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 courte...