Behavioral isolation, test designs, and Kaneshiro's hypothesis

Studies of the planitibia group of the Hawaiian Drosophila inspired the controversial hypothesis that the direction of evolution can be inferred by examining the direction of asymmetrical behavioral reproductive isolation. One criticism of this hypothesis is based on the methods that were used to develop it: the sign and magnitude of the indexes of behavioral reproductive isolation may vary with the procedures employed to measure them. We evaluated this criticism by applying three common methods used for measuring behavioral reproductive isolation to the species D. heteroneura and D. silvestris. These are the species that were used in the original development of the behavioral isolation hypothesis. The methods were female choice, male choice, and multiple choice. We found a similar direction of asymmetry for all three testing methods in the pairing of D. silvestris and D. heteroneura. In contrast, the pairing between two populations of D. silvestris did not give a consistent direction of asymmetry. Thus, different methods for testing the direction of behavioral reproductive isolation give similar results at the interspecific level but are inconsistent at the intraspecific level.