R. C. L. Perkins' Legacy to Evolutionary Research on Hawaiian Drosophilidae (Diptera)l

R. C. L. Perkins' influence on evolutionary research on the Hawaiian Drosophilidae is presented. His observations of the bizarre secondary sexual structures in this group led evolutionary biologists to focus research on the role of sexual selection in speciation and the evolutionary processes responsible for the proliferation of Drosophila species in the native Hawaiian fauna. A review of early taxonomic treatment of the group and some of the ecological novelties of the group are discussed. A better understanding of the genetics, ecology, behavior, morphology, etc. resulted in a revision of the generic concepts of the group, and subsequent phylogenetic studies using modem tools of molecular biology have confirmed the monophyletic relationships among the species in this group. FROM 1893 TO 1897, R. C. L. Perkins conducted an extensive survey of Hawai'i's insect fauna. The results of Perkins' collections and the detailed field notes he recorded for the specimens including host records provided the basis for his publication in the Fauna Hawaiiensis (1913). Perkins' efforts and careful record keeping provide extremely valuable baseline information that we can use to infer relative abundance of the populations as well as the quality of the habitat in which these species lived a century ago. It will enable us to compare estimates of diversity in the insect fauna with surveys conducted during later decades especially in two groups that Perkins surveyed extensively: the Megalagrion damselflies and the platynine carabid beetles. Although Perkins focused much of his efforts in collecting many of the groups of insects in Hawai'i, there were some groups that presented logistical problems for him primarily because of the difficult conditions fieldwork presented to entomologists of his time. It was clear that Perkins was "uncomfortable" with collecting dipteran species in the Hawaiian fauna. In his introduction to Fauna Hawaiiensis, he commented that"... the minute and obscure Diptera, 1 This is contribution no. 1996-020 of the Hawai'i Biological Survey. Manuscript accepted 3 February 1997. 2 Center for Conservation Research and Training, University of Hawai 'i at Manoa, 3050 Maile Way, Gilmore 409, Honolulu, Hawai'i 96822. the endemic species largely consisting of small Dolichopodidae, which shrink and distort on drying, and of infinite numbers of Drosophilidae, many of these also becoming distorted, have been little collected" (Perkins 1913). He had difficulty in preserving these soft-bodied insects under the harsh conditions he faced in the field and therefore he did not make a special effort to collect dipteran species as he did some of the other major orders of insects. Nevertheless, based on what he saw of the drosophilid fauna in Hawai'i, he made the following comments: "Drosophila is represented by an assemblage of species, exhibiting great diversity in structure and appearance. . . . At present these insects, many of which are obscure and minute forms, have been very imperfectly collected. To make an approximately complete collection and thorough study of the Hawaiian species would require the devotion of many years of special work. Not less than 250 species must exist in the islands, and double that number may very probably occur" (Perkins 1913:189). Perkins recognized the tremendous diversity in the Drosophilidae, and his assessment of the group was echoed by Elwood C. Zimmerman, another entomologist with considerable experience in the Hawaiian fauna, who wrote a passionate plea to geneticists and evolutionists about the remarkable drosophilid fauna in Hawai'i and the opportunity to conduct "advanced research" on this group of flies. He