Great influence of geographic isolation on the genetic differentiation of Myriophyllum spicatum under a steep environmental gradient.

Zhigang Wu,Xinwei Xu,Zhong Wang,Dan Yu,Xing Li

doi:10.1038/srep15618

Zhigang Wu, Xinwei Xu + Show 3 more

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https://doi.org/10.1038/srep15618

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Journal: Scientific reports	Publication Date: Oct 23, 2015
Citations: 24	License type: CC BY 4.0

Affiliation: Wuhan University

Abstract

Understanding how natural processes affect population genetic structures is an important issue in evolutionary biology. One effective method is to assess the relative importance of environmental and geographical factors in the genetic structure of populations. In this study, we examined the spatial genetic variation of thirteen Myriophyllum spicatum populations from the Qinghai-Tibetan Plateau (QTP) and adjacent highlands (Yunnan-Guizhou Plateau, YGP) by using microsatellite loci and environmental and geographical factors. Bioclim layers, hydrological properties and elevation were considered as environmental variables and reduced by principal component analysis. The genetic isolation by geographic distance (IBD) was tested by Mantel tests and the relative importance of environmental variables on population genetic differentiation was determined by a partial Mantel test and multiple matrix regression with randomization (MMRR). Two genetic clusters corresponding to the QTP and YGP were identified. Both tests and MMRR revealed a significant and strong correlation between genetic divergence and geographic isolation under the influence of environmental heterogeneity at the overall and finer spatial scales. Our findings suggested the dominant role of geography on the evolution of M. spicatum under a steep environmental gradient in the alpine landscape as a result of dispersal limitation and genetic drift.

Highlights

Location Qinghai-Tibetan Plateau (QTP) Zhongba, Xizang Angren, Xizang Dingri, Xizang Shenzha, Xizang Rikaze, Xizang Cuomai, Xizang Gongbujiangda, Xizang Linzhi, Xizang YGP Yongsheng, Yunnan Dali, Yunnan Chengjiang, Yunnan Leibo, Sichuan Weining, Guizhou
Eurasian watermilfoil is widely distributed in China, and previously, we found that both geographic barriers and climate significantly affected population genetic differentiation across the entire country (Wu et al unpublished)
When the studied M. spicatum populations were divided into two clusters, we found that the eight populations from the QTP were assigned to one cluster and the five populations of the adjacent highlands (YGP) were assigned to another cluster (Figs 1 and 2a)

Summary

Introduction

Location QTP Zhongba, Xizang Angren, Xizang Dingri, Xizang Shenzha, Xizang Rikaze, Xizang Cuomai, Xizang Gongbujiangda, Xizang Linzhi, Xizang YGP Yongsheng, Yunnan Dali, Yunnan Chengjiang, Yunnan Leibo, Sichuan Weining, Guizhou. Eurasian watermilfoil (Myriophyllum spicatum L.) is native to Europe, Asia and northern Africa[15] and is recognized as a noxious weed in North America due to its ability to rapidly spread in new habitats[16]. This species occurs in various types of inland water bodies as it is tolerant to a wide range of water and climatic conditions[17], which may be partly responsible for its cosmopolitan occurrences. Thirteen Eurasian watermilfoil populations were collected in the QTP and adjacent highlands (Yunnan-Guizhou Plateau, YGP) for genetic analysis using microsatellite markers. Our aims were to (1) reveal population genetic structure and gene flow pattern; (2) assess the relative role of geographic isolation and environment heterogeneity in population genetic structure; and (3) find the main force driving genetic divergence of M. spicatum in the alpine environment

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