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

Abstract

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. Keywords Biological control • Host range • Host selection • Invasive species • Spotted-wing drosophila Key message • The preference for two hosts (Drosophila suzukii and D. melanogaster) was assessed for three parasitoids (Asobara japonica, Ganaspis brasiliensis and Leptopilina japonica) • The parasitoids did not display a preference between these closely related hosts, nor host switching • All parasitoid species were attracted to volatiles from fruit infested by either host and none of the parasitoids showed a preference to different hosts • The results provide new insights for classical biological control and potential apparent competition between closely related hosts

Potential host ranges of three Asian larval parasitoids of Drosophila suzukii

“…Results are presented as mean ± SE. As described in Biondi et al (2021) for assessing the impact of fly larvae in fruit versus artificial diet, the impact of host species on the development of parasitoid offspring was compared using "Successful Rate of Parasitism" (SP) to determine the probability that a parasitized host would give rise to an adult wasp. SP is calculated as ep/ (ef − efp), where ep = number of emerged parasitoids, ef = the average number of emerged flies in the absence of parasitoids (control), and efp = number of emerged flies in the presence of parasitoids.…”

“…The two figitid species were kept with males from adult emergence and were assumed to be mated, whereas virgin female A. japonica were used as this species has a strongly female-biased sex ratio and the tested strain was primarily parthenogenetic (Daane et al 2016). Details on some aspects of the biology of these parasitoids, reared on D. suzukii, have been presented previously (Biondi et al 2021;Girod et al 2018a, c;Wang et al 2018Wang et al , 2019aWang et al , 2021.…”

“…Basic biological traits and potential competitive interactions of these three parasitoids have been evaluated in quarantine facilities in Switzerland (Girod et al 2018b, c) and California (Biondi et al 2017(Biondi et al , 2021Wang et al 2018Wang et al , 2019aWang et al , 2020Wang et al , 2021. Non-target impacts were first reported on five European drosophilid species for populations of G. brasiliensis from Kunming, China and Tokyo, Japan; populations of L. japonica from Kunming and Beijing, China; and a population of A. japonica from Tokyo, Japan (Girod et al 2018b).…”

Effect of Drosophila suzukii on Blueberry VOCs: Chemical Cues for a Pupal Parasitoid, Trichopria anastrephae

“…In support of this, the generalist parasitoid T. drosophilae showed no differential preference for D. melanogaster or D. suzukii pupae (Wang et al 2016). Similarly, a recent study by Biondi et al (2020) showed that the larval parasitoids, Asobara japonica Belokobylskij (Hymenoptera: Braconidae), Leptopilina japonica Novković & Kimura and Ganaspis brasiliensis (Ihering) (Hymenoptera: Figitidae), respond to fruit volatile cues associated with the presence of either D. suzukii or D. melanogaster (Biondi et al 2020).…”

Detection of the spotted wing drosophila, Drosophila suzukii, in continental sub-Saharan Africa

“…Recent studies increase the general concern about insecticide resistance in D. suzukii advocating the application of sustainable pest control methods (Gress and Zalom 2019). Biological control is a promising route to reduce D. suzukii infestation using natural enemies and insect pathogens (Becher et al 2018;Biondi et al 2020;Daane et al 2016;Gabarra et al 2015;Lee et al 2019;Wolf et al 2020). Findings on the specificity of parasitoids with respect to Drosophila host species, different fruit species as well as fruit ripeness give grounds for hope toward the development of biological control (Girod et al 2018;Wolf et al 2020;Biondi et al 2020;Seehausen et al 2020).…”