Data from: Genetic population structure in prickly sculpin (Cottus asper) reflects isolation by environment between two life history ecotypes

Life-history transitions have evolved repeatedly in numerous taxa, although the ecological and evolutionary conditions favouring such transitions in the presence of gene flow remain poorly understood. The present study aimed to disentangle the effects of isolation-by-distance and isolation-by-environment on genetic differentiation between two sympatric life-history ecotypes. Using 14 microsatellite loci, we first characterized amphidromous and freshwater groups of Cottus asper in a high gene flow setting in the Lower Fraser River system (south-western British Columbia, Canada) to test for the effects of habitat and geographical distance on the distribution of life-history ecotypes. Within the main river channel, no genetic differentiation was found, whereas tributaries even close to the estuary were genetically differentiated. Partial mantel tests confirmed that genetic differentiation between river tributaries and the main channel was independent from geographical distance, with distance-scaled migration rates indicating reduced gene flow from the main channel into the tributaries. Our results suggest that isolation-by-environment can play an important role for the early stage of life-history transitions, and may promote differentiation among life-history ecotypes despite the presence of gene flow.

生活史转变在众多生物类群中多次独立演化，但在基因流（gene flow）存在的前提下，促进这类转变发生的生态与进化条件仍未得到充分阐明。本研究旨在厘清距离隔离（isolation-by-distance）与环境隔离（isolation-by-environment）对两种同域分布生活史生态型间遗传分化的相对影响。我们利用14个微卫星位点（microsatellite loci），首先在加拿大不列颠哥伦比亚省西南部弗雷泽河下游水系这一高基因流环境中，对糙杜父鱼（Cottus asper）的溯河洄游型与淡水定居型类群进行了遗传分型，以检验生境与地理距离对生活史生态型分布的影响。在主河道内未检测到遗传分化，而即便距离河口较近的支流也存在显著遗传分化。偏曼特尔检验（partial mantel test）证实，河流支流与主河道间的遗传分化与地理距离无关，距离标度迁移率显示主河道向支流的基因流显著降低。本研究结果表明，环境隔离在生活史转变的早期阶段可发挥关键作用，即便存在基因流，也可能推动生活史生态型间的遗传分化。