An analysis of heterosis and outbreeding depression among lab-reared populations of the parasitoid Diachasmimorpha tryoni (Cameron) (Hymenoptera: Braconidae); potential implications for augmentative releases

Abstract

Augmentative biological control is a process in which a biocontrol agent is mass-reared and released to either augment the existing population present in the field or inundate the target pest population. Although research into the utility of augmentative biocontrol has been conducted for ∼50years, little is known about the effect of inundative releases on the progeny of the released population and the wild population. We used the arrhenotokous haplo-diploid tephritid parasitoid Diachasmimorpha tryoni (Cameron) (Hymenoptera: Braconidae) to model a theoretical augmentative release interaction. By employing a combination of molecular techniques and a fitness proxy, our results were capable of documenting the hybridization of a “released” and “wild” population (as modeled in vitro). These analyses revealed significant hybridization interactions between two moderately differentiated populations (Fst/Rhost=0.1352/0.0641), as would be the case during an augmentative release. Our analysis also revealed an outcrossing asymmetry of hybrid progeny relating to parental population origin. This interaction has the potential to either hinder or facilitate augmentative control and may prove useful to future augmentative releases.