RESUMO
Glacial-interglacial cycles of the Pleistocene are hypothesized as one of the foremost contributors to biological diversification. This is especially true for cold-adapted montane species, where range shifts have had a pronounced effect on population-level divergence. Gartersnakes of the Thamnophis rufipunctatus species complex are restricted to cold headwater streams in the highlands of the Sierra Madre Occidental and southwestern USA. We used coalescent and multilocus phylogenetic approaches to test whether genetic diversification of this montane-restricted species complex is consistent with two prevailing models of range fluctuation for species affected by Pleistocene climate changes. Our concatenated nuDNA and multilocus species analyses recovered evidence for the persistence of multiple lineages that are restricted geographically, despite a mtDNA signature consistent with either more recent connectivity (and introgression) or recent expansion (and incomplete lineage sorting). Divergence times estimated using a relaxed molecular clock and fossil calibrations fall within the Late Pleistocene, and zero gene flow scenarios among current geographically isolated lineages could not be rejected. These results suggest that increased climate shifts in the Late Pleistocene have driven diversification and current range retraction patterns and that the differences between markers reflect the stochasticity of gene lineages (i.e. ancestral polymorphism) rather than gene flow and introgression. These results have important implications for the conservation of T. rufipunctatus (sensu novo), which is restricted to two drainage systems in the southwestern US and has undergone a recent and dramatic decline.
Assuntos
Mudança Climática/história , Colubridae/genética , Demografia , Ecossistema , Variação Genética , Filogenia , Animais , Sequência de Bases , Primers do DNA/genética , DNA Mitocondrial/genética , Evolução Molecular , Fluxo Gênico/genética , Genética Populacional , Geografia , História Antiga , México , Modelos Genéticos , Modelos Teóricos , Dados de Sequência Molecular , Análise de Sequência de DNA , Sudoeste dos Estados UnidosRESUMO
Morphological identification of many fairy shrimp species is difficult because distinguishing characters are restricted to adults. We developed two multiplex polymerase chain reaction assays that differentiate among three Branchinecta fairy shrimp with distributional overlap in southern California vernal pools. Two of the species are federally listed as threatened. Molecular identification of Branchinecta from cysts allows for species surveys to be conducted during the dry season, expanding the timeframe for population assessment and providing a less intrusive method of sampling sensitive vernal pool habitats.
