Subtribal Relationships in Tribe Tradescantieae (Commelinaceae)Based on Molecular and Morphological Data

Tribe Tradescantieae (Commelinaceae) consists of seven subtribes and 25 genera. Previous attempts to evaluate phylogenetic relationships within the group using morphology or the chloroplast-encoded rbcL have either been highly homoplasious (morphology) or provided only weak support for subtribal relationships due to insufficient variability (rbcL). In this study, phylogenetic analysis of nucleotide sequence data from the chloroplast-encoded ndhF and rbcL genes, as well as 47 morphological and anatomical characters, were used to evaluate relationships within and among the subtribes of Tradescantieae. The addition of ndhF resulted in a more highly resolved phylogeny and greater bootstrap and decay values than were obtained by rbcL alone or rbcL and morphology. The analyses suggest the following: (1) subtribes Coleotrypinae, Cyanotinae, and Tradescantiinae (with the addition of Elasis) are monophyletic; (2) subtribe Thyrsantheminae is polyphyletic; and (3) subtribe Dichorisandrinae is polyphyletic. Members of Dichorisandrinae are united into two clades (Dichorisandra and Siderasis; Cochliostema, Geogenanthus, and Plowmanianthus) whose relationships are more clearly resolved. The position of Old World subtribes Cyanotinae and Coleotrypinae, nested within New World taxa suggested by rbcL studies, are supported by the addition of ndhF data.