Data from: A test for environmental effects on behavioral isolation in two species of killifish

Behavioral isolation is a common and potent mechanism of reproductive isolation. Determining the extent to which behavioral isolation varies with environmental conditions is critical to understanding speciation and the maintenance of species boundaries. Here, we tested the effect of salinity on behavioral isolation (female species recognition, male-male competition, male species recognition) between two closely related killifish (Lucania goodei and L. parva) that differ in salinity tolerance. We performed no-choice assays and behavioral trials where males could compete and court females in fresh water (0 ppt) and brackish water (15 ppt). We found high levels of behavioral isolation that did not vary as a function of salinity. In behavioral trials, male species recognition of females was strong and asymmetric between the two species. Lucania goodei males preferred conspecifics and rarely courted or mated with L. parva females. Lucania parva males preferred conspecifics but readily courted and mated with L. goodei females. This asymmetry matches previously documented asymmetries in hybrid offspring fitness. Crosses between L. parva males and L. goodei females produce fully viable/fertile hybrids, but crosses between L. goodei males and L. parva females produce males with reduced fertility. Hence, behavioral isolation may have evolved in part due to reinforcement.行为隔离（behavioral isolation）是生殖隔离（reproductive isolation）中常见且高效的机制。明确行为隔离随环境条件变化的程度，对于理解物种形成与物种边界的维持至关重要。本研究针对盐度耐受性存在差异的两种近缘鳉鱼（killifish）——卢奇鳉（Lucania goodei）和帕瓦鳉（L. parva）——开展实验，检验盐度对其行为隔离（包括雌性物种识别、雄性间竞争、雄性物种识别）的影响。我们分别在淡水（0 ppt）与咸淡水（15 ppt）环境中开展了无选择实验与行为试验，允许雄性个体间发生竞争并向雌性求偶。研究结果显示，两种鳉鱼间存在高强度的行为隔离，且该隔离程度并未随盐度发生显著变化。在行为试验中，雄性对雌性的物种识别表现强烈，且在两个物种间呈现不对称性：卢奇鳉雄性偏好同种雌性，极少向帕瓦鳉雌性求偶或与之交配；而帕瓦鳉雄性同样偏好同种雌性，但却会主动向卢奇鳉雌性求偶并与之交配。这种不对称性与此前已报道的杂交后代适合度不对称性相一致：帕瓦鳉雄性与卢奇鳉雌性的杂交可产生完全存活且可育的后代，而卢奇鳉雄性与帕瓦鳉雌性的杂交则会产生育性降低的雄性后代。因此，行为隔离的演化可能部分源于强化选择。