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Cryptic Neogene Vicariance and Quaternary Dispersal of the Red-Spotted Toad (Bufo Punctatus) Insights on the Evolution of North American Warm Desert Biotas

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Abstract:We define the geographic distributions of embedded evolutionary mitochondrial DNA (mtDNA) lineages (clades) within a broadly distributed, arid- dwelling toad, Bufo punctatus, and evaluate these patterns as they relate to hypothesized vicariant events leading to the formation of biotas associated with the major warm desert regions of western North America. To complement deeper scale phylogenetic analyses, we nested parsimony-based haplotype networks within the major identified evolutionary lineages and applied nested clade analysis (NCA) to further elucidate and evaluate more recent phylogeographic patterns potentially associated with Quaternary (Pleistocene-Holocene) vicariance and dispersal. We assessed mtDNA variation among 187 samples from 80 sites located throughout most of the species range. Phylogenetic analyses provided strong support for three monophyletic clades within B. punctatus. Sequence divergences among these major clades were almost identical, and phylogenetic analyses revealed no support for any particular branching order among the clades. The observed divergence levels and congruence with postulated events in earth history implicate a Late Neogene (Late Miocene-Pliocene) time-frame for the separation of the major mtDNA lineages.
The geographic distributions of haplotypes within the three major clades showed little overlap and corresponded to the general boundaries of the Peninsular Desert, and two continental desert clades, Eastern (Chihuahuan Desert-Colorado Plateau) and Western (Mojave-Sonoran deserts), geographically separated along the Rocky Mountains and the Sierra Madre Occidental (roughly the continental divide). Evaluation of nucleotide and haplotype diversity and interpretations from NCA revealed that Eastern clade populations on the Colorado Plateau are a result of recent range expansion, most likely post-Pleistocene, from populations in the Chihuahuan Desert. The Western clade appears to have maintained some populations within the Mojave Desert during recent Pleistocene times. We identified two locations where the major continental clades are in current contact and speculate as to why the observed deep phylogeographic structure has not been eroded during the multiple previous interglacials during the Pleistocenerecent range expansion, most likely post-Pleistocene, from populations in the Chihuahuan Desert. The Western clade appears to have maintained some populations within the Mojave Desert during recent Pleistocene times. We identified two locations where the major continental clades are in current contact and speculate as to why the observed deep phylogeographic structure has not been eroded during the multiple previous interglacials during the Pleistocene.
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Citation:Jaeger, J. R., B. R. Riddle, and D. F. Bradford. Cryptic Neogene Vicariance and Quaternary Dispersal of the Red-Spotted Toad (Bufo Punctatus) Insights on the Evolution of North American Warm Desert Biotas. MOLECULAR ECOLOGY. Blackwell Publishing, Malden, MA, 14:3033-3048, (2005).
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Contact: Chris Siebert - (702) 798-2234 or siebert.christopher@epa.gov
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Division: Environmental Sciences Division
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Branch: Landscape Ecology Branch
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Product Type: Journal
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Published: 08/22/2005
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Bullet Item Cryptic Neogene Vicariance and Quaternary Dispersal of the Red-Spotted Toad (Bufo Punctatus) Insights on the Evolution of North American Warm Desert Biotas
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Related Entries:
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Bullet Item Development of Landscape Indicators for Use in Regional Ecological Risk Assessments
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