Abstract
The Qinling Mountains of China provide an excellent study area for assessing the effect of Pleistocene climatic oscillations and paleogeological events on intraspecific diversification. To assess genetic diversity of an endemic stream salamander, Batrachuperus tibetanus, for its conservation, a phylogeographical survey was performed based on mitochondrial DNA and morphological data. The mitochondrial data revealed three lineages of B. tibetanus in the Qinling Mountains. A lineage present in the northwestern Qinling Mountains groups with the Tibet lineage of B. tibetanus, and the remaining Qinling populations are eastern and western lineages that separated ~3–4 million years ago (Ma). The eastern and western Qinling lineage delineation is supported by three morphological variables (snout length, eye diameter and axilla-groin length). The divergence of the two major lineages was likely caused by orogenesis of the Qinling Mountains during the late Cenozoic, and the two lineages were subsequently affected at different levels by Pleistocene climatic oscillations showing different signals of demographic expansion. A large suitable area of B. tibetanus through the Qinling Mountains since the last glacial maximum (LGM) indicated the adaptation of this species to the climatic changes. However, low genetic diversity within populations indicate the urgency of preserving the vulnerable populations and endemic lineages.
Highlights
Modern patterns of intraspecific genetic diversity presumably reflect cyclical Pleistocene climatic oscillations and Meso-Cenozoic intracontinental orogenesis
The length of the mitochondrial cytochrome b (Cyt b) gene sequences used in our analysis was 814 bp located 14, 258–15, 071 of the Genbank sequence NC_00808536, with 111 (13.6%) nucleotide sites being polymorphic in the total data, of which 105 were parsimony-informative
Our study revealed three lineages of B. tibetanus in the Qinling Mountains
Summary
Modern patterns of intraspecific genetic diversity presumably reflect cyclical Pleistocene climatic oscillations and Meso-Cenozoic intracontinental orogenesis. The stream salamanders living in the western high-elevation regions seem to have experienced colonization and population declines due to the last glaciation, while those in the eastern low-elevation regions appear to have experienced fragmentation during the extensive glacial period[26] It is unclear how the population-genetic diversity of B. tibetanus in the Qinling Mountains was structured by historical processes and affected by topography, glaciation and drainage. Drainage systems ascribed to the Yangtze River and Yellow River may have influenced the distribution and population structure of B. tibetanus in the Qinling Mountains, and generated a north-south break This hypothesis appears to be supported by the distinct climates and habitats at both slopes of the Qinling Mountains that serve as the boundary of the Palearctic and Oriental realms. The stream salamanders are generally distributed in the montane streams in the Qinling Mountains (>1200 m above sea level), and possibly affected by orogenesis of the Qinling Mountains and Pleistocene climatic oscillations[9,10,11,12,13] resulting in a west-east break
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