Location: Beneficial Insects Introduction ResearchTitle: Is parasitoid acceptance of different host species dynamic? Author
Submitted to: Functional Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/19/2013
Publication Date: 5/21/2013
Citation: Hopper, K.R., Prager, S., Heimpel, G.E. 2013. Is parasitoid acceptance of different host species dynamic?. Functional Ecology. 10.1111/1365-2435.12107. Interpretive Summary: Testing specificity of candidates for biological control introductions is crucial for the safety and approval of introductions. It is possible that the conditions of testing may influence the measurement of specificity. In particular, the internal physiological state and previous experience of parasitic wasps can change their egg laying behavior among categories of host individuals within species that differ in suitability for wasp progeny (small versus large, previously parasitized or not). However, noone has tested whether the internal physiological state and previous experience of parasitic wasps can change their egg laying behavior among host species that differ in quality. Here, we report the first results on whether acceptance of host species that vary in quality is also dynamic. Stresses (starvation and age) and differences in experience did not affect acceptance of low quality host species by one parasitoid species, and had a weak effect on another species. This result shows that host specificity is unlikely to change with internal and external conditions, at least for parasitic wasps with narrow host ranges, which is good news for testing host specificity of candidates to be used in biological control.
Technical Abstract: Choice of host individuals by parasitoids is dynamic, varying with physiological state and experience. In particular, female parasitoids with high egg loads and low life expectancy are more willing to accept low quality hosts than females with low egg loads and high life expectancy. However, studies of dynamic acceptance behavior in parasitoids have only considered high versus low quality hosts within the same host species. Here, we report the first results on whether acceptance of host species that vary in quality is also dynamic, using aphid parasitoids in the genus Aphelinus (Hymenoptera: Aphelinidae). Stresses (starvation and age) and experience that should increase the perception of time limitation did not affect acceptance of low quality host species by one Aphelinus species, and had a weak effect on another species. Oviposition in a high quality host species increased with egg load (as expected), but did not vary with egg load for females exposed to low quality host species. This is an unexpected pattern since the proportional acceptance of low quality hosts decreases with increasing egg load. Three hypotheses may explain the lack of a shift to less specificity in these parasitoids: (1) frequent transient egg limitation, (2) higher fitness from egg resorption than oviposition, and (3) neural contraints on host recognition. Rejection of hosts both for host feeding and oviposition, and variation among females in acceptance of low quality host species suggests that the latter hypothesis may hold.