Submitted to: Entomologia Experimentalis et Applicata
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/8/2004
Publication Date: 11/20/2004
Citation: Ode, P.J., Hopper, K.R., Coll, M. 2004. Oviposition vs. offspring fitness in Aphidius colemani parasitizing different aphid species. Entomologia Experimentalis et Applicata. Entomologia Experimentalis et Applicata. 115(2): 303-310. Interpretive Summary: Parasitic wasps which use a broad range of host species have an advantage over those with narrow host ranges because they may switch host species when one host becomes difficult to find. Yet, many parasitic wasps attack only a handful of species. Why aren't host ranges of such species broader? The answer to this question is important not only for the theory of host- parasite interactions but also for practial biological control. Many pest populations are ephemeral, and parasitic wasps that can switch to alternative host species are better able to persist in the environment without the need of potentially costly augmentative releases. On the other hand, parasites with overly broad host ranges may affect non-target species in unwanted ways. We used a series of experiments to examine the factors affecting host use in a parasitic wasp, Aphidius colemani, that attacks pests like the cotton aphid and oat/bird-cherry aphid, which are major agricultural pests. We found that this wasp chooses to parasitize host species in which its progeny have the greatest chance of surviving, which explains differences in the rate at which it attacks the cotton aphid versus the oat/bird-cherry aphid. These results provide better understanding of the conditions under which this parasitoid will be an effective biological control agent.
Technical Abstract: We examined use of four aphid species by a population of a polyphagous aphid parasitoid, Aphidius colemani (Hymenoptera: Braconidae). We measured the effects of the host species in which offspring developed (exposure host) and in which parents developed (development host) on host acceptance and suitability. The number of mummies and adult offspring varied among exposure hosts. Fewer adult offspring emerged from Rhopalosiphum padi tha from three other species of aphids (Myzus persicae, Aphis gossypii, and Schizaphis graminum). Development host also affected number of mummies and adult offspring, probably through effects on maternal body size. Sex ratios of adult progeny were more male biased from R. padi than from the other three aphid species. Adult female A. colemani may have chosen to lay male progeny in R. padi, because this species was a poor quality host. Ovipositing A. colemani encountered R. padi at a lower rate than A. gossypii, and A. colemani spent more time handling R. padi than A. gossypii. Furthermore, offspring of A. colemani survived less well in R. padi compared to A. gossypii. These findings suggest that oviposition preference and offspring performance are correlated in A. colemani.