Outcrossing Rates and Gene Flow in Natural Population of the Endangered Endemic Aquatic Lycophyte Isoetes yunguiensis as Revealed by ISSR Markers

Abstract

In this study, mating system, genetic diversity, and genetic structure of the endangered endemic aquatic Isoetes yunguiensis in China was investigated using ISSR markers. The results of ISSR analyses showed that the estimate of multilocus outcrossing rate (tm) was high at species level (tm = 0.955), indicating that diploid I. yunguiensis is a predominant outcrossing species. Nine selected ISSR primers used in the study amplified 66 reproducible bands, 41 of which were polymorphic among 37 individuals. High level of genetic diversity was detected at the species level (PPB = 62.12%), whereas, relatively low genetic diversity existed within populations (PPB = 39.39%). Analysis of molecular variance (AMOVA) revealed that 31.99% of the genetic variation was attributable to differences between populations and the rest (68.01%) to variability within populationsof I. yunguiensis. Value of Fst (0.320) indicated that genetic differentiation between populations also was significant. These results showed that I. yunguiensis predominantly favors crossing, and has a high level of genetic diversity and highly significant genetic variation between and within populations. Gene flow (Nm) among populations is equal to 1.177. High outcrossing rates may be responsible for the high levels of genetic diversity observed in the I. yunguiensis population. To maintain the current level of genetic diversity for this species, we recommend increasing in situ conservation sites.

Phylogeography of the rare and endangered lycophyteIsoetes yunguiensis

“…Most rare and endangered plants are seed plants that can achieve a higher gene flow via long-distance pollen and seed dispersal than ferns that rely solely on spores. Ma et al (2018) investigated the genetic structure of I. yunguiensis using inter-SSR markers and showed inter-and intrapopulation genetic variations of 31.99% and 68.01%, respectively. Similarly, Dong et al (2018) used amplified fragment length polymorphism markers and showed inter-and intrapopulation variations of 40.12% and 59.88%, respectively.…”

“…In particular, I. yunguiensis megaspores are protuberant and numerous compared with I. japonica megaspores, and both species have a distinct number of chromosomes (2n = 22 in I. yunguiensis vs. 2n = 66, 67, 77, 88, or 89 in I. japonica). Recent studies on I. yunguiensis have mainly focused on its morphology (Zhao, Yan & Liu, 2015), palynology (Liu et al, 2013), and molecular genetics (Ma et al, 2018;Dong et al, 2018). However, to the best of our knowledge, no studies on its evolution and biogeography have been published.…”

Peer Review #1 of "Phylogeography of the rare and endangered lycophyte Isoetes yunguiensis (v0.2)"

“…yunguiensis vs. 2n = 66, 67, 77, 88, or 89 in I. japonica). Recent studies on I. yunguiensis have mainly focused on its morphology (Zhao et al, 2015), palynology (Liu et al, 2013), and molecular genetics (Ma et al, 2018;Dong et al, 2018). However, to the best of our knowledge, no studies on its evolution and biogeography have been published.…”

Figure 2: Dendrogram obtained from the dissimilarity matrix based on the Nei genetic distances using an unweighted pair-group method of cluster analysis that used arithmetic averages (UPGMA).

“…These plants have mature spores before the reduction of soil humidity, and it is possible that this is the moment in which spores were dispersed, as reported by Taylor & Hickey (1992). For an amphibious plant, spore dispersion is more complicated and limited by the rainy season and other factors, such as wind (Troia, 2016;Ma et al, 2019).…”