Host preference of three Asian larval parasitoids to closely related Drosophila species: implications for biological control of Drosophila suzukii

Insect parasitoids can attack phylogenetically related hosts that share similar physiological properties and defense mechanisms and, more importantly, overlapping ecological niches. Here, host preferences of three parasitoids, Asobara japonica (Hymenoptera: Braconidae), Ganaspis brasiliensis and Leptopilina japonica (Hymenoptera: Figitidae), were examined on two closely related hosts, Drosophila suzukii and D. melanogaster (Diptera: Drosophilidae). Each parasitoid’s rate of successful parasitism (or offspring survival) on these hosts was first compared in no choice tests. Results showed that A. japonica had higher parasitism levels than G. brasiliensis and L. japonica, and that offspring survival for all parasitoids was similar on both host species. Host preferences in choice tests were then compared, with each parasitoid presented with the two host species at different proportions of host abundance. None of the parasitoids showed host preference or host switching, even though these parasitoids have different degrees of host specificity, from more generalized (A. japonica) to more specialized (G. brasiliensis). Further examination of parasitoid olfactory responses showed all three parasitoid species were attracted to volatiles from fruit infested by either host species and showed no preference to either D. suzukii or D. melanogaster. Results suggest that the hosts’ phylogenetical similarity and a lack of any obvious fitness costs for offspring survival may reduce host preference by these larval parasitoids.