Host immunity, non-reproductive effects and kleptoparasitism from novel interactions: A case study with the fruit fly parasitoid Psyttalia fletcheri (Hymenoptera: Braconidae)

Abstract

Interactions between a parasitoid and its host may result in successful parasitism, unsuccessful parasitism due to host immunity, or parasitoid-induced host mortality especially in a novel interaction (non-reproductive effects). Previous parasitism by a suitable parasitoid may suppress a host’s immune response, allowing a non-suitable parasitoid to develop from the host (kleptoparasitism). This study illustrated these interactions and outcomes between the solitary larval endoparasitoid Psyttalia fletcheri (Hymenoptera: Braconidae) and its co-evolved (Zeugodacus cucurbitae) and novel (Bactrocera dorsalis, B. latifrons, and Ceratitis capitata) (all Diptera: Tephritidae) hosts in the aftermath of biological control introductions against these invasive pests in Hawaii. We demonstrated that the parasitoid could accept all four hosts for oviposition. As a reproductive host, however, B. dorsalis was not suitable, as the parasitoid’s eggs and first instars were encapsulated and only 0.4% of the parasitoid’s progeny developed to adults; B. latifrons was moderately suitable, with a 15.3% emergence rate; C. capitata was as suitable as Z. cucurbitae. After B. dorsalis was parasitized first by its most effective parasitoid, Diachasmimorpha longicaudata (Hymenoptera: Braconidae), 1.9% of P. fletcheri offspring developed to adults in B. dorsalis. Similarly, Z. cucurbitae was not suitable for D. longicaudata, but after Z. cucurbitae was first parasitized by P. fletcheri, followed by D. longicaudata, 1.4% of the latter species developed to adults. Parasitization by P. fletcheri induced high host mortalities in unsuitable hosts. Extensive surveys did not recover any P. fletcheri from 22,359 puparia of B. dorsalis, B. latifrons, and C. capitata collected from various host fruits on the Hawaiian Islands, and this parasitoid emerged only from Z. cucurbitae. We discuss the implications of these results for host specificity assessment in biological control of tephritid fruit flies.