Zaprionus

The genus Zaprionus belongs to the family fruit fly Drosophilidae and is positioned within the paraphyletic genus Drosophila. All species are easily recognized by the white longitudinal stripes across the head and thorax. The genus is subdivided in two subgenera, based on the presence of an even (subgenus Zaprionus) or odd (subgenus Anaprionus) number of white stripes. The species of the genus can be found in African and Southern Asia. One species, Zaprionus indianus, has invaded the New World. All species in the genus Zaprionus are easily identified by the longitudinal white stripes bordered by black stripes running across the top of the head and thorax. Species of the subgenus Zaprionus have 4 or 6 white stripes while the species of the subgenus Anaprionus have 5 or 7 white stripes. The general body color varies across species from yellowish to dark brown. Several species of the subgenus Zaprionus have one or more stout and sometimes composite spines on the forelegs. The characteristic black and white 'zebra' stripes of this genus have two different origins. In the simplest form, the white stripes are caused by an absence of the pigment in the cuticle. This mechanism is found in species of the subgenus Anaprionus. The absence of pigmentation also occurs in the species of the subgenus Zaprionus, probably complemented by a separate mechanism. In these species, the white stripes contain many long and bent trichomes (fine outgrowths) that have a groove and contain two cavities, polarizing the light. The black stripes are caused by pigmentation. Members of this genus can be found in the tropics of most continents. The species of the subgenus Zaprionus are found primarily in Africa, while the species of the subgenus Anaprionus are found in Southeast Asia. Two species, Zaprionus ghesquierei and Zaprionus indianus have expanded their range in recent times. Zaprionus ghesquierei has invaded Hawaiʻi, while Zaprionus indianus has expanded its range though the Middle East towards India and more recently crossed the Atlantic Ocean and colonized both South and North America. Zaprionus species are found in a wide array of habitats from semi-deserts to the tropical rain forest. Most species breed on fruits, flowers or decaying tree trunks. The genus Zaprionus was described in 1902 by Daniel William Coquillett. He considered the genus closely related to the genus Drosophila. Molecular studies have confirmed this relationship, and the genus Zaprionus is positioned within the paraphyletic genus Drosophila. Within the genus, species with an odd number of stripes are assigned to the subgenus Anaprionus, while the species with an even number of stripes are assigned to the subgenus Zaprionus. Species within the subgenus Zaprionus were traditionally subdivided in two species groups, armatus and inermis, based on the presence or absence of special spines on the forelegs. The armatus species group was further subdivided into three species subgroups based on the type of spines. The species of the armatus species subgroup have several normal spines. The single spine on forelegs of the species of the tuberculatus species subgroup consists of a large spine positioned on a tubercle with a smaller spine near the base of the spine. Finally, the species of the vittiger species subgroup had a row of composite spines generally positioned on small tubercles. Recent molecular studies have shown that this subdivision of the Zaprionus subgenus is incorrect. The ornamentation has evolved multiple times and is not a reliable characteristic for classification. The tuberculatus species group is now part of the group lacking ornamentation (inermis), and the closet relatives of species with a large composite spines are closely related to species without such a spine. The vittiger species subgroup is now a species group and a new species group, neglectus, has been erected for one species placed at the root of the Zaprionus subgenus.