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（ectotherms）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。本研究针对来自沙漠溪流与山地溪流的红带鳟（Oncorhynchus mykiss gairdneri）种群，提供了其心脏功能与基因组区域存在适应性分化的证据。研究团队采用定制化心电图设备，在野外环境下测定了单尾个体的心脏表型。相较于山地环境种群，在极端沙漠气候下演化的个体，其急性升温过程中的最大心率及心率限制温度均显著更高。通过对全基因组范围内526301个单核苷酸多态性（SNPs）进行关联定位，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。在沙漠与山地种群中，共有413个SNPs被鉴定为自然选择下的潜在异常位点，其中20个基因座与种群间夏季平均水温存在显著关联。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存在显著关联。对显著位点的注释筛选出了参与热适应的候选基因，涵盖与心脏功能相关的通路（IRX5、CASQ1、CAC1D及TITIN）、神经内分泌系统（GPR17与NOS）以及应激反应通路（SERPH）。本研究通过整合比较生理学与种群基因组学方法，深化了我们对水生变温动物热适应演化过程的认知。