DataSheet1_The role of landscape evolution in the genetic diversification of a stream fish Sarcocheilichthys parvus from Southern China.pdf

Sarcocheilichthys parvus (Cypriniformes: Gobionidae) is a stream fish which is endemic to sub-tropical coastal drainages in southern China, thus offering a valuable model for understanding how genetic divergence arises in stream-adapting freshwater fishes in this region. Using the mitochondrial Cyt b gene, integrative analyses of phylogeny, population demography, and ancestral area and paleo-drainage reconstructions are carried out to explicitly explore the role of landscape evolution in genetic diversification of S. parvus. The time-calibrated phylogeny of S. parvus indicates the splitting of two major lineages (A and B) at ∼3.66 Ma. Lineage A inhabits the Poyang Lake sub-drainage of the middle Yangtze River, Han River and Pearl River, and can be split into two sub-lineages (A-I and A-II), where sub-lineage A-II can be further sub-divided into three infra-sub-lineages (A-IIa, A-IIb and A-IIc). Except for the infra-sub-lineage A-IIc, which is restricted to the Han River and Pearl River, the other sub-lineages and infra-sub-lineages live exclusively in the Poyang Lake sub-drainage. Lineage B lives in the lower Yangtze River, Qiantang River, Jiaojiang River and Ou River, displaying close genetic relationships among the drainages. Rapid population expansion has occurred since the Late Pleistocene. Our findings indicate that the splitting of lineages A and B could be attributed to geographic isolation due to the Zhe–Min Uplift, acting as a biogeographic barrier before the late Early Pleistocene. Furthermore, the strong genetic divergence within Lineage A could be explained by the isolation role of the Nanling Mountains and Poyang Lake acting as an ecological barrier; while the lack of phylogenetic structure within Lineage B may have been the result of paleo-drainage connections or episodic freshwater connections during the eustatic low stand of sea level in the late Middle–Late Pleistocene.

小鳈（Sarcocheilichthys parvus，鲤形目：鮈科）是一种溪流鱼类，为中国南部亚热带沿海水系特有种，是探究该区域溪流适应性淡水鱼类遗传分化起源的优质模型。本研究基于线粒体细胞色素b（Cyt b）基因，通过整合系统发育、种群动态、祖先分布区及古水系重建分析，明确探讨了地貌演化在小鳈遗传分化中的作用。小鳈的时间校准系统发育树显示，两大支系（A与B）的分化时间约为3.66百万年前。支系A分布于长江中游鄱阳湖水系、汉江及珠江流域，可进一步分为两个亚支系（A-I与A-II）；其中A-II亚支系还可细分为3个下级亚支系（A-IIa、A-IIb与A-IIc）。仅下级亚支系A-IIc局限分布于汉江与珠江流域，其余亚支系及下级亚支系均仅见于鄱阳湖水系。支系B分布于长江下游、钱塘江、椒江及瓯江水系，各水系间遗传关系紧密。自晚更新世以来，该物种种群经历了快速扩张。本研究结果表明，支系A与B的分化可归因于浙闽隆起带在早更新世晚期前作为生物地理屏障所造成的地理隔离。此外，支系A内部显著的遗传分化可由南岭及鄱阳湖作为生态屏障所造成的隔离作用解释；而支系B内部缺乏系统发育结构，可能源于中更新世晚期至晚更新世期间全球海平面低位时期的古水系连通或间歇性淡水水体连通。