Pheromone blend complexity in heliothine moths

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Insects, and particularly moths, rely heavily on sex pheromones as a means of odor-based communication to draw together opposite sexes. To date, thousands of sex pheromones have been identified, with each species having its own unique blend of chemicals which will attract a mate (typically produced by females to attract males of the same species). As such, there is incredible diversity in pheromone composition, but a poor understanding of the evolution and shifts in production, detection and preference of these chemicals as new species evolve and diverge from one another. This begs the question, “why are there so many unique pheromone blends?” Despite the wealth of documented pheromones in insects, science is still struggling to understand the mechanisms by which pheromone composition and preferences shift during speciation events (formation of new species), or if these features may, in fact, drive speciation. Understanding such shifts are paramount to our understanding of olfactory system function, and moreover, to adapting insect control strategies which use pheromones to monitor and control pests. This project will examine pheromone preference in the context of reproductive species isolation, along with neurophysiological correlates of pheromone detection and processing across related species of heliothine moths. Heliothine moths represent an excellent model system for examining divergence of pheromone production, and the mechanisms of detection and processing, by comparing closely related species. Specifically, divergence in olfactory communication is evident among heliothine species, based on shifts in the use of key components within each species' sex pheromone blend. These blends function to both attract members of the same species, and inhibit mating errors between closely related species. For example, a female sex pheromone component attractive to male conspecifics may be strongly antagonistic to males of other, closely related species. Eight species of moths will be examined in studies of pheromone composition, and tested for behavioral blend preference, along with receptor expression and neurophysiological mechanisms modulating such preference.By using a multi-faceted, integrated approach, which incorporates chemistry, physiology and molecular biology, we will build significantly upon the current knowledge of the evolution of pheromone-based species isolation, and basic olfactory processing. By exploring putative neural mechanisms which correspond with changes in pheromones, we can understand how complexity if selected for in pheromone blends. Through a better understanding of pheromone evolution, we will enable development of environmentally responsible insect management technologies for many species, thereby ensuring the health of Canadians and sustainability of agriculture and natural resources.