THE APPLICATION OF SEQUENCE ANALYSIS OF rDNA FRAGMENT TO THE SYSTEMATIC STUDY OF THE SUBFAMILY CYRTANDROIDEAE(GESNERIACEAE)
WANG Xiao Quan LI Zhen Yu (Laboratory of Systematic and Evolutionary Botany,Institute of Botany,the Chinese Academy of Sciences,Beijing 100093)
A molecular phylogeny of the subfamily Cyrtandroideae represented by five genera of four tribes was constructed using sequence analysis of the internal transcribed spacers (ITS) and partial 5.8 S rRNA gene (3′end) of nuclear ribosomal DNA. Direct PCR sequencing method was used in the study. The sequences of ITS 1 in the five species range from 234 bp to 258 bp in size and those of ITS 2 from 218 bp to 246 bp. The ITS 1 (258 bp) and ITS 2 (218 bp) of Whytockia bijieensis differ greatly from those of the other species in size, sequence and G+C content, and therefore the tribe Klugieae represented by W. bijieensis may have diverged from the ancestor of the subfamily Cyrtandroideae at a very early time. In PAUP analysis, W. bijieensis was used as the functional outgroup, and only one most parsimonious Fitch tree was obtained through exhaustive search. The tree has 353 steps, with CI=0.932 and RI=0.529. In the tree, Chirita crassifolia is basal to a monophyletic group comprising Cyrtandra umbellifera, Briggisia longipes and Anna mollifolia, and the monophyletic group is strongly supported by the bootstrap value (97). The tribes Trichosporeae and Cyrtandreae represented respectively by Anna mollifolia and Cyrtandra umbellifera both evolved from the tribe Didymorcarpeae, which can explain why many intermediate taxa exist among the three tribes. According to this, the present authors suggest that the tribe Trichosporeae and the tribe Cyrtandreae be merged with the tribe Didymocarpeae.