Female preferences for conspecific males indicate reproductive isolation between sympatric Labeotropheus Ahl from Lake Malaŵi

Abstract In sexually reproducing taxa, reproductive isolation is key to speciation. Given the speed with which behavioral reproductive isolation evolves, this form of isolation is of particular importance to rapidly evolving species. Here we examine behavioral reproductive isolation in a sympatric, congeneric pair of rock‐dwelling cichlids from Lake Malaŵi, testing the hypothesis that females should prefer conspecific males. We used a pair of Labeotropheus, L. fuelleborni Ahl and L. trewavasae Fryer, from the Chidunga Rocks in southwestern Lake Malaŵi, to test this hypothesis, with the prediction that females would approach conspecific males more frequently than they would heterospecific males. When given a choice between a male L. fuelleborni and L. trewavasae, we found that females did approach males of their own species more frequently than males of the opposite species, and that differences in length and the number of eggspots on the anal fin between the stimulus males had no effect on a female's choice. These results are consistent with behavioral reproductive isolation between these sympatric species, and add further support to the hypothesis that sexual selection played a key role in the speciation of cichlid fishes from Lake Malaŵi.