Genetic Structure Of Ficus Sarmentosa Var. Henrvi In Eastern China And The Gene Introgression Between Ficus Pumila And Ficus Sarmentosa Var. Henrvi

Gene introgression is an important mechanism of evolution and non-isolated speciation. Two sympatric species have the same haploid type indicates gene flow between them. As one of the representative of the most obligate mutualism, fig trees and their wasps match very well in phenology, morphology and physiology. Previous studies showed that fig wasps are specific to their host, following "one to one" rule strictly. But recent researches using molecular methods to construct the phylogenetic trees revealed that the relationship between figs and their pollinating wasps are more complicated. And even observation experiment which is more direct evidence than phylogenetic trees proved the host shift phenomenon in this system. By studying gene introgression in the specialized system between figs and their wasps, we can have more comprehensive information in coevolution and understand the impact of introgression.Three kinds of molecular markers(cpDNA, nrITS, nDNA SSR) were used in the study to analyze the genetic structure of Ficus sarmentosa var. henryi in eastern China, while two of them(cpDNA, nrITS) were combined with Ficus pumila data to estimate the place and direction of gene introgression between the two Ficus species, and the genetic diversity were compared between the introgression populaion and non-introgression one. Main conclusions are as follow.1) Gene introgression between Ficus sarmentosa var. henryi and Ficus pumila happened in TL population, from the former to the latter, and after hybridization, the crossing offspring kept backcrossing to the Ficus pumila for some time.The severe situation in peripheral populations and the similar florescence make the introgression possible.2) No obvious substructure were found in Ficus sarmentosa var. henryi from eastern China. The result of cpDNA data revealed sudden expansion, which is similar to the pattern Ficus pumila in the eastern population, suggesting that they may have similar route of expansion after the ice age. The value of FsT is 0.055, which is close to the results in previous research in other Ficus, so we speculate that the flyability of its wasps is common.3) Compared to non-introgression population, the genetic diversity in introtression population is lower, especially in Ficus pumila, the genetic diversity parameters of TL is the lowest among all populations, while Ficus sarmentosa var. henryi in introtression population still has low diversity but not as remarkable as that in Ficus pumila. We suggestted that limited gene flow is the main reason that cause low genetic diversity.