Figs and pollinating fig wasps form an extreme obligate pollination mutualism. Increasing evidence suggests that pollinator sharing and hybridization occurs among fig taxa, despite relatively strict coevolution with the pollinating wasp. Therefore, the fig–fig wasp system would be an ideal group to evaluate how pollinator sharing and hybridization affect the plant species identity and the co-diversification of plants and their pollinators.
   Prof. CHEN Jin’s team of Xishuangbanna Tropical Botanical Garden (XTBG) used five Ficus taxa in two Asian sections (Sycomorus and Hemicardia) and their pollinating fig wasps as study materials. They combined observational and experimental methods (molecular genetics, chemical composition and pollinator preference tests) to examine the prevalence of pollinator sharing and interspecific gene flow within a suite of sympatric and closely related fig taxa. They aimed to evaluate the pattern and causation of pollinator sharing and inter-taxa gene flow among sympatric fig taxa.
   They addressed the questions that to what extent pollinator sharing or pollinator shifts occurred among sympatric dioecious fig taxa and how the degree of pollinator sharing related to inter-taxa gene flow among sympatric host figs. They further tested how the fig volatile signature influenced pollinator behaviour among fig taxa, in terms of host recognition and pollinator sharing.
   They found that all five fig taxa shared pollinators with other taxa and gene flow occurred between fig taxa within and between sections. Floral volatiles of each taxon attracted more than one pollinator species. Floral volatiles were more similar between closely related figs, which experienced higher levels of pollinator sharing and inter-taxa gene flow.
  The study demonstrated that pollinator sharing and inter-taxa gene flow were rather common among closely related sympatric dioecious fig taxa and that pollinators chose the floral volatiles of multiple fig taxa. The patterns might be mainly caused by the inter-taxa similarity of fig floral volatile signatures during the receptive phase and the floral volatiles' attractiveness to multiple pollinators.
The study was funded by the National Natural Science Foundation of China (31400329 and U1402264), West Light Foundation of Chinese Academy of Sciences and the Chinese Academy of Science 135 program (XTBG-T01).
  The study entitled “Pollinator sharing and gene flow among closely related sympatric dioecious fig taxa” has been published online in Proceedings of the Royal Society B: Biological Sciences.

Contact
Prof. CHEN Jin, Ph.D Principal Investigator
Key Laboratory of Tropical Forest Ecology, Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, Mengla, Yunnan 666303, China
Tel: 86-691-8715457
E-mail: cj@xtbg.org.cn

Percentage pairwise migration rates for five sympatric morphologically distinct fig taxa estimated in BayesAss.

(Image by WANG Gang)