Data from: Stretched to the limit; can a short pelagic larval duration connect adult populations of an Indo-Pacific diadromous fish (Kuhlia rupestris)?

Freshwater species on tropical islands face localized extinction and the loss of genetic diversity. Their habitats can be ephemeral due to variability in freshwater run-off and erosion. Even worse, anthropogenic effects on these ecosystems are intense. Most of these species are amphidromous or catadromous (i.e. their life cycle includes a marine larval phase), which buffers them against many of these effects. A long pelagic larval duration (PLD) was thought to be critical to ensure the colonization and persistence in tropical islands, but recent findings indicated that several species with short PLDs are successful in those ecosystems. To test the potential of a short PLD in maintaining genetic connectivity and forestalling extirpation, we studied Kuhlia rupestris, a catadromous fish species with an extensive distribution in the western Pacific and Indian Oceans. Using a combination of molecular genetic markers (13 microsatellite loci and two gene regions from mtDNA) and modelling of larval dispersal, we show that a short PLD constrains genetic connectivity over a wide geographical range. Molecular markers showed that the short PLD did not prevent genetic divergence through evolutionary time and speciation has occurred or is occurring. Modelling of larvae dispersal suggested limited recent connectivity between genetically homogeneous populations across the Coral Sea. However, a short PLD can maintain connectivity on a subocean basin scale. Conservation and management of tropical diadromous species needs to take into account that population connectivity may be more limited than previously suspected in those species.热带岛屿的淡水物种正面临局地灭绝与遗传多样性丧失的风险。受淡水径流量波动与侵蚀作用影响，其栖息地往往具有临时性。更为严峻的是，人类活动对这类生态系统的影响强度极高。 该类群中多数物种为双向洄游（amphidromous）或降海洄游（catadromous）类群，即其生命周期包含海洋幼体阶段，这一特性可帮助它们抵御诸多上述威胁。此前学界普遍认为，较长的海洋浮游幼体期（pelagic larval duration, PLD）是保障物种在热带岛屿成功定居并持续存续的关键，但最新研究表明，部分拥有较短PLD的物种同样能在这些生态系统中成功繁衍。 为验证短PLD在维持种群遗传连通性、延缓种群消亡方面的潜力，本研究以岩鲈（Kuhlia rupestris）为对象：该物种为降海洄游性鱼类，广泛分布于西太平洋与印度洋海域。本研究结合分子遗传标记（13个微卫星位点与两段线粒体DNA（mtDNA）基因区域）与幼体扩散模拟实验，证实短PLD会限制大范围地理尺度下的遗传连通性。 分子标记结果显示，短PLD并未阻碍演化进程中的遗传分化，物种形成事件业已发生或正在进行中。幼体扩散模拟结果表明，珊瑚海范围内遗传同质化种群间的近期连通性十分有限。不过，短PLD仍可在次洋盆尺度上维持种群连通性。 热带洄游性鱼类的保护与管理工作，需考虑到这类物种的种群连通性可能比此前预想的更为有限。