Data from: Differences in rheotactic responses contribute to divergent habitat use between parapatric lake and stream threespine stickleback

Migration among populations is widely thought to undermine adaptive divergence, assuming gene flow arises from random movement of individuals. If individuals instead differ in dispersal behavior, phenotype-dependent dispersal can reduce the effective rate of gene flow or even facilitae divergence. For example, parapatric populations of lake and stream stickleback tend to actively avoid dispersing into the adjoining habitat.. However, the behavioral basis of this non-random dispersal was previously unknown. Here we show that lake and stream stickleback exhibit divergent rheotactic responses (behavioral response to currents). During the breeding season, wild-caught inlet stream stickleback were better than lake fish at maintaining position in currents, faced upstream more, and spent more time in low-current areas. As a result, stream fish expended significantly less energy in currents than did lake fish. These divergent rheotactic responses likely contribute to divergent habitat use by lake and stream stickleback. Although rheotactic differences were absent in non-breeding fish, divergent behavior of breeding-season fish may suffice for assortative mating by breeding location. The resulting reproductive isolation between lake and stream fish may explain the fine-scale evolutionary differentiation in parapatric stickleback populations.种群间的迁徙普遍被认为会破坏适应性分化，其前提假设是基因流源于个体的随机移动。若个体的扩散行为存在差异，依赖于表型的扩散便可能降低基因流的有效速率，甚至促进分化。例如，湖泊与溪流的邻域（parapatric）棘鱼种群往往会主动避免扩散至相邻生境。不过此前学界对这种非随机扩散的行为基础尚不清楚。本研究表明，湖泊与溪流棘鱼表现出趋流反应（rheotactic responses，对水流的行为响应）的分化。在繁殖季节，野外捕获的入水口溪流棘鱼在水流中维持自身位置的能力优于湖泊种群个体，它们更常朝向水流上游，且更多时间停留于低流速区域。因此，溪流棘鱼在水流中消耗的能量显著低于湖泊种群个体。这些趋流反应的分化或许是导致湖泊与溪流棘鱼生境使用分化的关键原因。尽管非繁殖个体未表现出趋流行为差异，但繁殖季节个体的分化行为足以促成基于繁殖地点的选型交配。由此形成的湖泊与溪流棘鱼间的生殖隔离，或许可以解释邻域棘鱼种群的精细尺度进化分化。