Phylogenetic relationships among Acanthaceae: Evidence from two genomes

we used sequence data from the nuclear ribosomal internal transcribed space r (nr-ITS) region, both alone and in combination with data from the intron and spacer of the trnL-trnF chloroplast (cp) region, to study phylogenetic relationships within the large tropical and subtropical family Acanthaceae. Substitution rate in the nr-ITS region is nearly twice that of the trnL-tr nF cp region, and more than twice the rates of other cp loci that have been sequenced for members of Acanthaceae (i.e., rbcL, ndhF). In terms of phylo genetic relationships, the hypothesis based on ITS was largely congruent wi th the trnL-trnF results. Exceptions are Crossandra pungens and the two Aca nthus species, which are placed enigmatically by nr-ITS data. The combined analysis provides strong support fur a single hypothesis of relationships a mong Acanthaceae sensu stricto (s.s.) and their closest relatives. 1) Elytr aria (representing Nelsonioideae) is more distantly related to Acanthaceae s.s. than Thunbergia and Mendoncia. 2) These last two genera are sister tax a and together are the sister group of Acanthaceae s.s. 3) Acanthaceae s.s. are monophyletic. 4) There are at least four major monophyletic lineages w ithin Acanthaceae ss.: the Acanthus, Barleria. Ruellia, and Justicia lineag es. 5) These four lineages are related as follows: {Acanthus lineage [Barle ria lineage (Justicia + Ruellia lineages)]}. 6) Within the Justicia lineage , there are at least five monophyletic sublineages, related as follows: {Od ontonema sublineage {Stenostephanus sublineage (Henrya sublineage {Diclipte ra + New World justicia sublineages})]}.