Phylogeography of the rare and endangered lycophyteIsoetes yunguiensis

Background Isoetes yunguiensis Q. F. Wang & W. C. Taylor is a lycophyte of an ancient genus, and it is endemic to China. It is a first-class protected plant in China. This living fossil is used in paleoecology and studies on the evolution of Lycophytes in the Yunnan-Guizhou Plateau. In recent years, human activities have caused the disappearance of several wild populations, and the number of plants in the existing populations is low. Study of the genetic structure, distribution pattern, and historical dynamics of I . yunguiensis in all areas of its distribution is of guiding significance for its rational and effective protection. Methods Expressed sequence tag-simple sequence repeat (EST-SSR) markers were used to study the genetic diversity and structure of I . yunguiensis , and noncoding chloroplast DNA (cpDNA) sequences were used to study the pedigree, population dynamics history, and glacial shelter of I. yunguiensis . A maximum entropy model was used to predict the past, present, and future distribution patterns of I. yunguiensis . Results Analysis with EST-SSR markers revealed that I. yunguiensis showed high genetic diversity and that genetic variation was significantly higher within populations than between populations. Based on cpDNA data, it was concluded that there was no significant geographic pedigree in the whole area of I. yunguiensis distribution (NST = 0.344 >  GST = 0.183, p  > 0.05); 21 haplotypes were detected using DnaSP v5. Neutral test and LAMARC simulation showed that I. yunguiensis has experienced rapid expansion in recent years. The maximum entropy model predicted that the potential distribution area of I. yunguiensis in the last glacial maximum period has increased significantly compared with the present distribution area, but the future distribution area did not show substantial changes.