Phylogenetics of New World ‘justicioids’ (Justicieae: Acanthaceae): major lineages, morphological patterns and widespread incongruence with classification

The New World ‘justicioid’ lineage (Acanthaceae: Acanthoideae: Justicieae) includes about 500 species and encompasses extensive variation in flower shape, size, and color along with remarkable diversity in anther, seed, and pollen mophology. Species richness of this lineage is due to the inclusion of the New World members of the polyphyletic genus Justicia in addition to five smaller Neotropical genera: Cephalacanthus, Clistax, Harpochilus, Megaskepasma and Poikilacanthus. Although previous studies have shown that the New World ‘justicioid’ lineage is monophyletic, none have focused specifically on relationships among these plants nor has the current infrageneric classification of Justicia for the New World been tested. This is the first phylogenetic study to include a dense sample of taxa from the New World ‘justicioid’ lineage. We use DNA sequence data for five plastid, nuclear ribosomal ITS, and one low copy nuclear region (8315 bp) for 134 in-group taxa to estimate the phylogenetic ...