Premier Presentation: Diversity of interactions in mutualism-centered plant-insect symbioses: The case of figs and fig wasps

Figs are keystone tree species in tropical and sub-tropical forests. The keystone status of figs is due to their peculiar biology in which the highly fig-species specific pollinators of figs, which are tiny fig wasps, breed only within enclosed globular fig inflorescences called syconia. In order to maintain fig wasp populations year-round, fig trees flower throughout the year; consequently, ripe fig fruit are also available to frugivores year-round, making fig trees a keystone species for species dependent on syconia and ripe fig fruit even in highly seasonal tropical forests. Fig syconia host the development of pollinating fig wasps, fig seeds, and also several parasites. These parasites can be non-pollinating fig wasps that are small or large gallers, as well as ecto- and endo-parasitoids that have a koinobiont, idiobiont or mixed life history strategy. Other parasites include nematodes that are either plant-parasites or wasp parasites and use female pollinating wasps as phoretic vehicles to move from one fig syconium to the other. Gallers accelerate while parasitoids retard the development of the syconium. Pollinating fig wasps compete with each other and with gallers for oviposition sites within syconia; non-pollinating gallers facilitate the survival of pollinators by serving as prey for parasitoids. We demonstrate the balance between a variety of factors such as syconium size, gall size, gall nutrition, syconium inhabitants and syconium availability on the maintenance of the diversity of interactions within this nursery pollination system. By using the syconium as a microcosm and focussing attention on the life-history traits of all the inhabitants of these microcosms and the various direct, indirect and feedback interactions, our findings have general implications for understanding the complex ecology of mutualism-centred communities in tropical forests.