Shane McEvey has a research interest in the taxonomy, biogeography and evolutionary biology of Drosophilidae (Diptera) in Australia, New Guinea, southern Africa, Madagascar, and across the islands of the Indian Ocean and South Pacific. He studied entomology in Melbourne and evolutionary biology in Johannesburg. He has worked as a drosophilid taxonomist for the CNRS in France (1985-1990) and the Australian Museum in Sydney since 1990. In 1997 he became the Editor of Records of the Australian Museum. He is a collaborator with geneticists in the study of Drosophila evolution in natural populations and with other science publishers and taxonomists in the digitizing of the taxonomic literature.
Abstract: Examination of the holotype and a paratype of Drosophila setifemur Malloch, 1924 in the Australian Museum has resulted in the discovery that it is not a synonym of D. sulfurigaster as had previously been assumed. Instead, D. setifemur is a senior synonym of the widespread eastern Australian species D. dispar Mather, 1955. The so-called Drosophila dispar species group is renamed the Drosophila setifemur species group and Drosophila unguicula is removed from it. An illustrated key to Australian drosophilids with spinescent fore-femora is provided.
Abstract: Prezygotic mating isolation has been a major interest of evolutionary biologists during the past several decades because it is likely to represent one of the first stages in the transition from populations to species. Mate discrimination is one of the most commonly measured forms of prezygotic isolation and appears to be relatively common among closely related species. In some cases, it has been used as a measure to distinguish populations from subspecies, races, and sister species, yet the influences of various evolutionary mechanisms that may generate mate discrimination are largely unknown. In this study, we measured the level and pattern of mate discrimination among 18 populations of a cosmopolitan drosophilid species, Drosophila ananassae, from throughout its geographical range and its sister species, Drosophila pallidosa, which has a restricted geographical distribution in the South Pacific Islands. In addition, we measured genetic differentiation between all 18 populations using mitochondrial DNA polymorphism data. Mate discrimination varies considerably throughout the species range, being higher among populations outside the ancestral Indonesian range, and highest in the South Pacific. Our results suggest that colonization and genetic differentiation may have an influence on the evolutionary origin of mate discrimination. Our phylogeographical approach clarifies the ancestral relationships of several populations from the South Pacific that show particularly strong mate discrimination and suggests that they may be in the early stages of speciation. Furthermore, both the genetic and behavioral results cast doubt on the status of D. pallidosa as a good species.
Abstract: Information about genetic structure and historical demography of natural populations is central to understanding how natural selection changes genomes. Drosophila ananassae is a widespread species occurring in geographically isolated or partially isolated populations and provides a unique opportunity to investigate population structure and molecular variation. We assayed microsatellite repeat-length variation among 13 populations of D. ananassae to assess the level of structure among the populations and to make inferences about their ancestry and historic biogeography. High levels of genetic structure are apparent among all populations, particularly in Australasia and the South Pacific, and patterns are consistent with the hypothesis that the ancestral populations are from Southeast Asia. Analysis of population structure and use of F-statistics and Bayesian analysis suggest that the range expansion of the species into the Pacific is complex, with multiple colonization events evident in some populations represented by lineages that show no evidence of recent admixture. The demographic patterns show isolation by distance among populations and population expansion within all populations. A morphologically distinct sister species, D. pallidosa, collected in Malololelei, Samoa, appears to be more closely related to some of the D. ananassae populations than many of the D. ananassae populations are to one another. The patterns of genotypic diversity suggest that many of the individuals that we sampled may be morphologically indistinguishable nascent species.
Abstract: Physiological, ecological and evolutionary studies of Scaptodrosophila hibisci have led to recognition of a second species in the Northern Territory (Australia) which is described here as Scaptodrosophila aclinata n.sp. The new species is readily distinguishable by reference to the first orbital: it is large and proclinate in S. hibisci and small and reclinate in S. aclinata. Scaptodrosophila hibisci has been collected from the flowers of five Hibiscus species in eastern Australia and S. aclinata uses eleven Hibiscus species in the Northern Territory. Only H. meraukensis is a host for both, and there is no evidence of narrow host-specialization. The distributions are apparently disjunct. The two species can be reared in the laboratory on cultured plants. Hybridization studies showed the two species to be partially interfertile; S. aclinata has delayed sexual maturation and extended copulation latency when compared to S. hibisci. This species pair is already the subject of various eco-physiological and reproductive-biological studies because of so many useful experimental attributes: they are interfertile and can be laboratory-cultured, their hosts and reproductive biology are known, they are abundant and easy to find, and research is underpinned by extensive genetic information already available for Drosophila.
Abstract: The relationship between allelic frequencies at the Adh locus and latitude of origin was studied using selected published data from various parts of the world and original observations. An overall increase of Adh-F with increasing latitude was observed but the relationship is not linear. Tropical populations are generally similar, having a low frequency of the F allele (average 15 per cent) and a smooth increase with latitude (one per cent for one degree). Between 30 and 42 degrees latitude, populations living in a Mediterranean climate in various parts of the world (Mediterranean countries, Australia's east coast and North America's west coast) are also similar, with a much higher average frequency of F (70 per cent), a steeper slope (two per cent) and a broader range of variability for a given latitude. In a restricted area (near Cordoba in southern Spain) numerous wild collected samples also showed a large variability, sometimes over a very short distance. Allelic frequencies in Mediterranean countries are thus quite unstable and it is proposed that this phenomenon be called a "Mediterranean instability". Further north, numerous samples from France were characterized by an even higher frequency of F (95 per cent) and a greater homogeneity over a broad geographic area. These observations are discussed and the need for more field studies is emphasized.
