Abstract:

Ficus is the keystone plant in tropical forests, and it also occurs in subtropical and even temperate areas. More than 700 species in the genus Ficus (Moraceae: Ficus) and their species-specific pollinator, the fig wasp, (Chalcidoidae: Agaonidae) has been discovered. The interactions between them, which have become an obligate mutualist relationship, have a very long evolutionary history. Pollen dispersal in figs is completely dependent on fig wasps, which enter the syconium where viable seeds are produced. Fig pollinators are uniquely dependent on the fig for the completion of their life cycle. Each fig species attracts its own species of fig wasp by emitting specific volatile compounds during their receptive period and these wasps lay their eggs in the developing ovary of the host fig species. As ovipositing female wasps simultaneously carry pollen from other syconia and pollinate figs actively or passively, they show peculiar morphological and behavioral adaptations to figs and a life cycle highly synchronous with fig inflorescence. Such specialization and interactions make diversity in species, genetics, morphology and behavior in pollinators and their host plants an exciting example for studying interspecific coevolution. Although fig-pollinator symbiosis is now widely regarded as a model system of plant-insect coevolved mutualism, little is known about the history and process of their interactions. Current experiments and observations have suggested the fig/fig wasp obligate mutualism (this is not a complete sentence but I am not sure what the author is trying to say here). However, present fig and fig wasp classifications, which are based on morphological characteristics and their interactions, are still incomplete and controversial. This short review summarized the knowledge and questions on coevolved mutualism, the molecular phylogeny of fig/fig pollinator symbionts and the traditional classification of Ficus. Studies on the interactions between fig/fig pollinator and re-classification of Ficus in China based on molecular phylogeny were also discussed. Research on the phylogeny of about 100 species of fig trees, which mainly occur in tropical and subtropical areas in China, has just started and only a few reports on fig pollination biology and ecology exist. Much work should be done to make a thorough study of both symbiotic partners. Though systematic classification of Ficus is the basis of the coevolutionary study, application of molecular phylogeny is also necessary and feasible, which will promote further research and understanding of plant-insect coevolution in China.