基于核微卫星的短柄枹栎居群遗传多样性和遗传结构

摘要

[Objective]Quercus serrata var. brevipetiolata as one of the important forest tree species in south China has degenerated due to recent human influences. Study of genetic diversity and genetic structure,as well as correlation between genetic structure and geographical distributions can help to develop sound conservation strategies for Q. serrata var. brevipetiolata. [Method]In this study,a total of 398 individuals of 24 Q. serrata var. brevipetiolata natural populations across the species distribution were collected. Eight nuclear microsatellite ( nSSR ) markers with rich polymorphism were used to analyze the genetic diversity of each population,and genetic differentiation was estimated with analysis of molecular variance ( AMOVA) . Genetic structure at species level and correlation between genetic structure and geographical elements of Q. serrata var. brevipetiolata were evaluated using STRUCTURE and Alleles In Space programs.[Result]Results indicated rich genetic diversity of the species ( He =0. 43,Ho =0. 28,Na =3. 67,Ne =1. 96,I =0. 66,PPL =82. 81%). Analysis of molecular variance (AMOVA) showed that genetic variation mainly existed within populations (FST = 0. 22,P < 0. 001),and the genetic diversity differed among different populations. Two groups containing the east and the west populations were plotted based on the Bayesian clustering analysis( STRUCTURE) ,and gene flow existed among these populations ( Nm =1. 88 ) . Great genetic differentiation existed between the two groups containing the east and west geographical populations of the species (FST = 0.25,P < 0.001),while the genetic variations was relatively low among the populations of each group. The Landscape Shape Interpolation analysis ( AIS) also suggested great genetic differentiation between the east and west populations,which was consistent with the STRUCTURE cluster results. No correlation was found between the genetic distance and geographical distance ( R2 = 0. 011,P =0. 07).[Conclusion]The genetic diversity analysis revealed rich genetic diversity of Q. serrata var. brevipetiolata based on the nSSR markers,which was related to its complex population dynamics,anemophilous characteristics and its habitat conditions. Great genetic differentiations exised between the east and west populations,and high differentiations were also found among the west populations. The genetic structure of Q. serrata var. brevipetiolata was probably accounted for the heterogeneity of species habitats ( i. e. ,the western areas with more mountains; the relatively low elevations of east areas with flat terrain; the geographical isolation caused by the smooth topography in the central region ) and fragmented environments caused by current human influences. Overall,our study revealed the genetic diversity and genetic structure of Q. serrata var. brevipetiolata,providing a theoretical basis for developing effective conservation strategies for this species.%【目的】短柄枹栎作为中国南方重要的森林树种之一，近年来受人为活动影响物种退缩严重，对该物种居群的遗传多样性、遗传结构以及遗传结构与地理分布的相关性进行研究，以对短柄枹栎提出相关的保护策略。【方法】共采集到24个短柄枹栎居群共计398个个体，样本覆盖短柄枹栎现今的分布范围。采用8对变异丰富的核微卫星(nSSR)分子标记统计短柄枹栎各个居群的遗传多样性，使用分子方差分析(AMOVA)计算物种的遗传差异，并采用 STRUCTURE和 Alleles In Space软件分析物种整体的遗传结构，探讨短柄枹栎遗传结构与其地理环境的关系。【结果】短柄枹栎居群具有丰富的遗传多样性，平均期望杂合度 He =0.43，平均观测杂合度 Ho =0.28，平均等位基因数 Na =3.67，平均有效等位基因数 Ne =1.96，平均 Shannon 指数 I =0.66，多态位点百分率 PPL =82.81%；短柄枹栎的遗传差异主要存在于居群内部(FST =0.22，P ＜0.001)，不同居群的遗传多样性存在差异。基于贝叶斯的聚类分析( STRUCTURE)将短柄枹栎居群划分为东部和西部2组，居群之间存在基因交流( Nm =1.88)。东部群组和西部群组之间存在较大的遗传分化(FST =0.25，P ＜0.001)，而东、西群组内部居群之间的遗传差异则相对较小。居群景观遗传分析( AIS)显示东部与西部群组之间较大的遗传差异，这一结果与聚类分析(STRUCTURE)的结果一致；居群间遗传距离和地理距离没有显著的相关性(R2=0.011，P =0.07)。【结论】基于核 SSR标记的遗传多样性研究显示短柄枹栎具有丰富的遗传多样性，这一特性与其复杂的种群动态历史、风媒传粉的生物学特性及所处的生活环境相关，短柄枹栎东部和西部分布的居群之间存在较大的遗传分化，西部居群之间也有较大的遗传差异。短柄枹栎现今的遗传结构可能源于该物种自然生境的异质性(如：西部地区山脉较多；东部地区海拔较低，地势较为平缓；中部地区平缓的地势所产生的地理隔离)以及近期人类活动引起的生境片段化。本研究从整体水平上揭示了短柄枹栎的遗传多样性及遗传结构特征，为该物种的遗传保护提供理论依据。