Ecological specialization of HawaiianDrosophila : Habitat selection in Kipuka Puaulu

Abstract

TheDrosophila community of Kipuka Puaulu, Hawaii Volcanoes National Park, was studied by field measurements and laboratory experiments. Phototactic responses were related to oviposition substrates forD. mimica andD. imparisetae, and were shown to reinforce substrate attractiveness. Both species were associated with rottingSapindus fruit, butD. imparisetae, less light tolerant thanD. mimica, was found in deeper shade. Individuals of a third species,D. kambysellisi, were strongly attracted to substratePisonia leaves. The attraction was strong enough to override strong positive phototaxis. The significance of this behavior was related to the adaptive strategy of the species. The sibling species,D. mimica andD. kambysellisi, utilized different substrates and were strongly separated spatially. Differences in substrates and mobility were related to the "grain size" of their environment. Males ofD. kambysellisi andD. imparisetae are located in leking sites above their respective females during the day. This behavior parallels the relatively greater light tolerance of males than of females. The same light response dimorphism inD. mimica is not accompanied by leking behavior, since they mate at night or in greatly subdued light.