Phylogeography and pleistocene evolution in the North American black bear |
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Authors: | Wooding S; Ward R |
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Institution: | Department of Biology, University of Utah, USA. stephen@nuer.iba.ox.ac.uk |
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Abstract: | To determine the extent of phylogeographic structuring in North American
black bear (Ursus americanus) populations, we examined mitochondrial DNA
sequences (n = 118) and restriction fragment length polymorphism profiles
(n = 258) in individuals from 16 localities. Among the bears examined, 19
lineages falling into two highly divergent clades were identified. The
clades differ at 5.0% of nucleotide positions, a distance consistent with
an origin 1.8 MYA, and have different but overlapping geographical
distributions. Areas of clade cooccurrence show that eastern and western
populations are currently mixing, but regional differences in lineage
distribution suggest that mixing has begun only recently. The long-term
population history of black bears appears to be characterized predominantly
by long-term regional isolation followed by recent contact and
hybridization. Congruence between the pattern of diversity observed in
black bears and patterns of forest refuge formation during the Pleistocene
supports earlier speculation that Pleistocene forest fragmentations
underlie a common pattern in the phylogeography of North American forest
taxa.
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