PHYLOGENY OF RUBIACEAE-RUBIEAE INFERRED FROM THE SEQUENCE OF A CPDNA INTERGENE REGION

A phylogenetic analysis of 25 species, representing eight genera of the Rubieae tribe (Rubiaceae), has been made using the DNA sequence of the chloroplast atp B-rbc L intergene region. Six tropical genera from other tribes of Rubiaceae have been used as outgroups. Whatever the method of analysis (distance, parsimony or maximum likelihood), five groups are clearly separated and described as informal clades. Their relative relationships are not clearly resolved by the parsimony analysis, resulting in eight equally parsimonious trees, 327 steps long, with a consistency index (CI) of 0.749 (excluding uninformative sites). The Rubieae tribe appears monophyletic from the data available. Some new and partly unexpected phylogenetic relationships are suggested. The genus Rubia forms a separate clade and appears to be the relatively advanced sister group of the remaining taxa. The Sherardia clade also includes the genera Crucianella and Phuopsis. Galium sect. Aparinoides appears closely attached to the Asperula sect. Glabella clade. The remaining taxa of Galium are paraphyletic: Galium sect. Platygalium (in the Cruciata clade) is linked to the advanced genera Cruciata and Valantia; the more apomorphic groups of Galium form the Galium sect. Galium clade, including the perennial sections Galium, Leiogalium, and Leptogalium as well as the annual (and possibly polyphyletic) sect. Kolgyda.