Homoplasty increases phylogenetic structure

According to currently accepted theories, rapidly evolving nucleotide sites are phylogenetically less informative than more slowly evolving ones, espe cially for recognizing more ancient groupings. For this reason third codon positions are often regarded as less reliable than first and second positio ns as indicators of phylogeny. Analysis of the largest nucleotide matrix tr eated to date-2538 rbcL sequences covering all major lineages of green plan ts-shows the opposite: although rapidly evolving and highly homoplastic, th ird positions contain most of the phylogenetic structure in the data. Frequ ency of change should thus be used with caution as a criterion for weightin g or selecting characters, (C) 1999 The Willi Hennig Society.