毛乌素沙地柠条群体分子生态学初步研究:RAPD证据

PRIMARY STUDIES ON MOLECULAR ECOLOGY OF Caragana spp.POPULATIONS DISTRIBUTED OVER MAOWUSU SANDY GRASSLAND:FROM RAPD DATA

毛乌素沙地柠条群体是一个杂种带。为了进一步阐明分子变异和基因流与生境或生态过渡带的联系，应用ＲＡＰＤ标记开展了柠条群体的分子生态学研究。根据ＲＡＰＤ数据利用Ｓｈａｎｎｏｎ信息指数估计了６个柠条群体的遗传多样性，发现大部分的分子变异存在于柠条群体之内（８２．４％），只有少部分的分子变异存在于群体之间（１７．６％）。又利用Ｎｅｉ指数统计了ＲＡＰＤ数据，也证实了大部分的遗传变异存在于群体之内。柠条锦鸡儿群体与中间锦鸡儿群体的遗传分化系数和遗传距离都很小。以上结果都肯定了柠条群体间和种间的基因流动。无论是从多态位点比率还是群体的遗传多样性来看，硬梁和硬梁覆沙群体是最小的，滩地覆沙群体则具有较高的水平。某些ＲＡＰＤ扩增片段的频率在柠条群体间有规律的变化也许具有着特殊的生态学意义，更可能是中性突变的随机固定。根据以上研究可以得出下列结论：①通过比较Ｓｈａｎｎｏｎ指数和Ｎｅｉ指数的统计结果，可以认为，对于异交植物来讲，Ｓｈａｎｎｏｎ指数在统计ＲＡＰＤ数据方面有用。②毛乌素沙地柠条群体之间存在着强大的基因流。

To reveal the relationship between molecular variation,gene flow and the habitats,RAPD markers were used to study the molecular ecology of Caragana spp.populations in Maowusu sandy grassland.Estimated by Shannon phenotypic diversity index from RAPD data,it was found that 82 4% of molecular variation existed within the populations while 17 6% of which among populations.The genetic different coefficient and genetic distance between populations of C.korshinskii and of C.intermedia were small that gene flow between two species was confirmed.In the terms of the proportion of polymorphic loci and genetic diversity of populations,the population of hard ridge(PHR)and that on hard ridge with sand covered(PHRS)had the lowest level,while the population on lowland with sand covered(PLS)had the highest level.Freguecies of some amplified fragments regularly varied among populations especially between PHR、PHRS and PLS,which might have special sense in ecology,most likely,resulted from random fixation of neutral mutation.It could be concluded that:1)Shannon phenotypic diversity index was useful in statistics of RAPD data for outbreeding plants,compared with Nei's index.2)Strong gene flows existed among Caragana spp.populations in Maowusu sandy grassland.The hybrid zone was consistent with the ecotone.