Investigation Of Genetic Admixture Between Castanopsis Sclerophylla And Castanopsis Tibetana Based On Microsatellite Markers

Castanopsis sclerophylla is one of a species of Fagaceae,as well as Castanopsis tibetana.They are dominant species in the evergreen broad-leaved forests widely distributed in many provinces,such as Zhejiang,Fujian,Jiangxi,Hunan,Guangxi,Guizhou and so on.They both have ecological value,economic value and can be made into medicine.One researcher had collected one specimen of Castanopsis tibetana×sclerophylla in 1957,which had been the only sample ever found.It was once listed as a separate species by the Flora of China,while it had been discarded from species when the Flora of China revised into English.C.tibetana×sclerophylla(Castanopsis tibetana×sclerophylla)could be an ideal experimental for studying weather C.sclerophylla and C.tibetana can occur interspecific hybridization in natural environment.With the development of molecular marker technology,the research about plants covers from macroscopic phenotypic differences to microcosmic genetic level.People found that natural hybridization is a quite common phenomenon and happened frequently in the angiosperm,which has played an important role in evolution.Analysis of natural hybridization provides insights into the process of speciation.While gene introgression has long been thought to threaten species,especially the endangered species,it still has a list of positive effects.Recent research suggests that these processes are potential resources during evolutionary selection of species.They can generate new genotype combination,increase genetic diversity,improve the ecological adaptation of species and promote population expansion.C.sclerophylla,C.tibetana and C.tibetana×sclerophylla are selected as the subjects investigated,using microsatellite markers to analyse 215 DNA samples that collected from natural populations.The research discussed genetic diversity,population genetic structure and interspecific hybridization.12 SSR markers of high polymorphism and well amplified are used in the analysis of total 214 individuals,of which 152 alleles were detected,and the mean number of alleles(Na)is 12.6667,mean effective number of alleles(Ne)is 4.9307,mean value of Shannon information index(I)is 1.7875,mean value of observed heterozygosity(Ho)is 0.4608,mean value of expected heterozygosity(He)is 0.7709.Genetic differentiation coefficient()is at medium level.of C.sclerophylla(0.0734)is lower than that of C.tibetana(0.0958),indicating that more genetic variation occurred between C.tibetana populations.Gene flow(Nm)of C.sclerophylla(3.1556)is higher than C.tibetana(2.3608).Model-based clustering method was implemented in the program STRUCTURE,in which 2 clusters was given based on the value of △K.The results of clustering indicate that C.tibetana×sclerophylla is the hybridization offspring of C.sclerophylla and C.tibetana.What’s more,there are also four natural hybrids which accounted for 1.402%,providing evidence of hybridization happened in other populations between C.sclerophylla and C.tibetana.In summary,the results of analysis of experimental data revealed a high genetic diversity and limited interspecies hybridization between C.sclerophylla and C.tibetana in nature.Our results can offer implications for further study of gene flow and succession tendency.