DISSERTATION RESEACH: Thermal Fragmentation and Genetic Differentiation of Fish Populations in a Riverine Landscape

流水的巨大用途导致了对世界各地溪流和河流的广泛开发，这一过程在全球范围内建造了数十万座水坝，大大促进了这一进程。众所周知，水坝通过阻止个体在完成其生命周期所需的基本栖息地之间的流动(例如太平洋西北部的鲑鱼物种)，对景观产生了碎片化的影响。此外，世界各地的许多大坝通过选择性地从水库中释放冷水，极大地改善了下游环境，以便在堤坝河流的尾水段建立生产性鲑鱼渔业。我们最近在美国东南部的研究表明，从温水生境转变为冷水生境可能会导致尾水中鱼类种群的显著损失，而毗邻的温水支流提供热避难所，并包含极其密集和多样化的鱼类群落。这些结果导致了一种假设，即冷水释放坝可能通过限制鱼类在寒冷的尾水中的运动而产生额外的碎裂效应，随着时间的推移，这可能导致支流鱼类种群的遗传分化。我们通过研究3种鱼的遗传结构来解决这一假设，这些鱼在一系列支流中表现出不同的温度偏好和迁移率，这些支流由不同的尾水温度和地理距离隔开。这是对人类造成的运动热障碍如何影响零散支流鱼类种群遗传结构的首次研究，对于集中今后的管理和养护努力以改善尾水环境中暖水支流的热连通性以确保暖水鱼类种群的长期持久性具有重要意义。

The great utility of running waters has resulted in the extensive exploitation of streams and rivers throughout the world, a process greatly facilitated by the construction of hundreds of thousands of dams globally. It is well established that dams have a fragmenting effect on the landscape by blocking the movement of individuals between essential habitats required to complete their life cycle (e.g., salmon species in the Pacific Northwest). Moreover, many dams throughout the world have dramatically modified downstream environments by selectively releasing cold water from reservoirs in order to establish productive trout fisheries in the tailwater reaches of the dammed river. Our recent research in southeastern United States shows that the conversion from warmwater to coldwater habitats can result in significant losses to fish populations in the tailwaters, whereas the adjoining, warmwater tributaries provide thermal refugia and contain extremely dense and diverse fish assemblages. These results led to the hypothesis that coldwater-release dams may have an additional fragmenting effect by restricting fish movement through the cold tailwaters, which over time could lead to the genetic differentiation of the tributary fish populations. We address this hypothesis by examining the genetic structure of 3 fish species that exhibit different thermal preferences and mobility's in a series of tributaries that are separated by different tailwater temperatures and geographic distances. This is the first examination of how human-induced thermal barriers to movement may shape the genetic structure of fish populations in fragmented tributaries, and has important implications for focusing future management and conservation efforts aimed at improving the thermal connectivity of warmwater tributaries in tailwater environments in order to ensure the long-term persistence of warmwater fish assemblages.