基于cpDNA trn L-F 序列数据分析海南陆均松种群的冰期后扩张

针对热带树种陆均松Dacrydium pierrei de Laubenfels分布在海南的12个天然种群进行取样,测定了叶绿体DNA(cpDNA) trn L-F非编码区序列.序列长度介于868～876 bp,显示出长度多态性.碱基组成A T含量较高,百分比值为64.17%～64.95%.通过统计简约算法共鉴定出30个单倍型.根据种群间分化度FST(=0.00)、基因流Nm(介于1.92～2.50)、AMOVA(24.17%的遗传变异发生在种群间,P＞0.05)以及邻接树中单倍型的分支式样,发现海南的陆均松种群尚未发生遗传分化.另一方面,依统计简约算法构建的单倍型网图具"星状"特征,而且邻接树中多数单倍型合并于树的顶端.这些基因谱系结果提示海南陆均松种群在近期历史上发生过种群扩张.Tajima的 D 检验和错配分析结果也支持这种推测.结合地质和古孢粉学证据,认为残存于"避难所"的陆均松种群在全新世时,伴随全球气候转暖,在海南岛内可能实行了扩张.

Postglacial Population Expansion of Dacrydium pierrei (Podocarpaceae) in Hainan, Southern China, Based on cpDNA trn L-F Nocoding Sequence Data

Chloroplast DNA (cpDNA) tmL-F noncoding sequences of individuals of a tropical coniferous species, Dacrydium pierrei, collected from twelve natural populations located in Hainan, southern China, were determined. Sequence length varied from 868 bp to 876bp, showing length polymorphism. Base composition had a high A + T content of 64.17%-64.95%. Thirty haplotypes were identified based on statistical parsimony algorithm. Populations of D. pierrei in Hainan are lack of genetic differentiation. Such a deduction was supported by observed FST values ( = 0.00) , high values for Nm (ranging from 1.92 to 2.50), AMOVA (24.17% of molecular variance attributed to difference among populations, P > 0.05) as well as the branching structure in Neighbour-Joining (NJ) tree constructed from haplotypes. A "star-like" pattern was exhibited in the network of tmL-F haplotypes established by statistical parsimony algorithm, and majority of the haplotypes coalesced near the tips in NJ tree. Gene genealogies of cpDNA haplotypes proposed a recent population expansion of D. pierrei in Hainan, which was further lent support by the results from Tajima's D test and mismatch distribution analysis. Our data in junction with geological and palynological evidences showed that in the Holocene, due to global warming, refuge populations of D. pierrei in Hainan might experience a range expansion.