The fig wasps associated with Ficus microcarpa, an invasive fig tree

Fig trees and their pollinating fig wasps represent one of the most species-specific mutualistic systems with a long history of co-evolution. Besides the pollinators, figs are also exploited by numerous non-pollinating fig wasps (NPFW). A few fig trees have become established outside their native ranges, and Ficus microcarpa, a monoecious fig tree, has become widely invasive, due to the widespread introduction of its specific pollinator, Eupristina verticillata. In this thesis, a global study was carried out to unravel the distribution and community structure of fig wasps associated with F. microcarpa. The work also examined which NPFW are potential bio-control agents and whether the plant is invasive due to reduced seed and pollinator predation in its introduced range (the 'enemy release' hypothesis).

At least 43 fig wasp species utilize F. microcarpa figs with more than 20 species present in the plant's introduced range. In newly established NPFW populations, a lack of male fig wasps at low population densities can cause Allee-like effects for fig wasps, but inter-specific facilitation is able to mitigate them. Generally, parasitoids were far less diverse than phytophages in the tree's introduced range with significant latitudinal effects on species richness. We unraveled the food web of fig wasps where sycoryctines (Pteromalidae) were parasitoids of agaonids, and eurytomids were parasitoids of epichrysomallines. A large galler species, Meselatus bicolor, is independent of the pollinator and can suppress both male and female reproductive successes of figs via competition for nutrients and preventing pollinators from entering figs. It may be an ideal bio-control agent. Enemy release in the introduced range failed to increase the plant's seed production but benefited the pollinator, and the greater survival of pollinator larvae in more peripheral galls emphasises the role of parasitoids in maintaining the fig-pollinator mutualism in monoecious figs.