Phylogeographic analyses of Sarcocheilichthys nigripinnis(Teleostei：Cyprinidae)based on mitochondrial DNA Cyt b gene sequences

Sarcocheilichthys nigripinnis is a small cyprinid fish widely distributed in East Asia, and it has been widely used in biogeographic analyses of freshwater fishes in China. In the present study, 142 S. nigripinnis individuals from 20 sampling sites in eight river systems were collected to investigate its phylogeography and genetic variations.. Populations from the Yellow River represent northern clade and all others represent southern clade. The results showed that 56 haplotypes were identified as mitochondrial DNA (mtDNA) Cyt b gene of 1 140 bp length. Relatively high haplotype diversity (h=0.971) and low nucleotide diversity (π=0.0212) were detected, and the estimated average genetic distance was 2.2%. Moreover, a neighbor-joining(NJ)tree revealed seven strongly supported lineages. Populations from the Yellow River were located at the basal position, whereas the remaining populations were more derived. Our results indicate that S. czerskii might have been evolved from S. nigripinnis in the Yellow River ~1.03 Ma. Based on the phylogeographical analysis of S. nigripinnis, we also suggest that vicariance, following mountain uplift and drainage isolation, plays an important role in producing evolutionary lineage differentiations. Moreover, molecular dating estimated that the divergence time of S. czerskii could be dated back to 0.95~3.92 Ma. Mismatch distribution analysis and neutrality tests also suggested the recent demographic expansions of S. nigripinnis populations, and that the effects of Pleistocene climatic changes could be a vital factor of the population dynamics of S. nigripinnis.