中国桫椤科植物叶绿体trnL内含子和trnL-trnF基因间隔区序列的系统发育分析

Phylogenetic Analysis of the Chloroplast trnL Intron and trnL-trnF Intergenic Spacer Sequences of the Cyatheaceae Plants from China

摘要:

运用对PCR产物直接测序和克隆后测序的方法测定了蚌壳蕨科1种和桫椤科11种(其中桫椤分别测定19株,小羽桫椤测定2株)植物的叶绿体trnL基因内含子和trnL-trnF基因间隔区序列。12种植物相应的长度介于1 004-1 082之间,A+T平均含量60.9%,G+C平均含量39.1%。计算了不同种间以及种内不同个体间序列的碱基差别(转换值/颠换值)和Kimura遗传距离。序列数据经排列后分别进行最简约法、最大似然法和邻接法分析,结果显示:(1)白桫椤、海南白桫椤和大羽桫椤构成的分支最早和该科内其余植物组成的另一分支分歧,而后者又进一步分为两个亚分支,分别和桫椤亚属、黑桫椤亚属对应,支持夏群的分类处理；(2)大桫椤—狭羽桫椤—毛轴桫椤—篦齿桫椤、大羽桫椤—白桫椤—海南白桫椤以及小羽桫椤—桫椤各自构成独立、自然的末端分支,再参照分支内植物间的遗传距离取值,建议将此3个末端分支依次归并为3种:大桫椤、白桫椤和桫椤；(3)白桫椤属在科内处于基部位置,桫椤属的桫椤亚属和黑桫椤亚属为衍生分支,赞同Tryon关于桫椤科进化和囊群盖起源的假说。

Abstract:

The chloroplast trnL intron and trnL-trnF intergenic spacer (IGS) sequences of one species in Dicksoniaceae (Cibotium barometz) and 11 species in Cyatheaceae were determined by sequencing cloned PCR products or amplified fragments directly (for Alsophila spinulosa and Cyathea tsangii, 9 and 2 individuals were sequenced, respectively). Sizes of the sequences of the 12 species ranged between 1004 bp to 1082 bp. The average contents of (A+T)% and (G+C)% were 60.9% and 39.1%, respectively. The base differences (transition/transversion) and Kimura's genetic distances were also computed between different species and intraspecific individuals. After sequence alignment, maximum parsimony, maximum likelihood and neighbor-joining methods were used to conduct phylogenetic analyses. The results indicated that Xia's classification of Chinese Cyatheaceae was supported, the dade consisting of Sphaeropteris brunoniana, Sphaeropteris hainanensis and Cyathea contaminans firstly diverged from the rest members of the family, and the latter was further separated into two subclades corresponding to the subgenus Alsophila and subgenus Gymnosphaera. Three monophyletic terminal clades, within each the pairwise genetic distances were less than 0.008, were formed separately by Cyathea gigantean-C. pseudogigantea-C. tinganensis-C. pectinata, C. contaminans-Sphaeropteris brunoniana-S. hainanensis, and Cyathea tsangii-Alsophia spinulosa, suggesting that these species could be combined as three separate species: Cyathea gigantean, Sepaeropteris brunoniana and Alsophila spinulosa. The genus Sphaeropteris was placed in the basal position of Cyatheaceae, whereas the genus Alsophila placed as the derived sister group, which supported Tryon's hypothesis accounting for the evolutionary relationships within Cyatheaceae and the derivation of their indusium.