Electronic Thesis and Dissertation Repository


Doctor of Philosophy




McNeil, Jeremy N

2nd Supervisor

Gariepy, Tara D



The intra- and inter-trophic interactions in ecosystems can be disrupted by invasive species, with lasting effects on population dynamics of native organisms. An invasive species may be attractive as a prey or host to native species, but if unsuitable for consumption or for development of the natural enemy’s progeny, it constitutes an ‘evolutionary trap’. A possibility of such a trap for native egg parasitoids (Hymenoptera: Scelionidae) exists with the introduction of the exotic brown marmorated stink bug, Halyomorpha halys (Hemiptera: Pentatomidae). The objective of this thesis is to enhance the understanding of Pentatomidae-Scelionidae host-parasitoid interactions from a behavioural ecology perspective, focusing on factors influencing successful host use by egg parasitoids associated with stink bugs. Behavioural, molecular, and imaging methodologies were employed to elucidate trophic and competitive interactions of native egg parasitoids with invasive host, H. halys, and with an interspecific competitor, the exotic Trissolcus japonicus (Hymenoptera: Scelionidae) egg parasitoid. First, sentinel egg masses were exposed under natural conditions, followed by parasitism quantification, using both traditional (parasitoid emergence) and molecular analysis. Second, the outcomes of competitive interactions between exotic and native egg parasitoids using H. halys as host were characterized and the possibility of their coexistence assessed. Third, an L9 orthogonal array (OA) design was used to rank the influence of host egg mass parameters on parasitoid behaviour and development. Finally, the temporal pattern of parasitoid development in H. halys was examined using a DNA-based approach (PCR) and visualized by X-ray micro-computed tomography (micro-CT).

The key finding of this thesis is that the lack of success in H. halys eggs is linked to native parasitoids’ inability to develop in this host (not the rejection of the host). This failure occurs early in the parasitoid development, confirming the evolutionary trap potential of H. halys. The maladaptive decision to oviposit in an unsuitable host is caused by the mismatch between cues females use for host recognition and acceptance, and the expected normal development of the progeny. For some native parasitoids, the impact of the evolutionary trap can be reduced via facultative hyperparasitism of exotic parasitoids; for others, the co-existence is possible due to counterbalance competition.