Genetic Diversity and Population Differentiation of Kashgarian Loach (Triplophysa yarkandensis) in Xinjiang Tarim River Basin

SIMPLE SUMMARY: The distribution of Kashgarian loach (Triplophysa yarkandensis) is limited to the Tarim River basin, which is the largest inland river in China. However, the population size of T. yarkandensis has been diminishing, and it is critically endangered in the Tarim River basin due to the gradual depletion of water resources, together with alien invasion and agricultural cultivation in Tarim River. In this study, we adopted the RAD-seq method to investigate the population genetics of T. yarkandensis, and a high degree of genetic variations and significant genetic differentiation was detected among T. yarkandensis populations in the Tarim River basin. The obtained data contribute to understanding the genetic status of T. yarkandensis, and help to provide the scientific management strategies and direct future monitoring and utilization of the genetic resource in Xinjiang region. ABSTRACT: The distribution of Triplophysa yarkandensis is restricted to Xinjiang’s Tarim River basin. We collected 119 T. yarkandensis samples from nine geographic populations in the Tarim River basin and utilized the RAD-seq method for SNP genotyping. In this study, a total of 164.81 Gb bases were generated with the Illumina platform, and 129,873 candidate SNPs were obtained with the Stacks pipeline for population genetic analyses. High levels of genetic diversity were detected among nine populations. The AMOVA results showed that the majority of genetic variations originated from among populations (F(ST) = 0.67), and the pairwise F(ST) values ranged from 0.4579 to 0.8736, indicating high levels of genetic differentiation among these populations. The discriminate analysis of principal components (DAPCs) and neighbor joining (NJ) tree revealed that the nine populations could be separated into two clusters (i.e., south and north populations), and modest genetic differentiation between south and north populations was observed, while the individuals from several populations were not clustered together by geographical location. The evidence of two genetic boundaries between south and north populations (except TTM) was supported by barrier analysis. The Bayesian skyline plotting indicated that T. yarkandensis populations in the Tarim River basin had not experienced genetic bottlenecks, and the effective population size remained stable. This study first clarified the genetic diversity and differentiation of T. yarkandensis populations in the Tarim River basin, and it provided valuable molecular data for conservation and management of natural populations.