Geographical differentiation of the Euchiloglanis fish complex (Teleostei: Siluriformes) in the Hengduan Mountain Region, China: Phylogeographic evidence of altered drainage patterns.

The uplift of the Tibetan Plateau caused significant ecogeographical changes that had a major impact on the exchange and isolation of regional fauna and flora. Furthermore, Pleistocene glacial oscillations were linked to temporal large-scale landmass and drainage system reconfigurations near the Hengduan Mountain Region and might have facilitated speciation and promoted biodiversity in southwestern China. However, strong biotic evidence supporting this role is lacking. Here, we use the Euchiloglanis fish species complex as a model to demonstrate the compound effects of the Tibetan Plateau uplift and Pleistocene glacial oscillations on species formation in this region. The genetic structure and geographical differentiation of the Euchiloglanis complex in four river systems within the Hengduan Mountain Region were deduced using the cytochrome b (cyt b) gene and 10 microsatellite loci from 360 to 192 individuals, respectively. The results indicated that the populations were divided into four independently evolving lineages, in which the populations from the Qingyi River and Jinsha River formed two sub-lineages. Phylogenetic relationships were structured by geographical isolation, especially near drainage systems. Divergence time estimation analyses showed that the Euchiloglanis complex diverged from its sister clade Pareuchiloglanis sinensis at around 1.3 Million years ago (Ma). Within the Euchiloglanis complex, the divergence time between the Dadu-Yalong and Jinsha-Qingyi River populations occurred at 1.0 Ma. This divergence time was in concordance with recent geological events, including the Kun-Huang Movement (1.2-0.6 Ma) and the lag time (<2.0 Ma) of river incision in the Hengduan Mountain Region. Population expansion signals were detected from mismatched distribution analyses, and the expansion times were concurrent with Pleistocene glacier fluctuations. Therefore, current phylogeographic patterns of the Euchiloglanis fish complex in the Hengduan Mountain Region were influenced by the uplift event of the Tibetan Plateau and were subsequently altered by paleo-river transitions during the late Pleistocene glacial oscillations.