Collaborative Research: Scents of Self: How Trade-offs Shape Self/Non-self Recognition Cues in a Supercolonial Insect

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Insects live in a world of chemical signals. Chemicals are used as defensive weapons, to signal danger, to mark resources for later foraging or for avoidance, and to identify mates of the correct species and assess their quality. The social insects take this chemically-oriented lifestyle to an extreme. The sophisticated division of labor in social insect colonies requires exquisite regulation of individual behaviors, and chemical pheromones are crucial for organizing work within the colony. Despite these important and diverse roles, we have only a rudimentary understanding of how pheromones originate and evolve. In this project genetic manipulations, pheromone analyses, and behavioral tests will be combined to clarify how various forces of natural selection shape chemical communication in a social insect. This research will be performed using the invasive Argentine ant (Linepithema humile) as a model system. This ant, a globally widespread invader, is considered one of the 100 worst invasive species in the world, and is a significant agricultural and structural pest. The research is likely to reveal pheromonal and behavioral processes that can be targeted in the development of new control techniques, thus contributing to greater ecological resilience, enhanced food quality and security, and reduced degradation of soil and water by conventional insecticides. Self/non-self recognition systems have played a central role in many of the major evolutionary transitions. Because components of these recognition systems are often co-opted from existing systems, they can experience conflicting forms of selection after acquiring their new functions. The societies of eusocial insects are an ideal system in which to study the evolutionary trade-offs associated with the evolution of self/non-self recognition systems. In many eusocial insects, cuticular hydrocarbons (CHCs) are used to distinguish colony mates (self) from non-colony members (non-self). However, CHCs have also retained their original function as barriers to desiccation. These two distinct roles of CHCs - as both desiccation barriers and recognition pheromones - are expected to produce different forms of selection, as the optimal molecular properties for the two functions are quite different. In this project functional genomics, chemical ecology, and behavioral ecology will be combined to test the overarching hypothesis that evolutionary trade-offs shape the recognition system of social insects. The results of this research will illuminate how genetic and chemical changes lead to changes in individual behavior and, in turn, alter the structure of complex societies.