武陵山区蛇足石杉遗传多样性的AFLP分析

Genetic Diversity of Huperzia serrata(Huperziaceae) in Wuling Mountains Area Detected by AFLP

采用AFLP分子标记对武陵山区蛇足石杉(Huperzia serrata)4个居群进行遗传多样性的研究,结果表明:(1)7对引物组合共扩增出条带615条,其中549条为多态性条带;在物种水平上,多态性条带百分率PPB=89.27%,有效等位基因数Ne=1.257,Nei’s基因多样度指数H=0.178,Shannon多样性信息指数Isp=0.298;在居群水平上,PPB=71.42%,Ne=1.235,H=0.154,Shannon多样性信息指数Ipop=0.251;遗传多样性在居群间有明显的差别,其中坪坝营(PBY)居群最高(PPB=81.95%),而铁峰山(TFS)居群最低(PPB=64.55%)。(2)居群间的遗传分化较低,基于Nei’s基因多样性分析结果显示,居群间遗传分化系数GST=0.159;Shannon’s居群分化系数[(Isp-Ipop)/Isp]为0.16;WINAMOVA分析显示,武陵山区蛇足石杉的遗传变异主要存在于居群内,居群内的遗传变异分量为65.057,占总变异的75.77%,而居群间的遗传变异分量为20.804,占总变异的24.23%;居群内存在极显著的遗传分化(ΦST=0.242,P<0.001)。(3)由遗传分化系数(GST)估计,武陵山区蛇足石杉居群间的基因流Nm=2.647,表明蛇足石杉属于异交种。(4)两两居群间的Nei’s遗传一致度(IN)范围为0.031 0~0.969 4;Mantel检测结果显示,居群间的遗传距离与地理距离之间不存在显著的正相关关系(r=0.269,P=0.887)。研究认为,遗传多样性与遗传结构主要决定于居群历史,较少干扰而稳定的居群偏向克隆生殖,遗传多样性较低,而新建居群的遗传多样性则较高;克隆生长、生态位选择、异交,以及有效的孢子风媒传播等可能是其维持较高遗传多样性水平的因素,而过度采挖等人类活动和生境片断化是导致蛇足石杉濒危的主要因素。

Huperzia serrata,an important traditional Chinese herb, has become a threatened species resulting from over-exploitation and habitat fragmentation in China. We assessed the levels and pattern of the genetic variation within and among four populations of this species in Wuling Mountains area using amplified fragment length polymorphism （AFLP） markers. （1）Seven primer combinations used in the study amplified 615 discernible bands with 549 being polymorphic,indicating a considerable high level of specific genetic diversity （at species level：percentage of polymorphic loci PPB = 89.27 %, effective number of alleles Ne =1. 257, Nei＇s gene diversity H= 0. 178, and Shannon＇ s information index Isp = 0. 298;at population level ： PPB = 71.42 %, Ne = 1.235, H = 0.154, and Shannon＇ s information index /pop = 0.251 ）. The differ- ences among populations in levels of genetic diversity were obvious, with the highest level （PPB = 81.95G） in PBY population and the lowest level （PPB=64. 55%） in TFS population. （2）A low level of genetic differentiation among populations was detected based on Nei＇s genetic diversity analysis （Gsr = 0. 159）,Shannon＇s diversity index （0.16）. Further AMOVA analysis also revealed a low level of genetic differentiation among populations （q^ST = 0. 242, P〈0. 001）. （3） An extraordinarily high level of gene flow （Nm=2. 647） may result from out-breeding and extensive wind-dispersal spores. （4）Nei＇s genetic identity （IN） values between population pairs ranged from 0. 927 9~0. 969 4. A Mantel test showed no significant correlation between genetic distance and geographical distance （r=0. 269, P=0. 887）, suggesting that the gene flow be not restricted geographically. In general,population genetic diversity and genetic structure are mainly determined by population history. The level of the genetic diversity in the less disturbed and stable populations which are dominated by clonal reproduction is lower than those of new young populations which are built by sexual reproduction. A number of factors that might affect the genetic profiles of H. ser- rata include clonal growth,selective effect of niche of spores. and outcrossing,as well as the effective wind-dispersal