life Science Museum, Brigham Young University, Provo, UT 84602, USA,
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  • MARCOS PÉREZ-LOSADA,

    1. Department of Biology & Monte L. Bean Life Science Museum, Brigham Young University, Provo, UT 84602, USA,
    2. CIBIO, Centro de Investigação em Biodiversidade e Recursos Genéticos, Universidade do Porto, Campus Agrário de Vairão, 4485-661 Vairão, Portugal,
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  • CARLOS G. JARA,

    1. Instituto de Zoología, Universidad Austral de Chile, Casilla 567, Valdivia, Chile
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  • KEITH A. CRANDALL

    1. Department of Biology & Monte L. Bean Life Science Museum, Brigham Young University, Provo, UT 84602, USA,
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Jiawu Xu, Fax: +1801 4220090; E-mail: jxu22@byu.edu

Abstract

Quaternary glacial cycles have played an important role in shaping the biodiversity in temperate regions. This is well documented in Northern Hemisphere, but much less understood for Southern Hemisphere. We used mitochondrial DNA and nuclear elongation factor 1α intron sequences to examine the Pleistocene glacial impacts on the phylogeographical pattern of the freshwater crab Aegla alacalufi in Chilean Patagonia. Phylogenetic analyses, which separated the glaciated populations on eastern continent into a north group (seven populations) and a south group (one population), revealed a shallow phylogenetic structure in the north group but a deep one in the non-glaciated populations on western islands, indicating the significant influence of glaciation on these populations. Phylogenies also identified the Yaldad population on Chiloé Island as a potentially unrecognized new species. The non-glaciated populations showed higher among population genetic divergence than the glaciated ones, but lower population genetic diversity was not detected in the latter. The two glaciated groups, which diverged from the non-glaciated populations at ~96 800–29 500 years ago and ~104 200–73 800 years ago, respectively, seem to have different glacial refugia. Unexpectedly, the non-glaciated islands did not serve as refugia for them. Demographic expansion was detected in the glaciated north group, with a constant population increase after the last glacial maximum. Nested clade analyses suggest a possible colonization from western islands to eastern continent. After arriving on the continent and surviving the last glacial period there, populations likely have expanded from high to low altitude, following the flood of melting ice. Aegla alacalufi genetic diversity has been primarily affected by Pleistocene glaciation and minimally by drainage isolation.

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