Species-specific aggregation pheromones contribute to coexistence in two closely related thrips species

Pheromones play an important role in mediating interspecific interactions in insects. In an insect community, pheromones can reveal information about the senders, which could be used by other members of the food web (competitor, natural enemies, etc.) to their own advantage. The aggregation pheromones of two closely related thrips species, Frankliniella occidentalis and Frankliniella intonsa, have been identified with the same major compounds, (R)-lavandulyl acetate and neryl (S)-2-methylbutanoate, but in different ratios. However, the roles of the aggregation pheromones in the interspecific interactions between these two closely related species are unknown. Here, we investigated the roles of major aggregation pheromone compounds in interspecific interactions between F. occidentalis and F. intonsa for both long and short ranges. The results showed that, at tested doses, neither aggregation pheromone- induced long range cross-attraction nor short range cross-mating was detected between F. occidentalis and F. intonsa. Field-trapping trials showed that the speciesspecificity in aggregation pheromones was regulated by the ratio of two major compounds. However, species-specific blends of the two major compounds had no effect on short-range interactions between these two species. Our data from the thrips species provide support for the ` aggregation model of coexistence', explaining the species- specific pheromone-mediated coexistence of closely related species. Thus, species-specific pheromones could be one of the factors affecting population dynamics and community structure in closely related insects with similar niches.