Acanthaceae (Asteridae; Lamiales) include ∼4000 species and encompass a range of morphological diversity, habitats, and biogeographic patterns. Although they are important components of tropical and subtropical habitats worldwide, inadequate knowledge of the family's phylogenetic framework has impeded comparative research. In this study, we sampled all known lineages of Acanthaceae including Andrographideae. Also included were eight of 13 genera whose relationships remain enigmatic. We used sequence data from nrITS and four chloroplast noncoding regions, and parsimony and Bayesian methods of analysis. Results strongly support most aspects of relationships including inclusion of Avicennia in Acanthaceae. Excepting Neuracanthus, newly sampled taxa are placed with strong support; Kudoacanthus is in Justicieae, Tetramerium lineage, and the remaining enigmatic genera are in Whitfieldieae or Barlerieae, and Andrographideae are sister to Barlerieae. This last result is unanticipated, but placement of Andrographideae based on structural characters has been elusive. Neuracanthus is monophyletic but placement relative to (Whitfieldieae (Andrographideae + Barlerieae)) is weakly supported. Many clades have clear morphological synapomorphies, but nonmolecular evidence for some remains elusive. Results suggest an Old World origin with multiple dispersal events to the New World. This study informs future work by clarifying sampling strategy and identifying aspects of relationships that require further study.
We uscil molecular sequence data from the tuiclear ribosonial inlernal Iranscribed spacers and from the inlron and spacer of the (niL'trnV chloroplast region to study phylogenelic relationships within the large (ca. 2(KKJ species), wideranging, and taxonomically difficult tribe Justici(\ie (Acanthaceae). The partition homogeneity test indicated tlial the data sets for the two loci were congnient, and sejiarate analyses of the two gave similar results. Analysis of the combined data set [)rovitles a highly resolved hypothesis of relationships, much of it strongly sup[)()rted. Justicieae are strongly supported as monopliyletic; within the tribe, five lineages and one parajjli)letic grade are related as follows: \Pseuderanthemum lineage (Isoglossinae [Teiramcrium lineage [multijih* clades of Old World "justicioids" (Dichpterinae + New World "justicioids")]})]. Many aspects of this phvlogenetic hypothesis are supported by data from morphology and cytology, and some conform to earlier classifications of the grou[). There are, however, a number of novel aspects. Notably, the large genus Juslicia (ca, 700 species) is not monophylctic; the Old World members form a grade and the New World members are monophylctic only if a number of odier genera are included. The very strongly supported sister-group rehitionship between Dichpterinae and the New World "justicioid" lineage is novel, and we cannot identify non-molecular synapornorphies to confirm this relali(niship. Rliindcanllius. a "juslicioid'' {Justuia and mor])hol(>gica]ly similar genera) by all but ph}logenclic criteria, is strongly supported as a basal member of Diclipterinae, and cytological evidence confirms this placement. The Pscuderanlheriiufii lineage is only modestly supported as monophylctic and may, in fact, represent a series of basal bneages. These plants an^ marked by having four staminal elements (four stamens or two stamens plus two staminod**s). a plesiomor[)hic condition for all Acanthaceae. Additional evidence (bolli laxa and characters) will be necessary' to resolve this uncertainty, as well as to determine die phylogenetic status of Old World "justlcioitls." Our analysis does provide considerable resolutujn of relationships within mono|)liyletic lineages, and these relationships are discussed in the context of non-molecular evidcnice and previous classifications.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.