Infection Pattern Of Wolbachia In Fig Wasp Community On Ficus Auriculata

Figs (Moraceae: Ficus) and fig wasps (Insecta: Hymenoptera: Chaleidoidea) has beenknown as a classic example of co-evolution, and become the focus of researches on origin andevolution of mutualism, resource conflicts, the stabilization of mutualism, sex ratiodistribution. In this system, the complex fig wasps community, extreme sexual dimorphismand male polymorphism challenge fig wasps classification.In this thesis, we introduced aDNA barcoding technique. By sequencing the general standard cox1fragement, we can fastand accurate identification of fig wasps species.Wolbachia symbionts are widespread intracellular bacteria that are found in arthropodsand nematodes. This maternally inherited endosymbiont could manipulate a lot ofreproductive processes in host, including incompatibility (cytoplasmic incompatibility),parthenogenesis, feminization, and male killing. It was proposed that CI may promote the hostspeciation. Several studies showed that hymenopteran more easy to infect Wolbachia,especially the higher infection rate in fig wasps and frequent horizontal transmission amongdifferent species. When Wolbachia and host mitochondrial haplotype exist linkagedisequilibrium, the host mitochondrial polymorphism should be changed, and then influencethe phylogeny based on mtDNA. The deeper research into the Wolbachia infection will helpus to learn more about Wolbachia transmission and the connection with diversity of species,and then more understanding the complex interaction and co-evolution of fig waspscommunity.Here we studied the mtDNA polymorphism and Wolbachia infection of fig wasps onFicus auriculata and Ficus oligodon. Samples were collected from5different locations inDanzhou Campus, Hainan University, Yingge Mountain, Changjiang, Jin Tang and Xishuangbanna arboretum, Yunnan. Combining morphological identification with molecular markers,we found that the galler on the male syconia and the galler on the female syconia actually aredifferent species. And they are not sister species, with mtDNA divergence up to80%andITS2gene divergence up to74.26%. The gallers showed very higher mtDNA polymorphismfrom different locations. We also discussed the impact of geographical distribution on thecurrent programme of fig wasp taxonomy based on DNA barcoding. Additionally, through thecox1gene molecular clock time tree, we estimated that two Apocryptophagus gallers divergedabout5.2million years ago.Alignment of ITS2sequences corrected by structural information showed that helixes Iand IV are the most conserved, whereas helix II is the most variable. The nucleotide composition (G+Ccontent) is similar among all species analyzed, except forApocryptophagus sp.2with instability secondary structure and higher G+C content. Furthermore, we also obtain the ITS gene (ITS1+5.8S+ITS2) from pollinating fig wasp Ceratosolenemarginatus and non-pollinating fig wasp Sycoscapter sp.1and Philotrypesis sp.1, showeddifferent gene type among different species, and conserved region in the same species, whichis a high-efficiency molecular marker.Tajima’s D test suggest that the mtDNA molecular diversity of Sycoscapter sp.1onFicus oligodon deviating from the neutrality evolution. In addition，the population sizechanges analysis demonstrate multiple peak distribution, ruled out the possibility ofpopulation expansion. Other groups of fig wasps accord with the neutrality evolution.Among all species analyzed, the Wolbachia infection is100%. Using MLST and wspgene, we obtained the ST from Profiles database, and confirmed3different strains: wMel、wHa and A_NY_Calyp150744c. The strains infection is also in connection with mtDNApolymorphism. For instance, the group mono-infected strain wMel of Apocryptophagus sp.2showed high mtDNA polymorphism. However, double-infected group showed low mtDNApolymorphism. In Apocryptophagus sp.1, the group mono-infected strain wMel showed thehighest mtDNA diversity, Obviously, the group mono-infected strain A_NY_Calyp150744cshowed the lowest mtDNA diversity. When double-infected, mtDNA polymorphism isintermediate.The infection of all gallers species analyzed, even from different locations, had noconnection with the interaction among the gall/seed figs and female/male gallers. Theinfection of wMel strain showed significant divergence, such as YGL and DZ, YGL and BN,and the YGL and JT. However, the other strains and multiple infection did not showsignificant divergence on different geographic locations.From the phylogenetic tree of the strains, we conjectured that there two transmissionmodels among fig wasps: strain wMel could high-efficiency vertical transfer and broadlyhorizontal transfer. On the contrary, in Ficus oligodon figs, the population of Sycoscapter sp.1just infected strain wMel; the population of Ceratosolen emarginatus infected all three strains,obviously, though the two fig wasp specis had closely ecological connection with each other,the horizontal transmission of the strains wHa and A_NY_Calyp150744c3had not yetoccurred.