Ecology and Evolution of Drosophila ambochila, A Rare Picture-Winged Species Endemic to the Wai'anae Range of O'ahu, Hawaiian Islands

Abstract

The rare O'ahu picture-winged fly Drosophila ambochila Hardy & Kaneshiro is endemic to two windward ravines in the Wai'anae Mountains that harbor its host plant. Drosophila ambochila is an ecological specialist that breeds on Pisonia stems and trunks in an intermediate stage of decay. By providing field-collected females with suitable substrate material, we have been able to observe the oviposition behavior of this species in the laboratory and obtain F 1 larvae. In nature, females oviposit each batch of mature eggs ("'4050) in a single cluster, by repeatedly inserting their long ovipositor into the same crack or beetle hole in the decaying Pisonia bark. Ovipositor, ovary, and egg morphology are characteristic of bark-breeding Hawaiian Drosophila, but SEM studies revealed a distinctive chorionic ultrastructure for the eggs of this species. Larval salivary chromosome analyses indicated that the O'ahu D. ambochila is most closely related to D. alsophila from the island of Hawai'i and have helped to resolve the phylogenetic relationships among six of the nine species belonging to the vesciseta subgroup of the glabriapex species group.