Host preference of three Asian larval parasitoids to closely relatedDrosophilaspecies: implications for biological control ofDrosophila 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 brasiliensisandLeptopilina japonica(Hymenoptera: Figitidae), were examined on two closely related hosts,Drosophila suzukiiandD. 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 thatA. japonicahad higher parasitism levels thanG. brasiliensisandL. 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 eitherD. suzukiiorD. 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.

Automated summary

The study found that regardless of the different degrees of host specificity among the three parasitoids, they did not show any host preference for the two closely related host species in both no choice tests and choice tests. The 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.