基于RAD-seq技术解析雅鲁藏布江异齿裂腹鱼的群体分化及其成因

Schizothorax o’connori is a rare and endemic fish in Tibet of China, it is a only Schizothorax species that is distributed in both the western and eastern drainages of the Yarlung Tsangpo Grand Canyon (YTGC) in the Yarlung Tsangpo River (YLTR). However, published research and our latest genetic analysis indicated that there were remarkable distinctions in morphorlogical characters and genetic relationship between the populations above the YTGC and below the YTGC of the YLTR. Because it is concerns with effective protection and management of Schizothorax o’connori resources in the YLTR basin, we should make further studies to validate the previous reported population differentiation and further probe into the causes of it. The high-throughput RAD-seq technique can be effectively used to accurately analyze population genetic structure and phylogeny of species. To study population differentiation of Schizothorax o’connori from both the western and eastern drainages of the YTGC, this project plans to investigate genetic structure and phylogeography of 10-12 populations firstly using the RAD-sequencing and mtDNA sequence analyses. In the meantime, landscape genetics will be used to test the effect of site-specific hydrological and enviromental factors of the YLTR on the population genetic variation of this species. Subsequently, by comparative analysis with the differences in morphological and reproductive characteristics among those potential differentiated populaions, we will infer the causes of the population differentiation of this fish species.The implementation of this project will help to provide reliable evidence for the protection and management of Schizothorax o’connori resources, and to deepen our understanding of the population differentiation and ecological adaptability of Schizothorax o’connori in extreme environments on the Qinghai-Tibet plateau.

异齿裂腹鱼是西藏特有珍稀鱼类，是唯一分布于雅鲁藏布江大峡谷东、西两侧流域的裂腹鱼属种类。前人的报道及我们前期遗传分析表明，雅江大峡谷东、西两侧流域异齿裂腹鱼群体在形态和遗传关系上差异明显，分属不同种群。事关异齿裂腹鱼种质资源有效保护和管理，亟待对其群体分化进行确证，并解析群体分化成因。高通量RAD-seq技术在准确分析群体遗传结构和系统演化方面成效显著。本项目拟在雅江大峡谷东、西两侧流域干流及支流采集10～12个异齿裂腹鱼群体，通过RAD-seq测序和线粒体DNA序列分析，对不同群体的遗传结构和谱系地理学进行深入研究，确证是否存在显著群体分化。采用景观遗传学分析雅江水文和环境因子对异齿裂腹鱼群体遗传变异的影响，结合对潜在分化群体间形态和繁殖生物学特征的比较分析，探究群体分化原因。本项目的实施，将为雅江异齿裂腹鱼种质资源保护提供可靠依据，并加深对高原极端环境下鱼类群体分化和生态适应性的认识。

异齿裂腹鱼是西藏特有珍稀鱼类，是唯一分布于雅鲁藏布江大峡谷东、西两侧流域的裂腹鱼属种类。前人的报道及我们前期遗传分析表明，雅江大峡谷东、西两侧流域异齿裂腹鱼群体在形态和遗传关系上差异明显，分属不同种群。事关异齿裂腹鱼种质资源有效保护和管理，亟待对其群体分化进行确证，并解析群体分化成因。本项目以大峡谷东西两侧流域10个异齿裂腹鱼群体为研究对象，基于RAD-seq测序和线粒体DNA序列对异齿裂腹鱼群体遗传结构和谱系地理学做了分析，对群体之间鱼体外部形态、耳石形状、耳石核心区元素的差异进行了多元统计分析等相关研究，结果表明：大峡谷东、西两侧异齿裂腹鱼群体间不仅存在显著遗传结构和遗传分化，而且存在外部形态、耳石形状、耳石核心区元素含量的显著分化。结果为解析雅江异齿裂腹鱼群体分化原因并促进其种质资源保护提供科学数据和理论依据。取得的主要结果如下：.1.基于RAD-seq的群体遗传学和谱系地理学分析，明确大峡谷东侧通麦群体与西侧8个群体显著分化为2个进化显著单元，西侧8个群体包含2个遗传谱系。.2.线粒体COI和ND4序列分析揭示大峡谷东侧通麦、卡达桥群体与西侧8个群体之间存在显著遗传分化。.3.形态度量学分析揭示大峡谷东、西两侧群体之间存在显著外部形态分化和明显耳石形态分化。.4.耳石核心元素比例性状的多元分析揭示大峡谷东侧通麦群体耳石核心Sr:Ca、Ba:Ca两个比例性状与西侧8个群体之间存在显著差异，提示大峡谷东、西两侧群体在胚胎和早期发育阶段生活于不同栖息环境而处于地理隔离状态。.5.推测雅鲁藏布大峡谷形成所导致的地理隔离可能是大峡谷东、西两侧异齿裂腹鱼在适应性进化中发生显著遗传分化和形态分化的成因。建议将大峡谷东侧群体、西侧群体划分为2个进化显著单元进行保护和管理，将大峡谷西侧8个群体划分为2个管理单元（拉孜/日喀则/墨竹工卡，桑日/加查/朗县/米林/派镇）进行保护和管理。