Ficus racemosa is pollinated by a single population of a single agaonid wasp species in continental South-East Asia.

High specificity in the Ficus-agaonid wasp mutualism has lead to the assumption of a mostly 'one-to-one' relationship, albeit with some exceptions. This view has been challenged by new molecular data in recent years, but surprisingly little is known about local and spatial genetic structuring of agaonid wasp populations. Using microsatellite markers, we analysed genetic structuring of Ceratosolen fusciceps, the fig wasp pollinating Ficus racemosa, a fig tree species widely distributed from India to Australia. In sampling stretching from the south of China to the south of Thailand we found evidence for only a single pollinating wasp species in continental South-East Asian mainland. We found no evidence for the co-occurrence of cryptic species within our subcontinent sampling zone. We observed no spatial genetic structure within sites and only limited structuring over the whole sampling zone, suggesting that F. racemosa is pollinated by a single population of a single agaonid wasp species all over continental South-East Asia. An additional sample of wasps collected on F. racemosa in Australia showed clear-cut genetic differentiation from the Asian continent, suggesting allopatric divergence into subspecies or species. We propose that the frequent local co-occurrence of sister species found in the literature mainly stems from contact zones between biogeographic regions, and that a single pollinator species over wide areas might be the more common situation everywhere else.