千岛湖陆桥岛屿上黑腹狼蛛(Lycosa coelestris)遗传多样性及其受生境片段化的影响

Genetic diversity of Lycosa coelestris on islands in the Thousand Island Lake(TIL) and the effects of habitat fragmentation

人工湖泊型陆桥岛屿对于理解生境片段化后片段面积和地理隔离等因素对物种遗传多样性和遗传结构的影响提供了独特的机会.本文利用相关序列扩增多态性（SRAP）分子标记法,对具有50多年片段化历史的千岛湖人工湖泊型陆桥岛屿上的黑腹狼蛛（Lycosa coelestris）种群遗传结构和多样性进行研究.利用5对SRAP引物对42份材料的基因组进行扩增,共得到大小为50-900 bp的85个可重复位点,其中84个为多态性位点,多态性比率达98.82%.不同岛屿种群的多态位点比例（PPB）为15.29%-38.82%;观测等位基因数（Na）为1.1529-1.3882,其中有效等位基因数（Ne）为1.0952-1.3392;种群间Nei’s基因多样性指数（H）为0.0582-0.1784,均值为0.0992;Shannon信息指数（I）为0.0881-0.2524,均值为0.1480;岛屿的面积、形状指数分别与多态位点比率、Shannon信息指数以及Nei’s基因多样性指数存在正相关关系.种群间遗传分化系数较高（Gst=0.7293）,基因流值低（Nm=0.1856）.AMOVA分析表明,57.33%的遗传变异存在于种群间,42.67%的遗传变异来自种群内（P〈0.001）.Mantel检验表明,黑腹狼蛛各种群间地理距离与遗传距离间存在显著相关性（r=0.6465,P〈0.001）.采用Structure 2.3.3软件以及PCA分析对14个岛屿上黑腹狼蛛种群的群体结构进行研究,结果表明,所研究岛屿可以分为6个类群,地理距离较近且属同一个岛群的岛屿优先聚在一起.上述结果表明,生境片段化初期岛屿面积和形状是影响黑腹狼蛛种群遗传多样性的主要原因,地理隔离是黑腹狼蛛种群产生遗传分化的主要原因.

Habitat fragmentation caused by human activities poses a serious threat to the genetic diversity of populations. Artificial islands of known age are ideal model systems that offer a unique opportunity to elucidate the consequences of habitat fragmentation and the effects of island area and isolation on genetic diversity and structure of populations. The Thousand Island Lake （TIL） in Zhejiang Province, East China, is a large reservoir that was formed in 1959 by the damming of the Xin＇an River to construct a hydroelectric power station. We used sequence-related amplified polymorphism （SRAP） molecular markers to study the genetic diversity of a species, Lycosa coelestris, with low dispersal ability in the TIL. Five SRAP primer combinations were used to genotype 42 individuals of L. coelestris from 14 islands to estimate its population genetic diversity and structure. The result showed that 5 SRAP primer combinations amplified 85 bands with 84 （98.82%） polymorphism. The percentage of polymorphic bands （PPB） at the population level ranged from 15.29% to 38.82%, the observed number of alleles （Na） from 1.1529 to 1.3882, the effective number of alleles （Ne） from 1.0952 to 1.3392, Nei＇s gene diversity index （H） from 0.0582 to 0.1784 （average 0.0992）, and Shannon＇s information index （/） from 0.0881 to 0.2524 （average 0.1480）. The islands area or shape index had significant correlations with PPB, H, and I. The genetic differentiation coefficient （Gst） among populations was 0.7293 and gene flow （Nm） among populations was 0.1856, which means high genetic differentiation had appeared in the TIL. The analysis of molecular variance showed that the main variance between populations was 57.33% and that within populations was 42.67%. The Mantel test suggested that there was significant association between genetic distance and geographic distance （r=-0.7757, P〈0.01）. The structure and principle components analysis showed that the L. coelestris populations in the TIL can be divided into 6 groups, and populations were geographically closer to one another in each group. These results indicated that island area and shape mainly affect the genetic diversity of L. coelestris populations, and geographic isolation mainly affects genetic differentiation at TIL.