Responses to simulated winter conditions differ between threespine stickleback ecotypes

Abiotic factors can act as barriers to colonization and drive local adaptation. During colonization, organisms may cope with changes in abiotic factors using existing phenotypic plasticity, but the role of phenotypic plasticity in assisting or hindering the process of local adaptation remains unclear. To address these questions, we explore the role of winter conditions in driving divergence during freshwater colonization and the effects of plasticity on local adaptation in ancestral marine and derived freshwater ecotypes of threespine stickleback (Gasterosteus aculeatus). We found that freshwater-resident stickleback had greater tolerance of acute exposure to low temperatures than marine stickleback, but these differences were abolished after acclimation to simulated winter conditions (9L:15D photoperiod at 4°C). Plasma chloride levels differed between the ecotypes, but showed a similar degree of plasticity between ecotypes. Gene expression of the epithelial calcium channel (ECaC) diffe...非生物因子可作为定殖障碍并驱动局部适应。在定殖过程中，生物体可借助自身已有的表型可塑性（phenotypic plasticity）应对非生物因子的变化，但表型可塑性在辅助或阻碍局部适应进程中所发挥的作用仍未明确。为解答上述疑问，我们以三刺鱼（Gasterosteus aculeatus）的祖先海洋种群与衍生淡水生态型为研究对象，探究冬季条件在淡水定殖过程中驱动分化的作用，以及可塑性对局部适应的影响。我们发现，淡水定居型三刺鱼对低温急性暴露的耐受性高于海洋三刺鱼，但在经过模拟冬季条件（9L:15D光周期、4℃）驯化后，上述差异完全消失。两种生态型的血浆氯离子水平存在差异，但二者的表型可塑性程度相近。上皮钙通道（epithelial calcium channel, ECaC）的基因表达水平差异……