D3055: (2nd Place) Aphid hosts and plants influence parasitism rates of parasitoids over multiple generations

Lysiphlebus testaceipes (Family: Braconidae) and Aphelinus nigritus (Family: Aphelinidae) parasitize aphids on sorghum in summer and wheat in winter in the US Southern Plains. Their coexistence as the two primary parasitoids in diverse landscapes is likely influenced by their ability to host switch among available plants. Host switching by aphid parasitoids is common and the relative ability to host switch and parasitize multiple species classifies parasitoids along a continuum from generalists to specialists. This study aims to describe generational fitness costs associated with host switching among plants for both A. nigritus and L. testaceipes. A replicated laboratory study was conducted to observe how A. nigritus and L. testaceipes respond to host plant and aphid changes over multiple generations. Both species were raised initially on greenbug (Schizaphis graminum) and sorghum but then switched upon emergence to various suitable host plant and aphid combinations that are commonly encountered. Percent parasitism, development time, and sex ratios were recorded, and preliminary data indicate that A. nigritus and L. testaceipes respond quite differently to aphid and plant changes among generations. Generational plasticity for both species may help to explain niche breadth and mechanisms of coexistence for these competing parasitoids in the U.S. Southern Plains.