准噶尔无叶豆片断化居群的遗传变异及克隆多样性

准噶尔无叶豆(Eremosparton songoricum)是豆科无叶豆属小半灌木, 既能开花结实进行有性繁殖, 又可以靠根茎进行无性克隆繁殖, 为国家三级保护植物, 在中国仅片断化分布于新疆古尔班通古特沙漠局部区域。本文采用ISSR分子标记对采自古尔班通古特沙漠腹地及边缘的7个准噶尔无叶豆自然居群共148个个体进行了遗传变异和克隆多样性分析。8个引物共扩增出84个位点, 其中77个为多态性位点, 物种水平上的多态位点百分比PPB为91.67％, Nei's基因多样性指数I为0.3192, Shannon信息指数H为0.3540; 居群水平上的多态位点百分比PPB为58.45％, Nei's基因多样性指数I为0.2248, Shannon信息指数H为0.3270。居群间的遗传分化系数G_ST为0.2978。AMOVA分析表明, 有31.88%的遗传变异存在于居群间, 表明居群间存在显著的遗传分化。克隆多样性分析表明, 居群水平上, 居群G的Simpson多样性指数和均匀度指数最高, 分别为0.9400和0.9885; 居群E最低, 分别为0.8457和0.9021。物种水平上, Simpson多样性指数为0.9858, 均匀度指数为0.9673。本研究结果表明, 和其他荒漠植物相比, 准噶尔无叶豆表现出较高的遗传变异水平和克隆多样性, 这主要与该物种兼性生殖的繁育方式及多克隆起源有关; 而居群间产生了显著的遗传分化则主要由于人为干扰引起的生境片断化和居群减小而导致的基因交流障碍所致。遗传变异水平和遗传结构的研究将为分析准噶尔无叶豆致濒原因及进化潜力提供重要资料, 对该物种保护具有指导意义。

Genetic variation and clonal diversity in fragmented populations of the desert plant Eremosparton songoricum based on ISSR markers

Eremosparton songoricum is a clonal shrub that reproduces both asexually by below-ground rhi-zomes and sexually by seeds.Having been severely disturbed by human activities,it has greatly declined in range,population number and population size over the past decades.It is now a rare species with a narrow distribution in fragmented habitat patches in the Gurbantuggut Desert of Xinjiang,China.Inter-Simple se-quence repeats(ISSR) were used to evaluate the genetic variation and clonal diversity of seven populations(148 individuals) of E.songoricum from Gurbantunggut Desert.A total of 84 discernible bands were gener-ated using eight primers of which 77 were polymorphic,indicating considerable genetic variation at the spe-cies level(PPB=91.67%,I=0.3192) and at population level(PPB =58.45%,I=0.2248) compared to other de-sert plants.A relatively high value of GST(0.2978) indicated significant genetic differentiation among popu-lations.Analysis of molecular variance(AMOVA) revealed that 31.88% of the ISSR variation resided among populations.Barriers of gene flow caused by habitat fragmentation and population size reduction may contribute to the significant genetic differentiation among populations.Simpson diversity index(D) ranged from 0.8457-0.9400 at population level,indicating that clonal diversity was also high.The evenness of dis-tribution of genotypes in the seven populations was 0.9673 at species level,with all of the genotypes being local ones.The high level of genetic variation and clonal diversity found in E.songoricum are probably due to outcrossing or mixed-mating breeding system and multi-clone origin of populations.The results provide baseline data for formulating conservation strategies for this species.Conservation strategies should include both in situ and ex situ approaches to preserve the greatest possible extent of the genetic diversity of the species.