Family DROSOPHILIDAE Rondani, 1856

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Introduction

The importance of the Drosophila (Drosophilidae) model for understanding basic biological mechanisms, sequencing the human genome and ultimately improving human health is ever more evident. The combination of powerful genomic and proteomic technologies built on a century of genetic research on Drosophila makes research on this group of species unparalleled in biological science. Twelve complete Drosophila genomes were published recently (Drosophila 12 Genomes Consortium 2007) and interest in expanding genetic information to related taxa is increasing. Maximizing the benefits of these developments depends crucially on sound taxonomy and the correct application of species' names.

The family Drosophilidae has 73 genera worldwide, and is represented in Australia by 35. Five genera Balara, Bialba, Collessia, Crincosia and Poliocephala are endemic and four are monotypic. A sixth genus, Tambourella, is represented by three species, the Australian type species and two others from New Guinea. About 50 Australian species are known but undescribed, and many more probably await discovery in the Wet Tropics. In recent years new taxa have emerged by fruit-baiting at different elevations in sclerophyll forests and from Malaise and light traps in semi-arid parts of the continent. The parts of the fauna associated with insect exudates, animal excreta, sap fluxes, and fermenting nectaries (e.g. Acletoxenus, Amiota, Cacoxenus, Gitona spp.) have been very poorly sampled. There are scattered records worldwide of drosophilid larvae preying on, or feeding near, aphids, mealy bugs, white fly, spider eggs, terrestrial crabs (on Christmas Island, qv), partially submerged simuliid larvae and bee larvae. Rainforest canopies have been poorly surveyed in Australasia, but have yielded enormous drosophilid diversity in the Neotropical Region.

Drosophilids are unlike other acalyptrate flies because they have a proclinate and usually two reclinate orbital bristles and a bare anepisternum (Mycodrosophila heterothrix McEvey & Bock has exceptional anepisternal setulation). Two Australian species lack proclinate orbitals: Liodrosophila macera Bock has only one large reclinate and Scaptodrosophila aclinata McEvey & Barker has three small reclinates; S. merdae Bock, 1984 has scaleiform reclinate orbital setae. Drosophilid species with a non-plumose arista are rare in Australia so most entomologists will, when sorting ephydroid acalyptrates, jump to that part of a generic key that separates the five largest drosophilid genera (all with plumose aristae): Scaptodrosophila (30% of the fauna), Drosophila (13%), Hirtodrosophila (11%), Leucophenga (9%) and Mycodrosophila (9%). Species of Scaptodrosophila are characterized by having one, two or all three of the following attributes: three subequal katepisternal bristles, a single vibrissa, and a proepisternal setula; Hirtodrosophila and Drosophila differ by having unequal katepisternal bristles and no proepisternal, Drosophila species have the second oral seta at least half the length of the vibrissa. Drosophilid wings are hyaline, infuscate or patterned. In species of Stegana and Eostegana wings are bent elytra-like over the abdomen when resting. The subcostal break (second incision of vein C) is sometimes deep and the distal end of the costal segment is formed into a protruding blackened lappet in Mycodrosophila s.st., Paramycodrosophila, Styloptera, Dettopsomyia and, exceptionally, in Hirtodrosophila lappetata McEvey & Bock.

Species diversity is highest in north-eastern Australia where it appears to be the product of on overflow of the extremely rich, but poorly known, New Guinean fauna. Further south in Australia a second centre of species diversity (in the McPherson Botanical Region) has a high degree of endemism: of the 108 species reported in north-eastern New South Wales and south-eastern Queensland only 42 occur also in rainforests around Cairns. About 20 species are peridomestic occurring in or near buildings, often in kitchens, especially where ferment-odours accumulate in still air around fruit, vegetable scraps, and wine or beer. In arid parts of Australia Drosophilidae are difficult to find or rare — a small assortment of species, most frequently Scaptomyza and Leucophenga species, are encountered; light-trapping is the most rewarding collecting technique in such places.

The general life-history and host preference for most species is unknown in Australia, but some important progress in this direction has been achieved by van Klinken & Walter. Many species are represented in collections by just one or a handful of specimens taken at random over large areas of Australia. Species associated with rotting fruit (and therefore easily lured to baits) and those found on deliquescing fungus are well-represented in collections because the resources are easy for collectors to locate and collect from. About 40% of the Australian drosophilid fauna - most species of Mycodrosophila and Hirtodrosophila and some species of Scaptodrosophila and Leucophenga - can be found on or near fungus, but only about 20% of species are attracted to decaying fruit; these facts highlight the inappropriateness of the name "Fruit Flies" for the entire family. Rotting, especially fermenting, fruit in kitchens, gardens and forests will lure species primarily of Drosophila, but also of Scaptodrosophila. Most species of the former and few of the latter genus are easily cultured in the lab and, as a consequence, only a small proportion of the 290 known Australian drosophilids are amenable to biological manipulation and experimentaion. But this small proportion has yielded a huge body of knowledge that informs all kinds of research in the rest of the family, indeed the rest of the animal and plant kingdoms.

