Coevolution of reproductive characteristics in 12 species of New World figs and their pollinator wasps

Abstract

1) Figs (Ficus) and fig-pollination wasps (Agaonidae) are highly coevolved mutualists that depend completely on each other for continued reproduction. However, their reproductive interests are not identical. 2) The natural history of their interaction often permits the direct measurement of total lifetime reproductive success of the wasp and of major components of reproductive success for the fig. 3) Data from 12 monoecious species of New World figs (subgenusUrostigma) and their wasp pollinators (Pegoscapus spp.) indicate that fig fruit size (number of flowers per fruit), wasp size, and the number of foundresses that pollinate and lay eggs in any given fruit interact in complex but systematic ways to affect the reproductive success of both the wasps and the figs. 4) Different aspects of the interaction may work against the reproductive interests of either the wasp or the fig, or often, both. For example, in some species an ‘average’ foundress may only realize 25% of its reproductive potential due to the high average number of foundresses. However, that same crowding slects for more male-biased sex ratios in the wasps that reduce potential fitness gains through pollen dispersal for the fig. Nonetheless, the natural distributions of numbers of foundresses per fruit more clearly reflect the reproductive interests of the figs than of the wasps. 5) Generally, it appears that most of the fig species studied can be arranged along a continuum from those with physically small fruits that produce a relatively low proportion of viable seed butt are very efficient at the production of female wasps to physically large, relatively seed-rich fruits that are relatively inefficient at producing female wasps. The implications of these findings for the coevolution of figs and their wasps are discussed.