Data from: The ecology of an adaptive radiation of three-spined stickleback from North Uist, Scotland

There has been a large focus on the genetics of traits involved in adaptation, but knowledge of the environmental variables leading to adaptive changes is surprisingly poor. Combined use of environmental data with morphological and genomic data should allow us to understand the extent to which patterns of phenotypic and genetic diversity within a species can be explained by the structure of the environment. Here, we analyse the variation of populations of three-spined stickleback from 27 freshwater lakes on North Uist, Scotland, that vary greatly in their environment, to understand how environmental and genetic constraints contribute to phenotypic divergence. We collected 35 individuals per population and 30 abiotic and biotic environmental parameters to characterize variation across lakes and analyse phenotype–environment associations. Additionally, we used RAD sequencing to estimate the genetic relationships among a subset of these populations. We found a large amount of phenotypic variation among populations, most prominently in armour and spine traits. Despite large variation in the abiotic environment, namely in ion composition, depth and dissolved organic Carbon, more phenotypic variation was explained by the biotic variables (presence of predators and density of predator and competitors), than by associated abiotic variables. Genetic structure among populations was partly geographic, with closer populations being more similar. Altogether, our results suggest that differences in body shape among stickleback populations are the result of both canalized genetic and plastic responses to environmental factors, which shape fish morphology in a predictable direction regardless of their genetic starting point.

学界对适应性相关性状的遗传学机制已有大量研究，但对于驱动适应性演化的环境变量的认知却意外匮乏。将环境数据与形态学、基因组学数据整合分析，可帮助我们阐明：物种内的表型与遗传多样性格局，在多大程度上可由环境结构予以解释。本研究针对苏格兰北尤伊斯特岛27个环境差异显著的淡水湖中的三刺棘鱼（three-spined stickleback）种群展开变异分析，以探究环境与遗传限制如何共同推动表型分化。我们从每个种群中采集35尾个体，并测定30项非生物与生物环境参数，以刻画不同湖泊间的环境变异特征，并分析表型与环境的关联。此外，我们通过RAD测序（RAD sequencing）估算了其中部分种群间的遗传亲缘关系。研究发现种群间存在大量表型变异，其中以护甲与棘突性状的差异最为显著。尽管非生物环境（尤其是离子组成、水深与溶解性有机碳）存在显著变异，但相较于非生物变量，生物变量（捕食者存在情况、捕食者与竞争者的密度）对表型变异的解释度更高。种群间的遗传结构存在一定的地理模式：地理距离越近的种群，遗传相似性越高。综合来看，本研究结果表明，棘鱼种群间的体型差异是渠化遗传响应与表型可塑性响应共同作用于环境因素的结果——这两类响应会以可预测的方向塑造鱼类形态，且不受种群初始遗传背景的影响。