Tracing ancestry with chromosomal sequences.

Most of the large Drosophila species of Hawaii are single-island endemics. Chromosomal sequences show that species at the new end of the archipelago have been derived stepwise from ancestral populations on older islands. The oldest high island has an endemic species with sequences that match some in the Nearctic-Palearctic robusta species group. Colonization from a continent by long-distance dispersal seems a likely origin for the Hawaiian drosophilids. Telmatogeton, a worldwide genus of marine midges, has five Hawaiian species inhabiting freshwater streams. Chromosomal sequences of a marine species in Hawaiian waters match the freshwater forms, indicating colonization from the ocean.