Abstract
Plasticity has evolved across the animal kingdom, providing energetic tradeoffs to optimize behavior and reproduction. Brain plasticity provides advantages to process information from changing cues and cognitive demands, and reproductive plasticity is influenced by energetic costs and benefits of reproduction. Therefore, I hypothesize that investment in brain tissue and reproduction will be influenced by selective pressures from different ecological and social contexts. I take advantage of Polistes dominula, a wasp species with three distinct phenotypes to test this differing investment hypothesis. First, females are social with a flexible caste system, behavior and reproduction. Second, males spend most of their life in leks outside their nest. The third phenotype consists of female workers who are parasitized, gregarious, and castrated. I quantified volume and shape of brain regions that receive and process olfactory and visual stimuli, and measured corpora allata volume to analyze reproductive plasticity in all three phenotypes. Between the sexes, I found that males have larger brain regions that receive visual information, while females have larger brain regions that receive and process olfactory information. In addition, hyperparasitized females have smaller visual processing regions compared to unparasitized females. My results suggest that sensory and processing needs differ among the three phenotypes. Finally, differences in corpora allata volume highlight differences between sexes, and importantly, that manipulation by the parasite has a potential pathway through the corpora allata of infected females. Together, these results provide novel insights into how neural and reproductive plasticity are influenced by development, sex, and manipulation by an endoparasitoid.