SG: Understanding the genetic and behavioral basis of novel social phenotypes in damaging invasive wasps

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Invasive species can become major urban pests, damage agriculture, and devastate native species in invaded areas. Despite such widespread harm, many questions remain about what characteristics of invaders allow them to spread. Among invasive species, social insects are more harmful due to their large colony sizes and cooperative behaviors. One trait, the ability to form groups containing multiple queens, is shared by several of the most devastating invasive social insects, including Argentine ants, fire ants, and yellowjacket wasps. Combining an experiment, behavioral observations, and genetic analyses, our research asks why and how invasive yellowjacket wasps form multi-queen colonies. This project will compare native populations, where most colonies have a single queen and persist for one year, to invasive populations, where colonies contain multiple queens, grow to very large sizes, and may persist for several years. This system provides an ideal opportunity to study multi-queen societies and to identify strengths and weaknesses of this strategy. This research will also inform efforts to control invasive wasps. The research supports educational opportunities for students and will benefit society by providing basic information on the factors influencing invasiveness of non-native species.Although societies composed of non-relatives occur in many organisms, the drivers of the transition from simple family-based social groups to more complex social organization remain enigmatic. Yellowjackets (Vespula spp.) present a fascinating model system because the transition to multi-queen, perennial colonies has occurred recently and convergently in different invasive populations. This incipient phenotype offers a window into the dynamic processes underlying early stages of a major evolutionary transition. Using a three-pronged approach, this project will shed new light on the requeening process. Requeening distinguishes the multi-queen, perennial colonies found in the invasive range from the single-queen, annual colonies that occur in most of the native range. First, in field trials, mated queens will be experimentally introduced to colony entrances to directly test the behavioral response and gene expression profiles of queens and workers from both native and invasive populations. If workers in multi-queen colonies are more likely to accept new queens, they should display decreased aggression toward introduced queens compared to workers from single-queen colonies. In parallel, genes known to mediate aggression in other insects should be differentially expressed in the brains of workers and queens during queen introduction in the single- versus multi-queen colonies. Additional regulatory differences between these two social contexts will be identified. Second, the genetic structure of colonies will be surveyed successively in the invasive habitat to determine when in the colony life cycle requeening occurs, relatedness among co-occurring queens, and to estimate the longevity of founding and joining queens. Finally, reproductive partitioning in multi-queen, polygynous colonies will be assessed by genotyping hundreds of age-matched brood. Understanding the interactions between colony queen number, queen longevity and reproductive partitioning will provide novel insights into the selective forces that mediate this major evolutionary transition and, in this system, a harmful invasive phenotype.