Nutritional status influences behavior, physiology, and brain gene expression in primitively eusocial Polistes metricus paper wasps

Nutrition is known to influence the division of labor in advanced eusocial insects such as the honey bee, but it is not known whether differences in nutrition can influence the social behavior of primitively eusocial insects such as Polistes metricus paper wasp. This is an interesting consideration because if the related behaviors displayed by these two independently evolved social insects are mediated by similar pathways, it may give more insight into the evolution of eusociality. We tested the effect of nutrition on worker division of labor in primitively eusocial insects at three different levels: behavior, physiology, and brain gene expression. In order to understand the effects of nutrition, I manipulated the amount of nutrients received by Polistes metricus wasp colonies in the laboratory. The starved group received less prey and sugar during a limited time frame while the fed group received a normal amount of prey and unlimited sugar source. Starvation was found to have large effects on behavior, causing a significantly elevated number of foraging trips per colony after the treatment began. The mean number of foraging trips per day for individual starved wasps was also significantly higher than for fed wasps. Starvation also caused a slightly significant increase in the proportion of foragers in a colony. At the physiological level, individuals from starved colonies had significantly lower abdominal lipid stores than individuals from fed colonies. In addition, there was a significant negative correlation between abdominal lipid and foraging activity for individual wasps in starved, but not fed colonies, showing that individuals with greatly reduced lipid stores foraged at a much higher level. In order to infer the degree of conservation of gene expression influencing worker division of labor, I analyzed brain expression for 24 genes known to be associated with division of labor in honey bees. Some genes showed expression trends similar to that of honey bees while other genes showed different expression trends. The molecular data provide further support for the idea of a ???genetic toolkit??? for eusocial behavior because novel regulation of these conserved genes contributes to new forms of related behaviors. The results of this study demonstrate that nutrition has an important role in Polistes metricus paper wasps at three different levels: behavior, physiology, and brain gene expression