Speciation, phylogeography, and gene flow in giant salamanders (Dicamptodon)

Steele, Craig

From the Abstract: "Giant salamanders of the genus Dicamptodon occur in the Pacific Northwest of North America. The variety of geographic distributions and life history traits displayed among this genus provide opportunities to test hypotheses concerning regional biogeography, effects of Pleistocene glaciation, comparative phylogeography, and patterns of gene flow. A genus-level phylogeny was contructed to test competing biogeographic hypotheses concerning the disjunct distribution of the Idaho giant salamander (D. atterimus), and a Pleistocene speciation hypothesis for the Cope's giant salamander (D. copei). Results indicate speciation and distribution of D. aterrimus is attibutable to the orogeny of the Cascade Mountains rather than recent inland dispersal and that D. copei is distantly related to other coastal species and likely originated much earlier that the Pleistocene. Patterns of intraspecific variation were examined for the widespread Pacific giant salamander (D. tenebrosus) and hypotheses concerning the location and number of Pleistocene refugia were tested. Results indicate that D. tenebrosus was restricted to two Pleistocene refugia, one in the Columbia River valley and another in the Klamath-Siskiyou Mountains, and has recently expanded northward from these refugia into its current distribution. Phylogeogrphic patterns for D. copei were compared to that of the codistributed Van Dyke's salamander (Plethodon vandykei). Results reveal that sympatric populations displayed identical phylogeographic topologies, suggesting shared evolutionary histories, but topologies were ultimately incongruent due to several highly divergent allopatric populations of D. copei."

Speciation, phylogeography, and gene flow in giant salamanders (Dicamptodon)

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