Phylogeography Study On The Rare And Endangered Plant Isoetes Yunguiensis

Isoetes yunguiensis Q.F.Wang et W.C.Taylor is an ancient relict Lycopodium plant only distributed in the Yungui Plateau,which is similar to the same genus in appearance.In this study,the genetic diversity and genealogical structure of I.yunguiensis were revealed by EST-SSR molecular marker and noncoding region sequence of chloroplast,and the potential distribution regions in different periods were predicted by Max Ent v3.4.The main contents and conclusions are as follow:(1)According to the field investigation,the number of wild populations of I.yunguiensis is 14,and only 3 populations have more than 500 plants,and the total number of plants is less than 6,000.(2)Based on the study of EST-SSR molecular markers,CX population has the highest genetic diversity(He = 0.591)and XLC population has the lowest genetic diversity(He = 0.335).UPGMA cluster analysis shows that 14 populations can be divided into two groups,which is consistent with the results of principal coordinate analysis and structure cluster analysis.(3)Based on sequence of three cp DNA noncoding regions,the Ht = 0.631,and the Hs = 0.515,and 21 haplotypes could be divided into two groups,one in Yunnan Plateau and the other in Guizhou Plateau.The historical dynamic analysis showed that I.yunguiensis had experienced rapid expansion in history.The coefficient of genetic differentiation between populations was Gst = 0.183,Nst = 0.344,and the structure of variation was not significant(P > 0.05),indicating that there is no obvious genealogical structure of I.yunguiensis in its existing distribution area.(4)The simulation of potential distribution area shows that the most suitable distribution area of I.yunguiensis is in the middle and west of Guizhou Plateau and the east of Yunnan Plateau;the last interglacial period is significantly smaller than the current one;the last interglacial period increased the distribution range of Yunnan,and the distribution range of Guizhou decreased,but the distribution range of the most suitable region is larger and more complete;in the future,it is the same with the current distribution area basically.Combined with field investigation and molecular genetic data,the current conservation strategy is to divide at least two regions in Guizhou Plateau and Yunnan Plateau in situ,focusing on protecting populations with high genetic diversity or haplotype diversity and populations with stable haplotypes.