Mediation of a Mutualistic Conflict for Pollination via Fig Phenology and Odor Recognition between Ficus and Fig Wasp

Abstract

The vegetative and reproductive growth of plants provide the basic tempo for an ecosystem, and when species are interdependent, phenology becomes crucial to regulating the quantity and quality of the interactions. In plant–insect interactions, the plants signal the beginning of their reproductive period with visual and chemical cues; however, in the case of Ficus mutualism, the cues are strictly chemical. The volatile organic compounds emitted by a fig species are a unique, specific blend that provides a signal to mutualistic wasps that the figs are receptive for pollination. In this study, we studied both the phenological pattern of Ficus septica in Central Taiwan and its emissions of volatile compounds at receptivity. This dioecious fig species displays a pattern of continuous vegetative and reproductive production all through the year with a decrease in winter. In parallel, the odor blends emitted by male and female trees are similar but with seasonal variations; these are minimal during winter and increase with the size of the wasp population during the favorable season. In addition, the pollinating females cannot distinguish between the male and female summer odor blends. The link between odor similarity, pollinators and intersexual conflict is discussed.