1Centre d' Ecologie Fonctionnelle et Evolutive (CEFE-CNRS), 1919 route de Mende, 34293 Montpellier Cedex 5, France.
2Department of Chemistry, University of Brunei Darussalam Bandar Seri Begawan 2028, Brunei (SE Asia).
In symbiotic mutualisms with horizontal transmission, encounter of partners is an often risky process that must be repeated with each new generation. In one group of such mutualisms, those between figs and their pollinating wasps, we have demonstrated the role of volatile compounds released by receptive figs in the attraction of pollinators. Beyond contributing to our understanding of ecological interactions in this fascinating mutualism, our studies of floral scents in this system allow approaches to questions of general importance in the evolutionary ecology of species interactions: (1) It has been suggested that pairwise coevolution is rare in associations with horizontal transmission, and that "exclusion filters" are necessary for enforcing the specificity required for strong pairwise interactions. What is the role of fragrances in evolution and maintenance of specificity in the 800 "copies" of the fig/wasp mutualism? (2) Pollination in dioecious figs requires that pollinators enter female figs, in which they die without laying eggs. Mechanisms for the evolutionary stability of dioecious fig/pollinator mutualisms are still unclear. Does intersexual chemical mimicry in floral scents play a role? These two questions will be discussed in light of our results on volatile compounds emitted by receptive figs in fig species-rich forests in Borneo.