Intra and interspecific competition between Diachasmimorpha longicaudata (Hymenoptera Braconidae) and Aganaspis pelleranoi (Hymenoptera Figitidae)

Abstract

Braconidae and Figitidae parasitoids are important agents of pest population regulation in natural and agricultural systems, with species used in applicate biological control programs of fruit flies (Diptera Tephritidae). However, many aspects of the interactions of parasitoids with their heterospecific and conspecific are poorly understood. Thus, the interspecific competition between the par- asitoids Diachasmimorpha longicaudata (Ashmead) (DL) (Hymenoptera Braconidae) and Aganaspis pelleranoi (Brethes) (AP) (Hymenoptera Figitidae), was studied using Anastrepha fraterculus (Wiedemann) (Diptera Tephritidae) as host. Host larvae were offered to only one parasitoid on a single occasion or on two occasions, or even to two parasitoid species, alternating the offering sequence. Thus, six exposure regimes were completed: AP (host exposed for 4 hours); DL (host exposed for 40 minutes); AP-AP (host exposed to AP for 4 hours and then to a conspecific for an additional further 4 hours); DL-DL (host exposed to DL for 40 minutes and then to a conspecific for an additional 40 minutes); AP-DL (host exposed to AP for 4 hours and then to DL for 40 minutes); and DL-AP (host exposed to DL for 40 minutes and then exposed to AP for 4 hours). The mean number of parasitized pupae, emerged parasitoids, oviposition scars per host (larvae) and sex ratio of parasitoids were compared between the different exposure regimes. The mean of parasitized pupae and emerged parasitoids was higher in the DL-DL and DL-AP treatments. The mean number of oviposition scars per host was correlated positively with the mean number of parasitoid offspring and the emerged females in treatments AP, DL, AP-AP, DL-DL for both species, and DL-AP only to D. longicaudata. When the hosts were exposed only once to the parasitoids, the sex ratio was male biased (AP and DL treatments); but when exposed twice, the treatments spawned offspring female biased, except for D. longicaudata at AP-DL treatment. Irrespective of the parasitism order, D. longicaudata suppress the emergence of A. pelleranoi.