荷叶铁线蕨自然居群的遗传多样性研究

荷叶铁线蕨(Adiantumreniformevar. sinense)为我国特有植物,具有重要的经济价值,目前仅分布于重庆的少数地区。近几十年来,由于过度开发,该种的分布范围日益缩小,已处于灭绝的边缘。本研究利用等位酶标记检测了荷叶铁线蕨 6个自然居群共 136个个体的遗传多样性,共检测到了 5个酶系统的 14个位点,获得了 7个多态位点。结果表明:与其他蕨类植物相比,荷叶铁线蕨居群内的遗传多样性水平比较低。平均每位点的有效等位基因数(Ae)为 1. 778,多态位点百分率(P)为 0. 441,期望杂合度(He)为 0. 199,观察杂合度 (Ho)为 0. 235。其居群间的遗传分化也很低,居群间的遗传变异仅占总变异的 1. 49%,而 98. 51%的变异存在于居群内部。采用Hardy Wein berg平衡和固定指数F对荷叶铁线蕨的居群遗传结构进行了分析,结果表明其种群可能是以配子体间异交为主的混合交配体系。导致荷叶铁线蕨濒危的主要原因是生境的破坏以及过度开采所导致的生境片断化使其居群变小、近交率加大、遗传变异趋低,降低了其生存以及进化的潜力。

Genetic diversity of the natural populations of Adiantum reniforme var. sinense

Adiantum reniforme var. sinense is an economically important plant species endemic to China. It is only found in a few regions of the Chongqing Municipal Region. For decades, its distribution has been shrinking as a result of over exploitation, which has caused endangerment of this species. To assist in efforts to effectively conserve this species, we investigated the genetic variation of six natural populations using isoelectric focusing in thin layer polyacrylamide slab gels. Fourteen loci of five enzyme systems were detected, of which seven were polymorphic. The mean number of effective alleles per locus ( A e ) = 1.778, the percentage of polymorphic loci ( P ) = 0.441, the mean expected heterozygosity ( H e )= 0.199, and the mean observed heterozygosity ( H o )= 0.235. The results revealed that low levels of genetic diversity existed within the natural populations of A. reniforme var. sinense in comparison with other species of ferns. Only 1.49% of the genetic variation occurred among populations whereas 98.51% existed within populations, suggesting a very low genetic divergence among the populations. The equilibrium state of the populations was measured using Hardy Weinberg equilibrium and the Fixation Index ( F ). The results showed that a mixed mating system was possibly the main heterogamy of this species, and its endangerment was caused by over exploitation and habitat loss.