Putting the puzzle together: the relationship between floral characters and pollinator morphology determines pollination mode in the fig-fig wasp mutualism.

Abstract

The diversification of angiosperms has largely been attributed to adaptive radiation of their pollination and mating systems, which are relevant drivers of the macroevolution processes. The fig (Ficus, Moraceae) and fig wasp (Agaonidae, Hymenoptera) interaction is an example of obligate mutualism. Passive and active pollination modes have been associated with morphological traits in both partners. However, more information is required to assess the relationship between floral traits and pollination modes, particularly in Neotropical Ficus species. This study evaluates the morphological traits of figs and fig wasps regarding pollination modes in species belonging to Neotropical Ficus sections (three species each of Americanae and Pharmacosycea). Pollination mode was identified by floral morphology, anther/ovule ratio, and specialized structures fig wasps use for pollen transport (pollen pocket and coxal combs). Fig species in sect. Americanae are actively pollinated because pistillate flowers form a synstigma, present anther/ovule ratios <0.11, and their pollinator Pegoscapus fig wasps have pollen pockets and coxal combs. In contrast, species in sect. Pharmacosycea have free pistillate flowers, with anther/ovule ratios >0.27; they are pollinated by Tetrapus wasps, which lack specialized structures to carry pollen. Each species of Ficus was associated with a single morphospecies of fig wasp. The results support previous contributions that consider reciprocal morphological traits between fig species and their pollinating wasps as evidence of a close co-evolutionary history.