PHYLOGENY OF THE ISLAND POPULATIONS OF THE HAWAIIAN DROSOPHILA-GRIMSHAWI COMPLEX - EVIDENCE FROM COMBINED DATA

The picture-winged species Drosophila grimshawi is unique among Hawaii an Drosophila in its wide geographic range, having populations on seve ral islands of the Hawaiian archipelago. This distribution contrasts w ith the pattern of single-island endemism observed in most of the pict ure-winged group; significantly, it does not concur with predictions o f the founder theory, where speciation is the typical outcome of found er events involving colonization of a new island. To examine this anom alous situation, we have taken a phylogenetic approach in an attempt t o resolve the relationships among taxa and decipher the most probable colonization scenario. We have obtained both morphological and molecul ar data for all the D. grimshawi populations as well as the closely re lated species D. pullipes, and two outgroup species, using scanning el ectron microscopy to score ultrastructural features of the chorion or eggshell, and PCR amplification and nucleotide sequencing to acquire s equence data on Yp1, one of the three Yolk protein genes. In addition, we have used available data on Yolk Protein electrophoretic pattern a nd jousting, oviposition, and mating behavioral characters. Analyses o f these data sets, either individually or in combination, indicate tha t there are two separate and ecologically distinct clades within this species complex. One clade includes the Kauai and Oahu populations of grimshawi, as well as the closely related species D. pullipes from Haw aii, all of which are classified as ecological specialists with respec t to their oviposition and breeding substrate. The other clade include s all the ecologically generalist grimshawi populations of the Maui Nu i island complex. The phylogenetic results do not concur with the prev iously proposed hypothesis that D. pullipes originated from a founder derived from the Maul Nui complex and further suggest that these taxa are in need of taxonomic revision. (C) 1997 Academic Press.