Species Divergence Between Salvia Honania And Salvia Meiliensis Of Sect.drymosphace

Salvia honania L.H.Bailey and Salvia meiliensis S.W.Su belong to the sect.Drymosphace（Lamiaceae）.The two species have highly similar morphological characteristics,mainly distributed in the Dabieshan Mountains bordered by Henan,Anhui,and Hubei provinces.There are still controversies in the definition of species between the two species.In this study,the morphological characteristics of the two species were observed and redescribed based on extensive field investigations.Based on 212 wild resource materials from 16 populations of the two species,five pairs of EST-SSR molecular markers,one pair of nuclear DNA markers（ITS）and three pairs of chloroplast gene（cpDNA）markers（rpl32-trnL,trnL-trnF,psbA-trnH）were used to explore the genetic variation and population speciation history of S.honania and S.meiliensis,and the species relationship between the two was defined.The main results of this study are as follows.（1）In terms of morphology,S.honania and S.meiliensis were diverse morphologically,and most of the diagnostic characteristics listed in the original literatures were not absolutely stable.In addition to the fact that the inner surface of the calyx of S.honania is white villous annulate while S.meiliensis is puberulent in all populations,the remaining traits cannot be absolutely used as morphological traits to distinguish the two species.（2）The polymorphism content（PIC）of 5 EST-SSR primers was 92.5%,and the genetic diversity was relatively high.The genetic differentiation coefficient(F_ST=0.253)indicates that the two species have undergone significant genetic differentiation.Molecular variance analysis（AMOVA）showed that genetic variation mainly occurred within populations.Mantel test results showed that there was a significant positive correlation between genetic distance and geographical distance,indicating that the genetic differentiation was affected by geographical isolation.The results of Neighbor-Joining tree（NJ）based on Nei’s genetic distance,Principal Coordinate Analysis（PCoA）,and Structure all supported that all populations were divided into two groups,including Group A and Group B.In Group A,all populations belonged S.honania while all populations of Group B were S.meiliensis.（3）Twenty haplotypes were detected based on nrDNA and 40 haplotypes were detected based on cpDNA.The Nst calculated based on the two datasets were significantly greater than Gst,indicating that all populations had obvious phylogeographic structure at the species level.The results of nrDNA haplotype analysis supported that S.honania and S.meiliensis were monophyletic and were sister species.Results from cpDNA data apparently conflicted with that from nrDNA data,which monophyly of the two species was not surported and some shared haplotypes were found between the two species.The gene flow between some geographically adjacent populations occured frequently（Nm>1）.The conflict between cpDNA and nrDNA maybe mainly resulted from gene introgression caused by hybridization between neighboring populations of the two species.In addition,chloroplast capture and incomplete linkage sorting may also be the cause of nucleocytoplasmic conflict.（4）Based on the haplotype study,the SH6 population（Jinlanshan,Henan province）may be the origin point of species differentiation or the refuge of populations during ice age,as well as the differentiation time was 1.94 Mya.This study supports the view that S.honania and S.meiliensis are two independent species.The two species are not completely isolated in reproductive isolation,and there is frequent gene flow between some neighboring populations,which may lead to interspecific hybridization.Lastly,the extreme climate of Pleistocene may have been an important driving force for the differentiation between the two species.