Data from: Physiological and genomic signatures of evolutionary thermal adaptation in redband trout from extreme climates

Temperature is a master environmental factor that limits the geographical distribution of species, especially in ectotherms. To address challenges in biodiversity conservation under ongoing climate change, it is essential to characterize relevant functional limitations and adaptive genomic content at population and species levels. Here, we present evidence for adaptive divergence in cardiac function and genomic regions in redband trout (Oncorhynchus mykiss gairdneri) populations from desert and montane streams. Cardiac phenotypes of individual fish were measured in the field with a custom-built electrocardiogram apparatus. Maximum heart rate and its rate limiting temperature during acute warming were significantly higher in fish that have evolved in the extreme of a desert climate compared to a montane climate. Association mapping with 526,301 single nucleotide polymorphisms (SNPs) across the genome revealed signatures of thermal selection both within and among ecotypes. Among desert and montane populations, 413 SNPs were identified as putative outliers under natural selection and 20 of these loci showed significant association with average summer water temperatures among populations. Phenotypes for cardiac performance were variable within each ecotype and 207 genomic regions were strongly associated with either maximum heart rate or rate limiting temperatures among individuals. Annotation of significant loci provided candidate genes that underlie thermal adaptation, including pathways associated with cardiac function (IRX5, CASQ1, CAC1D and TITIN), neuroendocrine system (GPR17 and NOS) and stress response (SERPH). By integrating comparative physiology and population genomics, results here advance our knowledge on evolutionary processes of thermal adaptation in aquatic ectotherms.温度是制约物种地理分布的核心环境因子，对于变温动物（ectotherm）而言尤为如此。为应对当前气候变化下生物多样性保护所面临的挑战，在种群与物种层面解析相关功能限制与适应性基因组特征至关重要。本研究针对来自荒漠与山地溪流的红带鳟（Oncorhynchus mykiss gairdneri）种群，揭示了其心脏功能与基因组区域的适应性分化证据。研究人员使用定制搭建的心电图设备，在野外对个体鱼类的心脏表型进行了测定。相较于适应山地气候的个体，在极端荒漠气候环境中演化的鱼类，其急性升温过程中的最大心率及心率限制温度显著更高。通过对全基因组范围内526301个单核苷酸多态性（single nucleotide polymorphisms, SNPs）进行关联定位分析，研究团队在生态型内部及生态型之间均检测到了热选择的信号。在荒漠与山地种群中，共有413个SNPs被鉴定为自然选择下的潜在离群位点，其中20个位点与种群间的夏季平均水温呈显著关联。各生态型内部的心脏功能表型存在变异，且在个体层面，共有207个基因组区域与最大心率或心率限制温度呈显著关联。对显著位点的注释结果筛选出了一系列热适应相关的候选基因，包括与心脏功能相关的通路基因（IRX5、CASQ1、CAC1D及TITIN）、神经内分泌系统相关基因（GPR17与NOS）以及应激反应相关基因（SERPH）。本研究通过整合比较生理学与种群基因组学方法，加深了我们对水生变温动物热适应演化过程的认知。