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

Mengxue Ma,Kuo Liao,Rui Qin,Xiang Dong,Hong Liu,Fei Hao

doi:10.15835/nbha47111264

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.

Highlights

Plant breeding systems determine gene flow, the genetic structure of populations, and the evolutionary potential of a species (Korpelainen, 1995)
The difference between tm and ts (0.002) in species level was insignificant, suggesting that biparental inbreeding was negligible (Ritland, 1990), indicating that there is a low tendency for Genetic diversity and genetic structure The nine selected primers generated a total of 66 bands
Chen et al (2006) revealed 51.02% inter-simple sequence repeat (ISSR) genetic diversity between populations and within populations of the endangered aquatic fern I. sinensis in China based on ISSR data

Summary

Introduction

Plant breeding systems determine gene flow, the genetic structure of populations, and the evolutionary potential of a species (Korpelainen, 1995). An accurate characterization of mating system is important for the conservation of the evolutionary potential of natural populations because it allows the outlining of strategies that optimize the sampling of genetic variability and the adoption of genetic-statistical models appropriate for the estimation of genetic parameters (Cánovas et al, 2015). Isoetes L., the single remaining member of the family Isoetaceae, is a cosmopolitan genus of heterosporous lycopods comprising 200 or more species, and occupies a very important position in the evolutionary history of the pteridophytes (Hoot et al, 2001). Isoetes yunguiensis is an endangered and endemic aquatic fern in China, and is a basic diploid with a chromosome number 2n = 22 (Wang et al, 2002). I. yunguiensis has declined rapidly in the number and size of populations due to the impact of human activities. Pang et al (2003) reported that five I. yunguiensis populations such as Heilongtan, Songhuaba, Xiaoshao, Shuangshao and Xuandian populations in Kunming City, Yunnan Province

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