Genetic diversity of the regionally endangered Chinese ricefish (Oryzias sinensis) in Taiwan, with comments on its conservation status

The Chinese ricefish (Oryzias sinensis) is a freshwater fish that is regionally endangered in Taiwan. To evaluate its conservation status and further formulate conservation plans for this species in Taiwan, this study analyzed the fish collected from all known localities, including a newly discovered population. The phylogenetic trees based on D-loop and COI divided the Chinese ricefish into two major clades: Taiyangpi-Shuanglienpi and Taiping-Gongliao. This study showed that both the Shuanglienpi and Taiyangpi wild populations had significantly higher Hd and π values, while the Shuanglienpi restored population only had one haplotype from the wild. However, their genetic diversity may have decreased over the past few decades. The Gongliao and Taiping populations shared the same haplotype as a population from a previous study. We propose that the Gongliao and Taiping populations were founded by a few individuals and might have originated from a single introduction event from southeastern mainland China. Low genetic diversity was clearly observed in the Taiping, Gongliao and Shuanglienpi restored populations. Based on the present investigation and previous studies, the invasive poeciliid fish (such as mosquitofish and green swordtail) contribute the most to the decline of the Chinese ricefish population and genetic diversity in Taiwan.