Species-level identification of the blowfly Chrysomya megacephala and other Diptera in China by DNA barcoding

The blowfly Chrysomya megacephala, or oriental latrine fly, is the most common human-associated fly of the oriental and Australasian regions. Chrysomya megacephala is of particular interest for its use in forensic entomology and because it is a disease vector. The larvae are economically important as feed for livestock and in traditional Chinese medicine. Identification of adults is straightforward, but larvae and fragments of adults are difficult to identify. We collected C. megacephala, its allies Chrysomya pinguis and Protophormia terraenovae, as well as flies from 11 other species from 52 locations around China, then sequenced 658 base pairs of the COI barcode region from 645 flies of all 14 species, including 208 C. megacephala, as the basis of a COI barcode library for flies in China. While C. megacephala and its closest relative C. pinguis are closely related (mean K2P divergence of 0.022), these species are completely non-overlapping in their barcode divergences, thus demonstrating the utility of the COI barcode region for the identification of C. megacephala. We combined the 208 C. megacephala sequences from China with 98 others from public databases and show that worldwide COI barcode diversity is low, with 70% of all individuals belonging to one of three haplotypes that differ by one or two substitutions from each other, reflecting recent anthropogenic dispersal from its native range in Eurasia.