Contrasting population differentiation in two sympatric Triplophysa loaches on the Qinghai–Tibet Plateau

Abstract

Genetic differentiation in aquatic organisms is usually shaped by drainage connectivity. Sympatric aquatic species are thus expected to show similar population differentiation patterns and similar genetic responses to their habitats. Water bodies on the Qinghai–Tibet Plateau (QTP) have recently experienced dramatic physicochemical changes, threatening the biodiversity of aquatic organisms on the “roof of the world.” To uncover ecological genetics in Tibetan loaches (Triplophysa)—the largest component of the QTP ichthyofauna—we characterized population differentiation patterns and adaptive mechanisms to salinity change in two sympatric and phylogenetically closely related Tibetan loaches, T. stewarti and T. stenura, by integrating population genomic, transcriptomic, and electron probe microanalysis approaches. Based on millions of genome-wide SNPs, the two Tibetan loach species show contrasting population differentiation patterns, with highly geographically structured and clear genetic differentiation among T. stewarti populations, whereas there is no such observation in T. stenura, which is also supported by otolith microchemistry mapping. While limited genetic signals of parallel adaption to salinity changes between the two species are found from either genetic or gene expression variation perspective, a catalog of genes involved in ion transport, energy metabolism, structural reorganization, immune response, detoxification, and signal transduction is identified to be related to adaptation to salinity change in Triplophysa loaches. Together, our findings broaden our understanding of the population characteristics and adaptive mechanisms in sympatric Tibetan loach species and would contribute to biodiversity conservation and management of aquatic organisms on the QTP.

Mitochondrial genome data provide insights into the phylogenetic relationships within Triplophysa dalaica (Kessler, 1876) (Cypriniformes, Nemacheilidae)

“…Due to their widespread distribution, species of Triplophysa exhibit adaptability to diverse habitats, including cold environments, hypoxia, and saline waters. In recent years, multiple aspects including the phylogenetic relationships among Triplophysa species ( Wang et al 2016 , 2023 ; Chen et al 2019 ; Wu et al 2020 ), phylogeography ( Hu et al 2020 , 2022 ; Zhong et al 2022 ; Du et al 2023 ), patterns of population differentiation ( Zhou et al 2021b ; Jin et al 2022 ), and the adaptations to various habitats ( Chen et al 2020b , 2020a ; Zhang et al 2023 ) have been studied.…”

Factors limiting the spread of middle- and low-altitude fishes to the Qinghai-Tibet plateau

“…If it is selected as a control to study the adaptability of plateau fish to low temperature or low oxygen, it may cause the failure of experimental design. In addition, previous studies on the tolerance of plateau fish often focused on a single stress factor, and mostly used genetic analysis methods (Xu et al, 2016;Yang et al, 2020;Jin et al, 2022), lacking of stress tolerance experiments to verify. Therefore, the comparison of multi-group and multi-factor stress experiments can help us better understand the adaptation process of plateau fish and the causes of distribution pattern, so as to answer "why middle-and low-altitude fish cannot reach the plateau".…”