PS 44-93 - Thermal mismatch in host-parasitoid interactions: novel recovery from a lethal parasitoid differs by host species under high temperatures

Background/Question/Methods

As extreme temperature events increase in frequency and severity with climate change, determining the effects of high temperatures on multitrophic species interactions and ecosystems is crucial. Here we explore a temperature-mediated disruption in parasitism of two co-occurring, congeneric insect hosts, Manduca sexta and M. quinquemaculata by the endoparasitoid wasp Cotesia congregata and its associated endogenous polydnavirus, CcBV. Adult female wasps oviposit eggs and CcBV virions into their host; the virus halts host development in the final larval instar before parasitoid larvae emerge, inevitably killing the host. Under high temperatures (non-stressful to hosts), a thermal mismatch occurs – wasp larvae/eggs do not survive, but host development remains disrupted, resulting in enormous larval host sizes and failure to wander and pupate in the final instar. However, preliminary studies suggested that some parasitized, heat-shocked hosts can recover the wandering and later stages of development. The frequency and extent of developmental recovery in either host is not presently known. In this study, we sought to quantify and compare the frequency in occurrence of developmental recovery in parasitized M. sexta and M. quinquemaculata under high temperature conditions.

Results/Conclusions

The results of this study indicate host-species specific differences in heat-induced recovery rates from an otherwise obligately lethal parasitoid. In parasitized, heat-shocked hosts surviving to 5^th instar, M. quinquemaculata recovered the prepupal wandering stage significantly more often than M. sexta (47% of M. quinquemaculata hosts wandered vs. 13% of M. sexta). This study demonstrates a temperature-dependent shift in host-parasitoid interactions, and reveals a discrepancy in permissibility to parasitism between two primary hosts under high temperature conditions. As C. congregata is the primary natural enemy of both host species in the field, the potential for recovery from parasitism represents a strong selective pressure. As such, future work includes investigations into the ecological relevance of this thermal mismatch and developmental recovery (e.g. searching for patterns of recovery from parasitism in the field, and ecological shifts in M. sexta and M. quinquemaculata co-occurrence and parasitism by C. congregata).