Figs (Ficus species, Moraceae) are defined by a unique enclosed inflorescence, the syconium, which are also the arena for interactions with fig wasps. Figs and their pollinating wasps constitute one of the classic examples of pollination mutualism and appear to present one of the best cases of co-evolution known. Figs are completely dependent on fig wasp for pollen dispersal and the production of viable seeds. For their part, the fig wasps are completely dependent on the fig for the completion of their life cycle.

Fig wasp are very small (1-2 mm) and short adult life spans (2-3 days). It is reported that fig wasps of monoecious figs, which are often large canopy tree species, can fly long distance by wind. For the ones of dioecious figs, which are small understory species and occur at high local population and flowering densities, are thought to fly short distance. The seeds of figs are mainly dispersed by bats and birds. Usually, they fly longer than fig wasps. So the seeds are more effective to gene flow among populations for dioecous figs.

We tested this prediction by using nuclear microsatellite (nSSR) and chloroplast sequence (cpDNA) data to infer the ratio of pollen to seed mediated gene migration (r) in F. hirta. Despite predictions we found low nuclear differentiation and high chloroplast differentiation among 15 sample populations separated by up to 2850 km. Taking into account differences in inheritance (biparental vs maternal) and ploidy (diploid vs haploid), the equilibrium estimate r =16.2-36.3 was far greater than expected for a species with restricted pollen dispersal.. We rectify this evidence of long-distance pollen migration and restricted seed migration with previously published data for dioecious figs. A paper was accepted in Molecular Ecology [H. Yu et al., 2010]