Climatic and biotic influences on the distributions of Calliphora augur and Calliphora dubia (Diptera: Calliphoridae)

Calliphora augur (Fabricius) and Calliphora dubia (Macquart) are two widespread and endemic Australian blowflies of applied importance. In order to better understand the biology of these species, this study used historical, field and laboratory data to determine and interpret their distributions. Locality records from insect collections and the literature were used to determine the known distributions of each species. The resultant maps were partially verified with field trapping data for each species. Calliphora augur was found to dominate in the east of Australia, while C. dubia dominates in the west. Comparative laboratory and field experiments were also used to derive parameters defining the distributions of these two closely related species, particularly in relation to temperature and moisture. Calliphora dubia had a greater tolerance for dry stress and high temperatures than C. augur, although maggots of both species displayed similar developmental temperature preferences. No difference was seen between species in the impact of low temperatures on the development of maggots through to the pupal stage. The greater ability of C. dubia to tolerate adverse environmental conditions is most likely linked to the shared evolutionary history of both species, in which increased aridity in central Australia is proposed to have triggered speciation by separating ancestral populations: C. dubia evolved in the hot, dry conditions in the west of Australia, while C. augur evolved in the cooler, moist environment of the east. Improved understanding of the influences on the distributions of these common Australian blowflies will assist in the further study of their application to agriculture and forensic science.