The evolution of ectoparasitism in the genus Lucilia (Diptera:Calliphoridae).

To consider the evolutionary origin of the ectoparasitic habit in the blowfly genus Lucilia (Diptera:Calliphoridae), phylogenetic analyses of mitochondrial DNA sequence data were performed for 10 species, including all the common Lucilia agents of myiasis, collected from Africa, Australasia, North America and Europe. Complementary genetic distance and parsimony analyses are used to consider inter and intraspecific relationships within the genus with reference to previous morphological work. The results support the hypothesis of independent multiple evolution of the ectoparasitic habit in Lucilia sericata, Lucilia cuprina and the Lucilia caesar/Lucilia illustris group and suggest that it has coevolved in relatively recent history along with the domestication and husbandry of sheep. The geographic differences in pathogenic importance of various species of Lucilia also suggest that there is a strong climatic influence determining which species has dominated. Lucilia cuprina has become the predominant pathogenic species in sub-tropical and warm temperate habitats (e.g., Australia and South Africa), L. sericata in cool temperate habitats (e.g., Europe and New Zealand) and L. caesar and L. illustris become more common in sheep myiasis in more northerly Palaearctic regions.