Signal and Response Coevolution - Specific Projects

• Signal and response coevolution in the two well-defined sex pheromone races
  of the European corn borer, Ostrinia nubilalis

Despite many years of research on the sex pheromone races in O. nubilalis, there are still two unsolved problems: 1) to identify the genes involved in female pheromone production and male response, and 2) to understand the evolution of pheromone divergence between the two races of O. nubilalis. To address these problems, in 2007 the Ostrinia consortium was formed between the Entomology and Neuroethology Departments at MPICE, the Biology Dept. of Lund University and the Dept. of Plant Protection of the Swedish University of Agricultural Sciences in Alnarp. By using QTL analysis, mapping of candidate genes and functional analysis, we recently identified the gene responsible for the strain-specific difference of female pheromone production (Lassance et al. 2010. Nature 466). Currently we are identifying the genomic locations of genes that control the male behavioral response to the differing pheromone blends. This research is conducted by the postdoc Dr. Melanie Unbehend.

Collaborators: Teun Dekker, Zolt Karpati, Fotini Koutroumpa

• Within-population variation in the sex pheromone of Heliothis virescens

We found the sex pheromone of the moth Heliothis virescens (Lepidoptera, Noctuidae) to be polymorphic in all populations studied so far; polymorphism within moth populations for chemical mating signals has not been observed before. In the laboratory we have selected for the two extreme types in this pheromone polymorphism (see Groot et al. 2014. Proc Royal Soc B 218), so that we are now in the unique position to determine what selective factors maintain the polymorphism. The specific projects that we are currently working on with these selection lines are: What is the genetic basis of the within-population variation? We are conducting QTL analysis on female-informative crosses and fine-scale mapping in male-informative backcrosses. Are there any hitchhiking effects when selecting for the extreme pheromone types, e.g. variation in male response, variation in development and performance on host plants? We are also assessing the preference and performance of hybrids.

• Close-range sex pheromone variation and its role in speciation

Both mechanistic and evolutionary studies of sexual communication in moths have concentrated on long-range sexual signaling – females emit a sex pheromone to which males are attracted. Courtship behavior, which includes emission of a close-range sex pheromone by the male, female assessment of the male, and ultimately acceptance or rejection of the courting male, has been investigated mainly in species in which males obtain pheromone or its precursors from plants and bias female choice with nuptial gifts. In most moth species, however, male close-range pheromones are synthesized de novo from similar precursors that are used by females to biosynthesize the female pheromone. In these moth species the male pheromone is important for species-recognition and female acceptance of males. We are addressing the following 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? (b) Is the production of male sexual signals linked to production of female signals in these species? This project is funded by NSF (award IOS-1052238). The research is currently conducted by two postdocs: Dr. Michiel van Wijk at UvA and NCSU, and Dr. Jeremy Heath at NCSU.

Collaborator: Coby Schal