MOLECULAR EVOLUTION AND PHYLOGENETIC IMPLICATIONS OF INTERNAL TRANSCRIBED SPACER SEQUENCES OF RIBOSOMAL DNA IN WINTERACEAE

The internal transcribed spacers and the 5.8S coding region of nuclear ribosomal DNA were sequenced and analyzed to address questions of generic relationships in Winteraceae. The molecular data generated a single tree that is congruent with one based on morphological data. The sequences of ITS 1 in the family range from 235 to 252 bases in size and of ITS 2 from 213 to 226 bases. The size of the 5.8S coding region is 164 bases. The range of ITS 1 and ITS 2 sequence divergence between pairs of genera within Winteraceae is relatively low in comparison to other plant families. Two types of ITS 1 and ITS 2 sequences were observed in the same individual for some taxa. Sequence variations between the two arrays are 4.7%-6.3% for ITS 1 and 5.1%-7.0% for ITS 2. Both arrays of sequences, however, generate the same phylogenetic relationships. Rates of nucleotide substitutions for the internal transcribed spacers are 3.2-5.2 x 10(-10) substitution per site per year estimated in ITS 1 and 3.6-5.7 x 10(-10) in ITS 2.