The Phylogenetic Study Of Subgenera Urostigma And Sycomorus Figs And Their Pollinating Wasps

Figs (Ficus spp., Moraceae) and fig pollinating wasps (Agaoninae, Agaonidae, Chalcidoidae, Hymenoptera) form the most specialized obligate mutualism during the long evolution history, which has been treated as the model system to study co-evolution, co-speciation and co-divergence. Previous molecular phylogenetic studies have provided some support for cocladogenesis and coadaptation between pollinating wasps’genera and their respective fig sections. However, existing studies on the fit of pollinator and host phylogenies show that the relationship between fig and their pollinators is not always so prescribed. Chinese Ficus distributional area is at the ndrthern edge of the India-Australian distributional center. There are all the six subgenera species and some endemic species in China. Here, we reconstructed the phylogenetic relationships of figs and fig pollinating wasps including Chinese species by using maximum parsimony and Bayesian methods, and estimated their divergent times in BEAST for the first time. We obtained 38 ITS,30 ETS and 33 G3pdh sequences of 35 Chinese figs species, and 50 COI and 48 Cyt b sequences of 39 pollinating wasp species. In addition,181 ITS,151 ETS,124 G3pdh (2 outgroup species), and 143 COI sequences (4 outgroup species) were directly downloaded from GenBank. As a result, a total number of 219 ITS,181 ETS,157 G3pdh, and 193 COI sequences were used in the final analyses.The results of combined ITS-ETS-G3pdh dataset and COI dataset showed that section Pharmacosycea and their related Tetrapus pollinating wasps are the most ancient species. Subgenus Urostigma (excluding section Urostigma), subgenus Sycomorus, subgenus Sycidium and subgenus Synoecia are monophyly, and each section is clustered into one group with great support. On the whole, the pollinating wasp species of each genera group together in the analyses. The passively pollinating genus Tetrapus is the most ancient species, and the Blastophaga and Wiebesia pollinators of dioecious Ficus are more primitive than others. Both Blastophaga and Wiebesia are not monophyletic. Although the section Urostigma figs did not group with the other species of subgenus Urostigma, its pollinators fall in one clade with other Urostigma pollinators. We analyzed the fig and pollinating wasp relationship among sections Conosycea and Urostigma of subgenus Urostigma, and among subgenus Sycomorus respectively. Our results showed that there is no strict coevolution and cospeciation between figs and fig pollinating wasps, even at the scale of wasp genera and associated fig subgenera and sections, and pollinator host-switching is a more common phenomenon in this mutualism.The biogeographic divergent times estimations results showed that the origin and divergence of Ficus and fig pollinating wasps are corresponding to two mass extinctive events (the Late Cretaceous Cenomanian-Turonian biotic crisis and Cretaceous-Tertiary (K/T) extinction). Moreover, our reconstruction shows the Afrotropical and Neotropical species originated from India-China continent ancestors with subsequent dispersal back from Africa to Old World.Ficus prostrata Miq. and Ficus semicordata J.E. Smith should be classified into section Hemicardia, subgenus Sycomorus, based on the phylogenetic results and the classification of Berg’s. The molecular data analyzed results of Ficus auriculata Lour., Ficus oligodon Miq., and Ficus sp. suggest that Ficus auriculata and Ficus oligodon are same species, but Ficus sp. is one different species. Their related pollinator species are closely related and originated from same ancestor. However, the pollinators of these figs are the same species in same location, while the pollinator species are different among locations. It suggested that the ancient wasp have evolved into different species in different habitats due to biogeographic isolation.