小果油茶与普通油茶居群遗传结构及种间杂交渐渗

Population genetic structure and interspecific introgressive hybridization between Camellia meiocarpa and C. oleifera

利用11对SSR引物对5个同域分布的小果油茶和普通油茶居群进行了遗传多样性、居群遗传结构,以及种间杂交渐渗的研究.结果表明:两物种的共有等位基因数为57个,占总数的96.6%;在普通油茶中仅检测到2个特异等位基因,而在小果油茶中没有检测到特异等位基因,但两物种的等位基因频率存在一定的差别.两物种的遗传多样性均较高.在物种和居群层次上,两物种的多态信息含量的变化幅度均为0.25～0.50,属于中度多态性.同域分布的两物种间的平均遗传分化系数为0.057,明显低于物种内异域居群间的遗传分化系数的平均值(小果油茶0.332,普通油茶0.201),也低于木本被子植物种内居群间平均水平(0.102).5个同域分布物种间基因流的平均值为10.072,明显高于物种内异域间基因流的平均值(小果油茶1.006,普通油茶1.990).UPGMA聚类结果显示,小果油茶和普通油茶之间的亲缘关系非常接近,明显存在着因杂交而产生的基因渐渗.小果油茶或许是普通油茶的一个变种.

A total of 11 pairs of SSR primers were applied to study the genetic diversity of five sympatric populations of Camellia meiocarpa and C. oleifera, the populations’ genetic structure, and the interspecific introgressive hybridization. The alleles shared by the two species were 57, accounting for 96.6% of the total. There were two specific alleles in C. oleifera, but no specific alleles in C. meiocarpa. Certain difference was observed in the phenotypic frequency between the two species, and the intraspecific genetic diversity of the two species was high. At species level and population level, the polymorphism information content of the two species was between 0.25 and 0.50, suggesting that the genetic polymorphism was moderate. The mean value of genetic differentiation among the sympatric species was 0.057, being obviously lower than that of the foreign species （C. meiocarpa 0.332; C. oleifera 0.201） and of xyloid angiosperms （0.102）. The mean value of gene flow among the sympatric species was 10.072, which was significantly higher than that among the foreign species （C. meiocarpa 1.006, C. oleifera 1.990）. The UPGMA cluster results showed that the genetic relationship of the two species was very close to, meaning that there existed an obvious interspecific introgressive hybridization. C. meiocarpa was possibly a variety of C. oleifera as a result of the introgressive hybridization.