The one-to-one species specificity of the Ficus-Agaoninae mutualism: how casual?

Abstract

The fig tree - fig wasp mutualism has long been considered to be strictly species-specific: each fig tree species is obligatorily pollinated by one fig wasp species, and each wasp species can only reproduce in one fig species. The first exceptions cited were thought to result from misidentifications of either figs or wasps, but as for most dogmas in biology, increasing knowledge of the mutualism has led to question the strict one-to-one rule. More and more examples of co-occurrence of at least two pollinators per fig species are provided from all over the world. I define below 6 categories of co-occurrence of more than one species of pollinators and 3 categories of pollination of different species of Ficus by the same species of pollinator. I give an accurate description of the state of our knowledge on the exceptions to the one-to-one rule in the different biogeographic regions and discuss the relatively high number of breakdowns to the rule, in South-Eastern Asia.