黄河三角洲互花米草的遗传变异和扩散

Genetic Variation and Spread of Spartina alternifora in the Yellow River Delta

互花米草（Spartina alternifora）自1990年被引种到黄河三角洲后,快速扩张,已经威胁了该地区潮间带的生态安全。研究黄河三角洲互花米草群体的遗传变异,拟从遗传进化角度了解其扩散机制,以期为防控和管理互花米草扩张提供科学依据。利用了13对微卫星分子标记,对黄河三角洲4个互花米草群体（群体1~群体4的位置分别在一千二、大汶流、五号桩、黄河口）中共160个个体进行了遗传多样性和遗传结构分析。研究结果表明,黄河三角洲互花米草具有较高的遗传多样性,每个位点平均观察等位基因数（Na）为（7.385±2.256）,平均有效等位基因数（Ne）为（3.636±1.102）,Nei’s基因多样性指数为（0.700±0.094）,Shannon信息指数为（1.453±0.343）,多态位点百分率为100%。群体1的Na、Ne、Nei’s基因多样性指数和Shannon信息指数都最小,而其它3个群体的遗传多样性水平相似。但是,4个群体间存在中等的遗传分化（群体分化率Fst=0.121）,群体间总的基因流也处于中等水平（Nm=1.825）。群体1、群体2和群体3之间的遗传一致度最高,而群体4和其它3个群体间的遗传一致度都比较低。已知群体3是黄河三角洲唯一被引种的互花米草群体,是扩散的源头,根据4个群体的遗传结构,本研究推测互花米草先从群体3扩散到群体4,再从群体3扩散到群体1和群体2,扩散顺序与地理距离不相关,说明互花米草的种子通过海水传播可以实现跳跃式长距离扩散。因此,研制和施用环境友好型药物,使互花米草种子败育,可能是控制互花米草入侵的一种途径。

Spartina alternifora has been introduced into the Yellow River Delta since 1990. It spreads very rapidly and threatens the safety of the ecosystem. Investigating the genetic variation of Spartina alternifora can help understanding the mechanism of invasion and provide basic knowledge for the management of this invasive species. The genetic structure and diversity of four populations of Spartina alternifora （Pop 1, Pop 2, Pop 3 and Pop 4） at 13 loci were analyzed using microsatellite markers. The results revealed that the genetic diversity of Spartina alternifora in the Yellow River Delta was high. The average observed allele number （Na） was 7.385, the effective allele number （Ne） was 3.636, the Nei＇ s genetic diversity was （0.700：L0.094）, the Shannon index was （1.453：L0.343）, and the proportion of polymorphic loci （P） was 100%. The Na, Ne, Nei＇ s genetic diversity and Shannon index of Popl was the lowest, while those of Pop2-Pop4 were similar. However, the genetic differentiation （F,,=0.121） and the gene flow （Nm=1,825） among populations were medium. The genetic similarity among Pop 1-Pop 3 was high while the genetic similarity between Pop 4 and Pop 1-Pop 3 was low. As we known, Pop 3 was the structure of 4 populations suggested that firstly Pop 3 initial and unique introduced population. The genetic dispersed to Pop 4, and then Pop 3 dispersed to Pop 1 and Pop 2. The population dispersal order was not associated with the geographic distance of these populations, for the reason that the seeds of Spartina alternifora could disperse by sea water over a long distance. Therefore, developing environment-friendly herbicide to make Spartina alternifora in fecund could be a good way to control its invasion.