Genetic diversity and population structure of the invasive populations of goldfish Carassius auratus complex in Tibet

The goldfish Carassius auratus complex is one of the most successfully invasive fish species on the Tibetan Plateau. However, little is known about the ploidy distribution of the invasive populations and their evolutionary dynamics. Here, using mitochondrial D-loop and eight microsatellites, we evaluated the genetic diversity and population structure of three invasive populations from Tibet and 12 native populations from six rivers including the Yangtze River and Yellow River which were assumed to be the sources by market survey. The proportions of diploids ranged from 0 to 61% in the three invasive populations. A total of 60 and 57 D-loop haplotypes were detected from 344 diploids and 838 triploids, respectively, with 28 haplotypes being shared. For diploids, the haplotype diversity (Hd: 0.600–0.655) and mean observed heterozygosity ( H O : 0.871–0.888) of microsatellites of invasive populations were lower than those of source populations (Hd: 0.883–0.950, H O : 0.891–0.982). However, for triploids, invasive populations also had lower Hd values (0.617–0.816) but comparable H O values (0.900–0.933) than the source populations (Hd: 0.838–0.918, H O : 0.925–0.948). The structure analysis for diploids showed that all invasive individuals shaped one single genetic cluster which was separated from native individuals. For triploids, no genetic separation was observed between invasive and native populations. Our results demonstrated the difference in ploidy ratio among invasive populations may be related to wetlands’ open state, and the diploids rather than triploids of goldfish experienced obvious changes of genetic diversity and population structure during their invasion to Tibet.