| Global climate fluctuation and environmental differences have a profound impact on the genetic differentiation and geographical distribution pattern of species.China's complex geographical environment and rich species diversity make it an ideal area to study species differentiation and geographical pattern formation.Allium macrostemon Bunge is a perennial herb widely distributed in all provinces of China.It is a good material for studying the geographical distribution pattern.In order to elucidate the effects of environmental heterogeneity and climate fluctuation on the level of genetic diversity,genetic differentiation and geographical distribution pattern of A.macrostemon population,genetic variation and genetic structure were studied using SSR.Also,phylogeography of was studied based on cp DNA sequence and nr DNA sequence.Furthermore,phylogeny was studied using GBS.The main results were as the follows:1.The genetic diversity and genetic structure of A.macrostemon were studied based on 5 pairs of fluorescent SSR primers.The results showed that:(1)A.macrostemon showed a high level of genetic diversity at the species level.The effective number of alleles(Ne),expected heterozygosity(He)and Shannon information index(I)of A.macrostemon were 2.357,0.498 and 0.871,respectively.(2)AMOVA analysis showed that A.macrostemon had a high level of genetic differentiation(Fst=0.238).(3)The Mantel test showed that there is a significant correlation between geographical distance and Nei's genetic distance,indicating geographic isolation among populations of A.macrostemon.(4)The results of structure analysis were almost consistent with the results of the NJ phylogenetic based on Nei's genetic distance,and the A.macrostemon populations could be divided into three geographic groups:the northern region,the southwest region and the central-southeast region,which were basically consistent with the results of neighbor tree based on Nei's genetic distance.2.cp DNA(rps16,trn L-F and psb A-trn H)and nr DNA(ITS)were used the phylogeography of A.macrostemon.The results showed that:(1)42 chloroplast and65 ribosomal haplotypes were identified in 50 populations,respectively.And chloroplast haplotype H1 and ribosomal haplotype H7 were predominated and was present in 50 populations.(2)A.macrostemon showed high level of genetic diversity and differentiation.The total genetic diversity was significantly higher than the average genetic diversity within populations(cp DNA:HT=0.860,HS=0.121;nr DNA:HT=0.967,HS=0.186).The AMOVA revealed that the total genetic variation came from among populations.(3)There were high haplotype diversity and nucleotide diversity in some populations from northern,central-southeast and southwest regions of China,suggesting that there might be two or more shelters in A.macrostemon during the glacial period.3.The genetic evolution and phylogeny of A.macrostemon were studied by GBS.The results showed that A.macrostemon was a monophyletic group,which could be further divided into three groups:northern region,central southeast region and southwest region.The A.macrostemon with similar geographical origins belong to the same group,and it is believed that the geographical distance of A.macrostemon was closer if its genetic distance is closer.In conclusion,based on GBS,SSR,cp DNA and nr DNA data on genetic differentiation and geographical distribution pattern of A.macrostemon from different habitats,supporting the division of A.macrostemon into three subline:northern region subline,central southeast region subline and southwest region subline.The current geographical distribution pattern of A.macrostemon was probably influenced by geographical environment and climatic fluctuations.The results of this study provide a reference for further studies on the effects of complex geological conditions and climatic fluctuations on the genetic diversity,genetic structure and phylogeographic pattern of widespread species in China were provided for reference. |
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