Genetic diversity and genetic differentiation of Megalobrama populations inferred by mitochondrial markers

Megalobrama is economically one of the most important freshwater fish genera in China. However, phylogenetic relationships among M. amblycephala, M. skolkovii, M. hoffmanni and M. pellegrini remain unresolved. To explore the genetic diversity and phylogenetic relationship of Megalobrama populations belonging to all four species. The concatenated sequences of mitochondrial cytochrome b (Cytb) and control region (CR) were used to analyze the genetic variation, genetic differentiation and population expansion of 15 Megalobrama populations. The study showed that haplotype diversity and nucleotide diversity of M. hoffmanni and M. skolkovii were high, and that M. hoffmanni was the most genetically divergent of the four species. Haplotype network analysis revealed that M. hoffmanni and M. amblycephala formed a monophyletic group each, while M. skolkovii and M. pellegrini clustered together. There was a high genetic differentiation among the four Megalobrama species, and genetic distance among populations was not affected by geographical distance. Additionally, the results indicated that there was gene flow between the Liangzi Lake (LZL) population and Jinsha River Reservoir (JS) population. Also, Zhaoqing (ZQ) population of M. hoffmanni might have experienced a population expansion. Our study verifies genetic diversity and differentiation of Megalobrama populations, and these findings will represent a significant contribution to the conservation and utilization of germplasm resources of Megalobrama.