Australian endemic Drosophila I. Tasmania and Victoria, including descriptions of two new species

The endemic Drosophila fauna of southern Australia consists principally of species of the typically Australian subgenus Scaptodrosophila. In Tasmania and Victoria (but less so further north), the inornata group of species within the subgenus predominates. With one exception, none of the southern species is found further north than the upland forest regions of the Queensland-New South Wales border, this being the most northern extension of floral elements of the temperate rain forests of the south. Species diversities increase with decreasing latitude, presumably because of the dependence of Drosophila species on the flora which itself becomes more diverse with decreasing latitude. Evidence is presented for a progressive reduction of niches available or exploited with increasing latitude. In very marginal habitats interspecific variability is low, paralleling low genetic intraspecific variability often found in such habitats. Species distributions are probably highly dependent upon density-independent factors of the climate, so that past climatic shifts would have been important in leading to distribution patterns found today of Drosophila populations in 'insular islands of vegetation' surrounded by unsuitable habitats.