It is important to note that the degree to which complexes of cryptic species have been identified among the hundreds in the Drosophila melanogaster species group is more a reflection of the depth to which they have been studied than evidence for a unique evolutionary phenomenon within the family or order. (By contrast, the extraordinary morphological diversification and speciation of hundreds of drosophilid species in Hawaii is indeed a unique phenomenon within the family and among insects generally). Were other dipterous genera amenable to such intensive analysis as Drosophila they too would probably also yield complexes of related species (e.g. Aedes: Culicidae). Taxonomic decisions within the genus Drosophila, however, continue to rest substantially on identification of differences in morphology, particularly of male terminalia.

Evolutionary studies involving Australian drosophilid species, or cosmopoltian species that occur in Australia, have been extensive (see below). Many such works have been published internationally and, to some extent, this accounts for a general underestimation of the utility of local drosophilid species as a most significant biological resource.

During the 1960s and 1970s it was popular to examine chromosome form, particularly banding patterns of polytenes. Work during those decades focussed on karyotypes and evidence of relatedness between isolated populations. Variation in polytene chromosomes and asymmetric mating preference in lab strains led, eventually, to the naming of new species, all of which were found (during entomological studies) to possess subtly divergent morphology. In the Drosophila ananassae group, however, there remains some confusion about the correlation between genotype and phenotype in northern Australia and New Guinea — it is possible that several undescribed species live alongside D. ananassae s.str. in northern Australia, New Guinea and the southwest Pacific .

Geneticists loosely apply the name 'Fruit Fly' to Drosophila species, while this is apt for some drosophilids it is a name that leads to confusion, especially in the Australian context, because of the well publicized fight against the 'true' fruit flies: Tephritidae. Unlike tephritids, the drosophilids are not known to impact negatively in any area of commerce, nor are they known to be vectors of disease in Australia; they are not known to initiate rot in unspoiled fruit but are frequently incorrectly regarded as harmful: in error, many a fruit-gardener use devices that accumulate and drown huge numbers of drosophilids as a 'control' against fruit fly (tephritids)!

Drosophila (Sophophora) flavohirta, a species that breeds in myrtaceous blossom appears to have spread from Australia to South Africa and Madagascar, where its presence diminishes honey yield from Eucalyptus. Another flower-dwelling species Scaptodrosophila hibisci, and a close congener S. aclinata, spend most of their lives within native Hibiscus flowers and have distributions extending into drier parts of Australia. The host-specific yeasts in the Hibiscus flowers and the plant-yeast-insect ecology have been very profitable areas of research in Australia by Barker and Starmer and have resulted in the discovery of an extraordinary genetic system. Another plant-yeast-insect model involves the introduced prickly pair (Opuntia spp.) and two paleaearctic species Drosophila aldrichi and D. buzzatii that occur in Australia only with the cactus and its specific yeasts (see works authored by J.S.F. Barker and Starmer). Climatic adaptation models can be based on these two species in southeastern Australia.

A very large body of evolutionary work has been done using Drosophila serrata, D. birchii and other members of the Drosophila montium species group that occur only in Australia and New Guinea (see works by Dobzhansky, Ayala, Mather, Blows, Hoffman, Partridge, Stanley, Schiffer, Jenkins etc). Genetic variation associated with latitude along Australia's east coast has become an important model for understanding the relationship between climatic patterns and insect distribution; the model organisms in these studies have been Drosophila serrata, D. melanogaster and D. simulans (see works by Parsons, Stanley, Hoffmann, Blows, Robin). General ecology and habitat associations have been studied for a range of species by (see works authored by Parsons, Bock, Grossfield, Barker, Schiffer, Mather, Angus, and McEvey). Australian drosophilid samples have played an important part in the study of bacterial symbiont/host systems by exploiting the signature of infection on the host and sequential evolution of Wolbachia and D. simulans (see works by Ballard). Drosophila bipectinata samples from Queensland have played a central role in quantitative genetic studies of fluctuating morphological asymmetry and the primary role of developmental instability in sexual selection (see numerous works by Polak with his colleagues Starmer and Taylor).



Closing Date

The closing date for entries in this section of the database was 25 September, 2008.


Limital Area: Distribution data in the Directory is by political and geographic region descriptors and serves as a guide to the distribution of a taxon. For details of a taxon's distribution, the reader should consult the cited references (if any) at genus and species levels.

Australia is defined as including Lord Howe Is., Norfolk Is., Cocos (Keeling) Ils, Christmas Is., Ashmore and Cartier Ils, Macquarie Is., Australian Antarctic Territory, Heard and McDonald Ils, and the waters associated with these land areas of Australian political responsibility. Political areas include the adjacent waters.

Terrestrial geographical terms are based on the drainage systems of continental Australia, while marine terms are self explanatory except as follows: the boundary between the coastal and oceanic zones is the 200 m contour; the Arafura Sea extends from Cape York to 124°E; and the boundary between the Tasman and Coral Seas is considered to be the latitude of Fraser Island, also regarded as the southern terminus of the Great Barrier Reef.

Distribution records, if any, outside of these areas are listed as extralimital. The distribution descriptors for each species are collated to genus level. Users are advised that extralimital distribution for some taxa may not be complete.



