A Hierarchical View of the Hawaiian Drosophilidae (Diptera)l

As the pioneer natural historian of the Hawaiian entomofauna, R. C. L. Perkins showed a keen interest in the Diptera, in general, and the Drosophilidae, in particular. Perkins described and named two of the most charismatic of the Hawaiian picture-winged drosophilid flies: Idiomyia heteroneura and I. silvestris. These two species are part of a chromosomally homosequential quartet of species that have garnered the attention of research programs of numerous biologists. In this paper we review the evidence on the phylogenetic relationships among the flies in this quartet and suggest some guidelines for the inference of phylogeny within this quartet of species as further data accumulate. Perkins was also one of the first to recognize the extent of diversity of the Drosophilidae within and among islands of the archipelago. Several more-recent research programs have concentrated on understanding the evolutionary history of this diversification. Two questions regarding the high degree of diversity of these flies are discussed from a systematic perspective in this paper. The first concerns the relationships of the major species groups assemblages of the Hawaiian drosophilids. The second focuses on the origin of the Hawaiian drosophiloid and scaptomyzoid flies. R. C. L. PERKINS RECOGNIZED that of all of the Diptera in Hawai'i, the Drosophilidae were unique in their degree of differentiation, speciation, and complex patterns of geographical distribution. Understanding this remarkable diversity and distribution has been a major research goal of drosophilists following Perkins' pioneering efforts. Over the past century, experimental approaches used to examine these flies have also been diverse, ranging from taxonomic studies to molecular biology. Phylogenetic relationships among the Drosophilidae in Hawai'i have been investigated at many hierarchical levels. A detailed understanding of the systematics of these flies can aid greatly in advancing our conceptions of their diversity and distribution and provide a framework for understanding the origin of evolutionary novelty from the molecular to the phenotypic level. Much of the recent systematic work on the J Manuscript accepted 3 February 1997. 2 Department ofEntomology, American Museum of Natural History, 79th Street at Central Park West, New York, New York 10024. 3 Department of Biology, Yale University, New Haven, Connecticut 06511. 4 Department of Biology, New York University, New York, New York 10003. Hawaiian Drosophilidae has centered on higherlevel relationships (Takada 1966, Throckmorton 1966, Kaneshiro 1976). In particular, systematists are interested in identifying the continental group that gave rise to the Hawaiian radiation and whether the two major groups of Drosophilidae found in the archipelago (drosophiloids and scaptomyzoids) arose as the result of one or two colonization events (Takada 1966, Throckmorton 1966, Stalker 1972). Systematic studies have also attempted to address the issue of the relationships of the various morphologically distinct species groups among the endemic drosophilids (Throckmorton 1966). In addition, the application of polytene chromosome analysis has advanced our understanding of species relationships within one of the species groups: the picture-winged Drosophila (Carson et al. 1967, Carson and Kaneshiro 1976). Shared patterns of banding reflecting historical inversions in polytene chromosomes were used extensively to examine the relationships of almost 100 picturewinged species. Allozyme studies, immunological studies, DNA-DNA hybridization, new morphological studies, and DNA sequence studies have subsequently been used to examine these older systematic questions as well as newer