2018 ESA Annual Meeting (August 5 -- 10)

PS 24-148 - Interplay between competition and predation: Reproductive strategies in two parasitoid wasps

Tuesday, August 7, 2018
ESA Exhibit Hall, New Orleans Ernest N. Morial Convention Center
Rosa M. McGuire, Department of Evolution, Ecology, and Organismal Biology, University of California, Riverside, Riverside, CA, Robert M. McElderry, Department of Ecology and Evolutionary Biology, University of Tennessee, Knoxville, TN and Priyanga Amarasekare, Department of Ecology and Evolutionary Biology, University of California, Los Angeles, Los Angeles, CA
Background/Question/Methods

Competitive and predator-prey interactions constitute the fundamental building blocks of communities. We know a great deal about how competition and predation individually affect community dynamics. But, we know very little about how the interplay between competition and predation influences such dynamics. Species engaging in intraguild predation (i.e., competitors that prey on or parasitize one another) provide an excellent model system to investigate the interaction between competition and predation. Here we investigate the reproductive strategies of two parasitoids of the harlequin bug (Ooencyrtus johnsonii and Trissolcus murgantiae), which compete for hosts at the adult stage and engage in intraguild predation at the larval stage. Adult T. murgantiae engages in aggressive displays and physical combat to monopolize hosts; adult O. johnsonii do not engage in such interactions. However, adult O. johnsonii can lay multiple eggs within a single host egg and can multiparasitize host eggs previously parasitized by T. murgantiae; adult T. murgantiae do not engage in multiparasitism. We quantified the frequency of aggressive interactions by T. murgantiae, and their outcomes, using video analyses. We quantified the frequency of multiparasitism in O. johnsonii by testing their preference for previously parasitized eggs by conspecifics and T. murgantiae.

Results/Conclusions

In our preliminary data we found a marginally significant preference by O. johnsonii for uninfected host eggs. In ongoing experiments, we also measure the effect of larval age on O. johnsonii's multiparasitism success. Preliminary results suggest that O. johnsonii larvae can successfully outcompete, via intraguild parasitism, T. murgantiae larvae up to nine days of age. Our ongoing experiments have the potential to provide insights into how differences in reproductive strategies associated with competition and intraguild predation can allow parasitoid coexistence in nature. Through the quantification of the relative strengths of exploitative competition and intraguild parasitism, our experiments also inform the biological control practices that use multiple natural enemies to control agricultural pests.