XVI International Botanical Congess

Current estimates of seed plant phylogeny are based on plastid and nuclear DNA sequences. Mitochondrial genesClargely unused for plant molecular phylogenetics Chave several advantages, including low rates of base substitution, east of alignment, and universal occurrence. Analysis of over 100 coxI gene sequences (ca. 144,000 bp total) provides support for most major lineages identified in analyses of plastid rbcL. A monophyletic Asteridae s.1. and a eudicot clade were recovered with Gunnera, Trochodendron, and Tetracentron as sister lineages. In the monocot clade, Burmannia and Acorus were resolved as basal-most. Unlike rbcL. Gntales is not sister to angiosperms, but forms a strongly supported clade with conifers. Overall, coxI sequences yield trees with low homoplasy and high taxon sampling stability, but lack enough shared variable character to provide well supported relationships among many groups of closely related taxa.