Phylogeography Of Camellia Nitidissima

Camellia nitidissima Chi which belongs to Camellia(Theaceae)distributed in South China and North Vietnam.Two separate geographical distributions of C.nitidissima have been found in China: one is in the Fangcheng area,located southeast of Mount Shiwan,and the other is in the Nanning area,located south of Mount Xidaming.C.nitidissima includes two varieties,C.nitidissima var.nitidissima and C.nitidissima var.microcarpa.It has high ornamental value and medicinal value.Driven by economic interests,wild C.nitidissima individuals were destructively transplanted and have been unable to be found in the wild.var.nitidissima and var.microcarpa were classed as Near Endangered and Endangered.In this study,A total of 91 individual plants from 9 populations across the entire distribution range in China were analyzed using three DNA sequences: a chloroplast fragment(cpDNA),two single-copy nuclear DNA(nDNA)sequences,phenylalanine ammonia-lyase(PAL)and intron 23 of the RPB2 gene(RPB2).By combining these three types of markers,we investigated the genetic diversity and genetic structure of C.nitidissima.Based on the above result,we uncovered the mechanism of formation of the current disjunctive distribution of C.nitidissima in China and the factors affecting the genetic structure of var.nitidissima.Finally,protection strategy were proposed.The main results were as follows:1)The length of the aligned cpDNA sequences was 5190 bp,this contained 13 polymorphic sites for seven haplotypes(i.e.,C1–C7)identified.The haplotype network and ML tree of cpDNA revealed that the cpDNA dataset of C.nitidissima can be partitioned into two groups which corresponded to the Fangcheng and Nanning areas.The two groups corresponding to the two areas were also resolved,in the SAMOVA results of var.nitidissima.The nuclear DNA sequences PAL and RPB2 were respectively 661 bp and 960 bp in length.For PAL,27 polymorphic sites identified 20 haplotypes(i.e.,H1–H20).For RPB2,20 haplotypes(i.e.,R1–R20)were defined by 41 polymorphic sites.The SAMOVA results that PAL and RPB2 dataset of var.nitidissima can be partitioned into two consistent groups.The two population groups also matched the species geographical distribution-except for population BB.Considering the groups based on the SAMOVA results for nDNA,variation existed between two groups(34.67% for PAL and 29.26% for RPB2)is consistent with a prior study that used the AFLP marker finding 36.09% variation between two geographical groups(no BB population).2)Chloroplast and nuclear(PAL and RPB2)datasets all demonstrated a moderate level of genetic diversity of C.nitidissima(cpDNA,n=7,h=0.837,?=0.00082;PAL,n=20,h=0.858,?=0.00557;RPB2,n=20,h=0.884,?=0.00857).3)In PAL haplotype network,H11,unique to Fangcheng area,had the characteristics of the ancestral haplotype.Meanwhile the star phylogeny of the haplotypes indicated the common expansion of H11.This results suggests an expansion occurred from south(Fangcheng)to north(Nanning)to form these two geographical distribution areas.An interpretation that is also consistent with the known expansion direction of Camellia and sect.Chrysantha chang(Camellia).4)There are no sharing haplotype between var.nitidissima and var.microcarpa based on cpDNA,PAL and RPB2 sequences.That indicated a high genetic differentiation between var.nitidissima and var.microcarpa.The R2–R5 were unusually divergent,separated from other haplotypes by at least 10 steps in the RPB2 network diagram.This suggests that R2–R5 may have been transferred from other species of Camellia by interspecific hybridization and introgression.interspecific hybridization and introgression may lead to the genetic differentiation between var.nitidissima and var.microcarpa.5)The long period of geographic isolation may led to high genetic differentiation of var.nitidissima between the Fangcheng and Nanning areas.In addition,Introgression may promote the genetic differentiation of var.nitidissima in Nanning area.Based on the PAL and RPB2 network diagram,populations CF and CFH which distributed in Nanning area were likely to introduce other Camellia species in Nanning via introgression.Introgression did not occur in population BB.Therefore,introgression promoted high genetic differentiation between BB and other populations in Nanning.6)Our genetic data clearly show that per population had at least one unique haplotype,all populations ofshould be protected.A high genetic differentiation were existed between var.nitidissima and var.microcarpa.var.microcarpa should be recognized as one management unit.At the wild distribution point of the var.microcarpa,only fonding seedings.Therefore,var.microcarpa should be protected in situ.var.nitidissima should be recognized as three management units.one including CL,CN,CJ and CD populations in the Fangcheng,one including BB in Nanning,with another group consisting of CF,CFH and CR populations in the Nanning area.In the field survey,there is no wild individuals in population BB and CR distribution points.Only a small number of adult plants are transplanted in local residents' homes.Therefore,some individuals should be migrated to the germplasm resource bank.