Natural Hybridization between a Sympatric Pair of Hawaiian Drosophila

Natural interspecific hybrids between two closely related species of Hawaiian Drosophila, heteroneura and silvestris, have been collected from the Kahuku Ranch area on the Island of Hawaii. Despite full fertility of both sexes of these hybrid specimens, hybridization is apparently not extensive. Investigations of the degree of introgression between these two species and of environmental factors which might contribute to the breakdown of isolating mechanisms are continuing.