Abstract:

To assess the genetic diversity, population structure and demographic history of Neosalanx jordani, we sequenced complete mitochondrial DNA (1,141 bp) from the cytochrome b (cyt b) gene for 129 individuals from five populations in the Yangtze River and the Huaihe River basins. We identified18 haplotypes, and haplotype diversity was high (h=0.590±0.047). Nucleotide diversity was relatively low (π = 0.00088±0.00011) among all haplotypes. Phylogenetic analysis failed to detect significant geographic structure. Analysis of molecular variance (AMOVA) revealed significant genetic subdivision among individuals within populations and among populations within basins but not between basins, indicating distribution of genetic diversity was inconsistent with contemporary hydrological structure. We suggest that the present complex genetic pattern ofN. jordani resulted from multiple unrelated founding dispersal events (long-distance colonization), contiguous population expansion, and restricted gene flow. Demographic analysis revealed that this species may have experienced a relatively recent population expansion, and the majority of mutations occurred 18.97 kyr ago. This timing is consistent with the estimated time of sea level rise and the formation of large-scale appropriate habitats during the last glacial maximum (LGM). Thus, we suggest that all populations, especially those with high genetic diversity, should be separately managed and conserved.

Key words: Neosalanx jordani, cytochrome b, genetic structure, demographic history