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Phylogeography of the dusky shrew, Sorex monticolus (Insectivora, Soricidae): insight into deep and shallow history in northwestern North America

Authors

  • John R. Demboski,

    Corresponding author
    1. University of Alaska Museum and Biochemistry and Molecular Biology Program, University of Alaska Fairbanks, 907 Yukon Drive, Fairbanks, Alaska 99775–6960, USA
      J. R. Demboski. *Present address: Department of Biological Sciences, PO Box 443051, University of Idaho, Moscow, Idaho 83844–3051, USA. Fax: (208) 885–7905; E-mail:demboski@uidaho.edu
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  • Joseph A. Cook

    1. University of Alaska Museum and Biochemistry and Molecular Biology Program, University of Alaska Fairbanks, 907 Yukon Drive, Fairbanks, Alaska 99775–6960, USA
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    • Present address: Biological Sciences, Idaho State University, Pocatello, Idaho 83209–8007, USA.


J. R. Demboski. *Present address: Department of Biological Sciences, PO Box 443051, University of Idaho, Moscow, Idaho 83844–3051, USA. Fax: (208) 885–7905; E-mail:demboski@uidaho.edu

Abstract

Phylogenetic relationships among the dusky shrew (Sorexmonticolus) and eight related species (S. bairdi, S. bendirii, S. neomexicanus, S.ornatus, S. pacificus, S. palustris, S. sonomae and S.vagrans) were assessed using sequences from the mitochondrial cytochrome b gene (801 bp). Analyses using parsimony and maximum likelihood revealed significant molecular variation not reflected in previous morphological studies of these species. Conversely, three morphologically defined species (S.bairdi, S.neomexicanusandS.pacificus) were poorly differentiated. SorexornatusandS.vagrans represented basal taxa for a more inclusive group that included: (i) a widespread Continental clade containing S.monticolus (Arizona to Alaska, including S. neomexicanus); (ii) a Coastal clade containing S.monticolus (Oregon to south-east Alaska, including S. bairdiandS. pacificus); (iii) the semiaquatic species (S. bendiriiandS. palustris); and (iv) S.sonomae. Additional subdivision was observed within the Continental clade corresponding to populations from the northern and southern Rocky Mountains. Average uncorrected sequence divergence between the Coastal and Continental clades was 5.3% (range 4.5–6.2%), which exceeds many interspecific comparisons within this species complex and within the genus Sorex. Lack of resolution of internal nodes within topologies suggests a deep history of rapid diversification within this group. Late Pleistocene/Holocene glacial perturbations are reflected in the shallow phylogeographic structure within these clades in western North America. Our results suggest also that S. monticolus is not monophyletic under current taxonomic nomenclature. This perspective on phylogeographic history was developed within a growing comparative framework for other organisms in western North America.

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