MOLECULAR PHYLOGENETICS OF THE SUBTRIBE GENTIANINAE (GENTIANACEAE) INFERRED FROM THE SEQUENCES OF INTERNAL TRANSCRIBED SPACERS (ITS) OF NUCLEAR RIBOSOMAL DNA

The internal transcribed spacer (ITS) regions of 18S-25S nuclear ribos omal DNA from representatives of 23 species of the subtribe Gentianina e and one outgroup species (Centaurium capitatum) were analyzed by pol ymerase chain reaction amplification and direct DNA sequencing. Within the taxa analyzed, the length of the ITS1 region varied from 221 to 2 33 bp, ITS2 from 226 to 234 bp. Of the aligned sequences of 497 positi ons, 151 sites involved gaps or nucleotide ambiguity, 133 were invaria ble and 213 showed divergence. In pairwise comparisons among the taxa of the subtribe Gentianinae and the outgroup, sequence divergence rang ed from 1.3% to 34.1% in ITS1, from 0 to 28.1% in ITS2 and from 0.6% t o 27.5% in combined ITS1 and ITS2. Phylogenetic trees generated from I TS sequences were highly resolutive and principally concordant with mo rphological classifications for the major phylogenetic divisions in th e subtribe. An ancient divergence leading to two evolutionary lines wa s suggested in the subtribe by both DNA sequence and morphological dat a. One line encompasses the genera Gentiana, Crawfurdia and Triprerosp ermum, morphologically characterized by their glands on the base of ov ary and their plicate corolla, while the other line involves all other members of the subcribe surveyed, characterized by their epipetalous glands and simple corolla without plicae. Megacodon, with glands on th e base of ovary but without plicae on its corolla, was revealed to be more related to the latter group than to the former. Comastoma, Gentia nella and Gentianopsis were shown to be well-defined monophyletic gene ra. Pterygocalyx showed much closer affinity to Gentianopsis than to a ny other genus. Some conflictions were detected in the genus Swertia.