Spatial Genetic Structure in Natural Populations of Phragmites australis in a Mosaic of Saline Habitats in the Yellow River Delta, China

Lexuan Gao,Zhu Zhu,Bo Li,Ji Yang,Liqiong Zhuge,Shaoqing Tang,Ming Nie,Giovanni G Vendramin

doi:10.1371/journal.pone.0043334

Abstract

Determination of spatial genetic structure (SGS) in natural populations is important for both theoretical aspects of evolutionary genetics and their application in species conservation and ecological restoration. In this study, we examined genetic diversity within and among the natural populations of a cosmopolitan grass Phragmites australis (common reed) in the Yellow River Delta (YRD), China, where a mosaic of habitat patches varying in soil salinity was detected. We demonstrated that, despite their close geographic proximity, the common reed populations in the YRD significantly diverged at six microsatellite loci, exhibiting a strong association of genetic variation with habitat heterogeneity. Genetic distances among populations were best explained as a function of environmental difference, rather than geographical distance. Although the level of genetic divergence among populations was relatively low (F’ST = 0.073), weak but significant genetic differentiation, as well as the concordance between ecological and genetic landscapes, suggests spatial structuring of genotypes in relation to patchy habitats. These findings not only provided insights into the population dynamics of common reed in changing environments, but also demonstrated the feasibility of using habitat patches in a mosaic landscape as test systems to identify appropriate genetic sources for ecological restoration.

Highlights

Spatial configuration of suitable environments for organisms is often patchily structured at various scales, from biogeographic regions to local environments within a landscape [1,2,3,4]
We aimed to address the feasibility of using patchy habitats as test systems to evaluate the potential for plants to adapt dynamically to changing environments, which is vitally important for selecting appropriate plant materials for ecological restoration [52]
We calculated the frequencies of heterozygous and homozygous individuals with these alleles in different populations, and found a significant positive correlation between the 203(PaGT9) frequency and the soil salinity of sampling sites, with the frequency of the 203(PaGT9) homozygote increasing from 3.4% for the lowest saline population (YJNH) to 69.0% for the highest saline population (YJ124) (R2 = 0.387, P,0.001) (Fig. 4). Despite their close geographic proximity, the common reed populations in the Yellow River Delta (YRD) significantly diverged in overall genetic diversity within population, and in allele frequencies at six microsatellite loci

Summary

Introduction

Spatial configuration of suitable environments for organisms is often patchily structured at various scales, from biogeographic regions to local environments within a landscape [1,2,3,4]. The population structure and dynamics of species in patchy environments depend on the spatial arrangement and heterogeneity of habitats [2,8,9,10,11,12,13,14,15]. Numerous studies have revealed the role of environmental patchiness in generating spatial genetic structure (SGS) in natural populations [10,16,17,18,19,20,21,22,23]. SGS, i.e. nonrandom spatial distribution of genotypes and alleles, can result from different processes, including restricted gene dispersal, genetic drift, and micro-environmental selection [22,24,25]. Understanding the processes underlying population structure and its relationships with habitat structure and heterogeneity can help reveal the potential driving forces promoting population divergence and adaptation, but may contribute to the prediction of how populations will respond to changing environments, which is important for both conservation and restoration efforts

Methods

Results

Conclusion