中文摘要：

采用issrt（Inter—simple sequencerepeat）分子标记对内蒙古半日花（Helianthemum ordosicum）自然居群的遗传多样性和遗传结构进行了分析。20个多态性引物在4个居群（412个体）中共检测到246条带（211条具多态性），多态位点比率为86．3％。在居群水平上，Nei’s基因多样性和Shannon’s信息指数分别为0．247和0．318；在物种水平上分别为0．306和0．461。基因分化系数Gst为0．432，基因流Nm值为0．658。分子方差（AMOVA）分析显示总的遗传变异中有46．67％的遗传变异存在于居群间。居群间聚类分析表明：千里沟与桌子山居群遗传距离最小，其次为与棋盘井居群，最远为与阿尔巴斯居群，Mantel检测表明半日花遗传距离与地理距离无相关性。本研究结果表明半日花居群间和居群内具有较丰富的遗传多样性，为今后有效保护半日花种质资源提供了理论依据。

英文摘要：

The genetic diversity and population structure of 4 （Helianthemum ordosicum） populations we analyzed in west Ordos na- tional nature reserve of Inner Mongolia using the ISSR markers. The results were as follows ： Twenty Polymorphic ISSR primers ampli- fied 246 DNA fragments, of which 211 （86.3%） showed polymorphisms among the populations. The percentage of polymorphic bands at the population level was 83.1%. Nei＇ s and Shannon＇ s information index were 0.247 and0. 318, respectively, at the population level, both index were 0.306 and 0.461, respectively, at the species level. Moreover, the Analysis of Molecular Variance （AMOVA） showed that 46.67% of the total genetic diversity was among populations. Relatively lower gene flow （ Nm = 0. 658） might be one of important factors influencing the genetic structure of the species. Based on the genetic distance, Neighbor - joining cluster analysis shows that the Mt. Zhuozi and Qianligou populations grouped together firstly, and then clustered with Qipanjing populations, which were clustered finally with Aerbasi population, Mantel test showed that there was no correlation between genetic and geographic dis- tances. The present analysis reveals that H. ordosicum has high genetic diversity and high genetic differentiation, and provides a theo- retical basis for the future effective protection of H. ordosicum germplasm.