Niche separation of African Lissocephala within the Ficus Drosophilid community

Summary

The oviposition sites and larval cycle of the African species of Lissocephala, the most primitive genus of Drosophilidae, are described here for the first time. The genus Lissocephala has achieved a novel adaptive direction in the Ethiopian region. All known African species are strictly specialized on Ficus. This species diversity suggests that ecological transfer to Ficus preceded the Lissocephala radiation. Lissocephala larvae breed inside immature figs. The eggs are laid in or near the fig ostiole. First instar larvae enter the fig receptacle though the ostiolar entrance is constantly closed by firmly imbricating bracts. Third instar larvae leave the fig by crawling out between the ostiolar bracts, and drop to the soil where they pupate. Thus Lissocephala species larvae breed inside a sheltered microhabitat, since the numerous other sympatric sycophagous Drosophilids do not have the ability to colonize immature figs. Other groups of Drosophilid species breed successively on the ripening exocarp of the fig following the successive microbial states of the fig. The possibility of coevolution of Lissocephala species, Ficus species and pollinator fig wasp species is discussed. Selection for avoidance of competition increased Lissocephala species' efficiency in exploiting unutilized immature figs and then provided a conspicuous niche separation which contributed to species packing on figs.