4个群体文蛤的RAPD分析

RAPD analysis of four populations of clam Meretrix meretrix

用建立的高重复性RAPD优化体系，对文蛤Meretrix meretrix4个不同地理群体（广西文蛤Gh、白壳文蛤Gb、山东文蛤S、江苏文蛤J）的个体进行RAPD分析，获得了较好的重复性条带。从20个随机引物中筛选出6个引物进行RAPD扩增，结果显示：Gb群体有11条特征带，Gh群体有2条，这些特征性RAPD扩增带可以作为这两个群体的RAPD分子标记；J群体和S群体没有明显特征带，可能预示这两个群体间遗传渐渗导致种质资源趋向同质化；Gh、S、J群体多态比例差别不大，为61．54％-62．86％，而Gb群体仅为33．33％。采用修正后的Shannon多态性指数方程进行遗传多态性分析，结果显示：Gh、S、J群体多态性指数分别为0．189、0．195、0．200、Gb群体仅为0．115。研究结果表明，文蛤不同群体的遗传地理分化明显，Gh、S、J群体遗传多样性水平较高，而Gb群体的遗传多样性较低，可能预示该群体分布范围较小、群体数量不大，应加强对其资源的保护。Gh与Gb群体为同一栖息地，除壳色和壳形态差异外，遗传多态性差距悬殊，已超出种内变异范围，二者是否为不同种或具生殖隔离的地理亚种，还待于深入研究。

DNA samples of four populations （ Gh, Gb, S, J） of clam Meretrix meretrix were analyzed using an optimized RAPD system with high reproducibility. Six primers were amplified bands from 20 primers. The results showed that Gb population had 11 specific bands, and the Gh 2 specific bands, which acted as molecular markers of distinguishing the different populations. The J and S populations had no specific bands. The Gb population had polymorphic locus proportion of 33.33% , and the others had the proportion from 61.54% to 62.86%. The Shannon＇s index of phenotypic diversity （H） of the Gb was 0. 115, and the others from 0. 189 to 0. 200. The results showed that Gh, J, and S populations had high genetic diversity, surely belonging to Meretrix rneretrix, but the Gb low, indicating that the Gb would be a small population, an independent species or subspecies. Whether Gb group belongs to Meretrix lusoria, Meretrix larmarckii, or even a new species of genus Meretrix needs further research.