Phylogenetic relationships, historical biogeography and character evolution of fig-pollinating wasps.

Nucleotide sequences from the cytochrome oxidase I (COI) gene were used to reconstruct phylogenetic relationships among 15 genera of fig-pollinating wasps. We present evidence supporting broad-level co-cladogenesis with respect to most but not all of the corresponding groups of figs. Using fossil evidence for calibrating a molecular clock for these data, we estimated the origin of the fig-wasp mutualism to have occurred ca. 90 million years ago. The estimated divergence times among the pollinator genera and their current geographical distributions corresponded well with several features of the break-up of the southern continents during the Late Cretaceous period. We then explored the evolutionary trajectories of two characteristics that hold profound consequences for both partners in the mutualism: the breeding system of the host (monoecious or dioecious) and pollination behaviour of the wasp (passive or active). The fig wasp mutualism exhibits extraordinarily long-term evolutionary stability despite clearly identifiable conflicts of interest between the interactors, which are reflected by the very distinct variations found on the basic mutualistic theme.