中国穗状狐尾藻遗传多样性的初步分析

利用叶绿体DNA三个片段(trnK-matK、trnL-trnF、rpl32-trnL)对中国大陆广布的水生植物穗状狐尾藻(Myriophyllum spicatum L.)的遗传多样性进行了初步分析,以探讨其自然居群的遗传结构及具有广泛分布格局的可能机制。AMOVA分析显示,穗状狐尾藻8个居群间的遗传变异为84.97%,而居群内的遗传变异为15.03%,居群遗传分化系数(Fst)为0.85,表明穗状狐尾藻具有较高的遗传多样性(Hd=0.83)且主要存在于居群间,奠基者效应可能导致了最初的遗传差异,而隔离障碍(Nm=0.09)又进一步导致了居群间的遗传分化。基于17个单倍型构建的系统发育树和网络关系图均显示,单倍型H5和H6在居群中的分布范围最广且出现频率最高,表明H5和H6可能为最古老的祖先单倍型。Mantel检验表明居群间的遗传距离与地理距离之间不存在显著的相关性,失配分布检测结果显示穗状狐尾藻在历史上曾发生过扩张事件,而Tajima’s、FuLi’s D*和F*检测发现,该物种不存在明显的谱系地理格局,这可能与穗状狐尾藻种子的长距离扩散有关。

Preliminary Analysis on the Genetic Diversity of Myriophyllum spicatum from China

To determine the genetic structure of natural Myriophyllum spicatum populations in mainland China and the possible mechanism that led to the widely distributed pattern of the species, eight populations were examined for preliminary genetic analysis based on three chloroplast DNA segments (trnK-matK, trnL-trnF, rpl32-trnL). The AMOVA analysis results showed that the genetic diversity among the eight populations was 84.97% and within the populations was 15.03%. Furthermore, the population genetic differentiation coefficient (Fst) was 0.85, indicating high genetic diversity in M. spicatum (Hd=0.83) among populations. The founder effect may have led to the initial genetic differences and segregation barriers (Nm=0.09) may have further resulted in genetic differentiation among populations. From the constructed phylogenetic tree and haplotype network based on 17 haplotypes, haplotypes H5 and H6 had the highest frequency and widest distribution, indicating they were possibly the oldest ancestral haplotypes. The Mantel test showed no significant correlation between genetic and geographic distances among populations, and the mismatch distribution test showed that historic M. spicatum populations likely experienced expansion events. Tajima's, Fu & Li's D^* and F^* tests showed that this species did not have an obvious phylogeographic pattern, which may have resulted from long distance dispersal of seeds.