Our lab has been collaborating with Fred Gould's and Astrid Groot's labs to understand the chemical ecology of two closely related moth species that can be hybridized, Heliothis virescens and H. subflexa.
Most night-flying moth species locate mates through production of, and response to, a very precise blend of volatile chemical compounds. Within a population, females with atypical blends are less attractive to males than females with the population's common blend. Similarly, rare males that respond to atypical blends are expected to be at a disadvantage in finding mates. The genes that control pheromone blend ratios appear to not be linked to, or affect male response, so mutations that cause changes in each of the two components of communication are expected to arise independently. We have been examining pheromone blend ratios and male responses by moving sexual communication genes between the two species. Molecular markers developed in the Gould lab are used to map quantitative trait loci (QTL) that control the relative concentration of a number of female pheromone components and male responses that differ between the two species. By use of repeated backcrossing we have created strains that are largely genetically identical to one species, but express pheromone production alleles from the other species. Astrid Groot is testing these lines for mating success with the parental lines. Our long-term goal is to determine the impacts of single genetic changes on sexual communication.
A new NSF-funded project with Astrid Groot (Max Planck Institute for Chemical Ecology [MPICE] in Jena, Germany, and University of Amsterdam) concentrates on male pheromones, which are important for species‐recognition and female acceptance of males. Despite the recognition that males invest disproportionately in the tissues that produce these pheromones, their roles in advertising male quality and guiding female mate choice have not been considered. This project addresses two major questions: (a) How does natural variation in close‐range sexual signals affect female choice in moth species where the male pheromone resembles the female pheromone? and (b) Is the production of male sexual signals linked to production of female signals in these species? Specifically, we will: (1) chemically identify the close‐range male pheromones in two moth species (fall armyworm Spodoptera frugiperda, and tobacco budworm Heliothis virescens), (2) quantify the magnitude of between‐strain intraspecific variation in the male pheromones, and (3) evaluate what variable features of the male pheromone contribute to female choice.
Hairpencils of male Heliothis virescens