Parasitoid-host associations of the genus coccophagus (Hymenoptera: Aphelinidae) in China

Host relationships among many Aphelinidae are complex due to their heteronomous reproductive behaviour, where males have different host relationships from females. Heteronomous parasitoids present a fascinating problem in host selection and sex ratio decision making. Accurate identification of insect parasitoids is a prerequisite in the determination of parasitoid-host relationships. With the goal of disentangling the parasitoid-host associations in the genus Coccophagus, we compared the performances of the COI barcode and of the 28S-D2 rRNA region for identification and delimitation of 17 morphospecies of Coccophagus parasitoid wasps collected during a 9-year rearing programme of scale insects in China. Molecular data were analysed by two different methods of species delimitation, the automatic barcode gap discovery and the general mixed yule coalescent. Both methods were effective in discriminating all previously recognized morphospecies. The congruence of morphospecies delimitation with that obtained by DNA barcode and nuclear gene data greatly enhanced our ability to unravel the parasitoid-host associations of genus Coccophagus. Most Coccophagus species (11 out of 17) can use host species belonging to different genera, with different levels of host specificity, particularly in host selection to produce female offspring. Sex-related differences in host relationships have also been detected and discussed.