The Hawaiian Drosophilidae are a lineage of flies within the genus Drosophila. This monophyletic clade includes all of the endemic Hawaiian Drosophila and all members of the genus Scaptomyza, which contains both Hawaiian and non-Hawaiian species. The Hawaiian Drosophilidae are descended from a common ancestor estimated to have lived 25 million years ago. Species of Hawaiian Drosophilidae flies have been studied as models of speciation and behavioral evolution. Along with other members of the native Hawaiian ecosystem, the conservations status of many species of Hawaiian Drosophilidae is threatened by habitat loss and introduced predators, among other factors.
Diversity
There are an estimated 1,000 species of Hawaiian Drosophilidae. 689 species have been described, including 273 species in the genus Scaptomyza, of which 148 are endemic to the Hawaiian archipelago, and 416 Hawaiian endemic species in the genus Drosophila. Within the Hawaiian Drosophila there are several major groups, including the modified-mouthpart, modified-tarsus, and antopocerus species groups, and the picture-wing clade.
Scaptomyza
The genus Scaptomyza, which contains both Hawaiian and non-Hawaiian species, is the sister lineage to the Hawaiian Drosophila, and Hawaiian species in this genus are often included when speaking about the Hawaiian Drosophila generally. The Hawaiian and non-Hawaiian distribution of Scaptomyza can be explained as either the result of multiple colonizations of Hawaii, or as the result of one colonization by the common ancestor of Scaptomyza and Hawaiian Drosophila, followed by several migrations back to continents. Scaptomyza is one of several genera that are currently nested within the genus Drosophila, rendering it paraphyletic.
Hawaiian Drosophila
Picture-wing, nudidrosophila, ateledrosophila (PNA) clade
The picture-wing clade of Hawaiian Drosophila is named for the intricate patterns of melanin pigment on their wings. This clade includes the grimshawi, planitibia, and adiastola species groups, among others.
Research on the taxonomy and biology of picture-wing flies in the 1970's led to the description of 105 species, with several more described in the decades since. More recent studies on variation in wing patterns has led to the generation of a database devoted solely to wing diversity in the Hawaiian Drosophila lineage. These flies have also been extensively studied for their courtship behavior, potential for hybridization between species, and larval ecology. Many species of picture-wing flies breed in rotting bark and stems.
Antopocerus, modified-tarsus, ciliated-tarsus (AMC) clade
The antopocerus species group includes 15 species of flies, notable for their large adult body size and egg size, as well as the prominent antennae on males. Antopocerus was previously considered as a distinct genus, before being sunk into the genus Drosophila based on their phylogenetic position within other Hawaiian lineages. Species of antopocerus flies have been described from the islands of Maui, Molokai, Lanai, Hawaii, and one species from Oahu.
The modified-tarsus species group is so named because of the variation in the shape and structure of front tarsi of males. These tarsal modifications include flattened, spoon-shaped structures, elongated cilia, and clusters of bristles, and are thought to be used in mating displays. Antopocerus and modified-tarsus flies largely breed in rotting leaves.
Modified-mouthparts species group
The modified-mouthparts species group is named for the divergent forms of labellar structures relative to other Drosophila species. This large group of flies has received relatively less study, in part due to their rarity and because many species are not attracted to typical Drosophila baits. These flies show a remarkable diversity in breeding ecology, with the majority of species using more than one host family for larval feeding. There are more than 100 described species of modified-mouthparts flies, distributed throughout all major Hawaiian islands.
Haleakalae species group
Haleakalae species are typically small, slender, and with shiny black bodies. Rearing records indicate that members of this group breed exclusively on fungus. There are more than 50 described species of Haleakalae flies, distributed throughout all major Hawaiian islands. These species are characterized by their simple courtship displays, relative to some picture-wing species, and the short filaments on their eggs. Some species also have a black rim on the labellum.