Effects of xanthotoxin on parasitoid-host systems in generalist herbivores Trichoplusia ni and Chrysodeixis includens parasitized by Copidosoma floridanum.

Copidosoma floridanum is a species of parasitoid wasp that is known to affect species of Lepidopterans. This parasitoid is expected to react poorly to plant defense mechanisms affecting its hosts, in this case the two generalist herbivores Chrysodeixis includens and Trichoplusia ni, in the subfamily Plusiinae. The defensive compound xanthotoxin is produced by plants in the family Apiaceae. Previous research has shown the chemical to negatively affect both the generalist host T. ni and its parasitoid wasp. In this study, both parasitized and unparasitized T. ni and C. includens are reared on four increasing concentrations of dietary xanthotoxin. The two hosts are evaluated for development time and quality of life, which is measured in pupal mass and survival rate. As xanthotoxin concentrations increased, survival rate and quality of life were expected to decrease, and development time was expected to increase. Statistical analysis for this study did reveal an increase in development time as well as pupal mass with increased treatment. The increased treatment did not, however, affect parasitoid brood size. Due to the prevalence of specialist herbivores, generalist herbivores have been researched less. By comparing how two closely-related parasitoid-host systems react to one defensive chemical, we are able to understand the ways that closely related generalist species develop differing metabolic responses to harmful plant chemical defenses. This experimental contribution will help improve our understanding of multitrophic interactions between parasitoids and their generalist hosts and how they evolve.