S.F.MCE.


References

Bock, I.R. (1982). Drosophilidae of Australia V. Remaining genera and synopsis (Insecta: Diptera). Aust. J. Zool. (Suppl. Ser.)89: 1-164

Lachance, M.A., Starmer, W.T., Rosa, C.A., Bowles, J.M., Barker, J.S.F., & janzen, D.H. (2001). Biogeography of the yeasts of ephemeral £owers and their insects. Int. J. Developmental Biol. 48(4): 1431-1443

McEvey, S.F. (1994). Results of Drosophilidae (Diptera) invertebrate fauna surveys of north-east NSW forests. North East Forests Biodiversity Report no. 3d. NSW National Parks and Wildlife Service, Sydney 64 pp.

McEvey, S.F. & Barker, J.S.F. (2001). Scaptodrosophila aclinata: a new Hibiscus flower-breeding species related to S. hibisci (Diptera: Drosophilidae). Rec. Aust. Mus. 53(2): 255-262

McEvey, S.F., Aulard, S. & Ralisoa-Randrianasolo, O. (1989). An Australian drosophilid (Diptera) on Eucalyptus and Eugenia (Myrtaceae) flowers in Madagascar. J. Aust. Entomol. Soc. 28: 53-54

Polak, M. & Starmer, W.T. (2001). The quantitative genetics of fluctuating asymmetry. Evolution 55(3): 498-511

Polak, M., & P.W. Taylor (2007). A primary role of developmental instability in sexual selection. Proc. R. Entomol. Soc. Lond. Ser. B 274: 3133-3140

Rosa, C.A., Lachance, M.A., Starmer, W.T., Barker, J.S.F., Bowles, J.M. & Schlag-Edler, B. (1999). Kodamaea nitidulidarum, Candida restingae and Kodamaea anthophila, three new related yeast species from ephemeral flowers. Int. J. syst. Bacteriol. 49(1): 309-318

Sarup, P., Sørensen, J.G., Dimitrov, D., Barker, J.S.F. & Loeschcke, V. (2006). Climatic adaptation of Drosophila buzzatii populations in southeast Australia. Heredity 96: 479-486

Schug, M.D., Smith, S.G., Tozier-Pearce, A. & McEvey, S.F. (2007). The genetic structure of Drosophila ananassae populations from Asia, Australia and the South Pacific. Genetics 175(3): 1429-1440

Stark et al. (2007). Discovery of functional elements in 12 Drosophila genomes using evolutionary signatures. Nature 450: 219-232

Tobari, Y.N. (1993). Drosophila ananassae: genetical and biological aspects. Tokyo : Japan Scientific Socieities Press/Karger pp. i-xvi + 1-289

Tribe, G.D. (1991). Drosophila flavohirta Malloch (Diptera: Drosophilidae) in eucalyptus flowers: occurrence and parasites in eastern Australia and potential for biological control on Eucalyptus grandis in South Africa. J. Aust. Entomol. Soc. 30(4): 257-262

Tribe, G.D., du Toit, A.P., van Rensburg, N.J. & Johannsmeier, M.F. (1989). The collection and release of Tetrastichus sp (Eulophidae) as a biological control agent for Drosophila flavohirta Malloch (Drosophilidae) in South Africa. J. Entomol. Soc. South. Afr. 52(1): 181-182

Van Klinken, R.D. & Walter, G.H. (2001). Larval hosts of Australian Drosophilidae (Diptera): a field survey in subtropical and tropical Australia. Aust. J. Entomol. 40(2): 163-179

Van Klinken, R.D., Walter, G.H. & Ross, M.K. (2002). Drosophilidae (Diptera) of Australia's Northern Territory: ecology and biogeography. Aust. J. Entomol. 41(3): 236-242

Wilson, A.C.C., Sunnucks,P., Bedo, D.G. & Barker, J.S.F. (2006). Microsatellites reveal male recombination and neo-sex chromosome formation in Scaptodrosophila hibisci (Drosophilidae). Genet. Res. 87: 33-43

Limital Area

Distribution data in the Directory is by political and geographic region descriptors and serves as a guide to the distribution of a taxon. For details of a taxon's distribution, the reader should consult the cited references (if any) at genus and species levels.

Australia is defined as including Lord Howe Is., Norfolk Is., Cocos (Keeling) Ils, Christmas Is., Ashmore and Cartier Ils, Macquarie Is., Australian Antarctic Territory, Heard and McDonald Ils, and the waters associated with these land areas of Australian political responsibility. Political areas include the adjacent waters.

Terrestrial geographical terms are based on the drainage systems of continental Australia, while marine terms are self explanatory except as follows: the boundary between the coastal and oceanic zones is the 200 m contour; the Arafura Sea extends from Cape York to 124°E; and the boundary between the Tasman and Coral Seas is considered to be the latitude of Fraser Island, also regarded as the southern terminus of the Great Barrier Reef.

Distribution records, if any, outside of these areas are listed as extralimital. The distribution descriptors for each species are collated to genus level. Users are advised that extralimital distribution for some taxa may not be complete.

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