Evolution and phylogeography analysis of diploid and polyploid Misgurnus anguillicaudatus populations across China.

The origin and evolution of polyploid organisms have been extensively studied in plants, but this topic remains only partially understood in vertebrates, where polyploidy is relatively rare. In this study, we used Misgurnus anguillicaudatus, a fish that comprises five ploidy levels in nature, as a model animal to improve our understanding of biogeographic history and evolution of polyploid vertebrates. After collecting samples from different geographical populations in China, their ploidy levels were determined using flow cytometry. Two mitochondrial markers ( cytochrome b and control region) were then used for phylogeographic analyses to unravel the possible origins of diploids and tetraploids in China. The results showed that diploids have wider geographical distribution than tetraploids and triploids. There was no clear allopatric geographical range or boundary to divide diploid and polyploid populations. Rather, the analysis of mitochondrial DNA sequences indicated that tetraploids were autopolyploids, with lower genetic diversity than diploids. This suggests that tetraploids originated from sympatric diploids via multiple independent polyploidization events. Genetic structure patterns were similar between diploids and tetraploids, whereas complex genetic differentiation was found among different regions. The potential origin of M. anguillicaudatus was deduced to be in the Pearl River basin, which exhibited the highest nucleotide diversity and genetic differentiation. These findings provide insights into the evolution of polyploidy in vertebrates.