Taxonomic Revision of Ruellia Section Chiropterophila (Acanthaceae): a Lineage of Rare and Endemic Species from Mexico

Ruellia section Chiropterophila as here recognized contains 11 species endemic to areas in and around the transnational Volcanic Belt of México: the Sierra Madre del Sur, the Balsas Depression, and the Altiplano. Most of these species are rare, and nearly half are known only from one or two collections. Of the remaining six, two are restricted to single states. One species described as new to science, Ruellia laslobasensis , is distinguished from a close relative by its smaller corollas, calyces, and fruits. Ruellia chilpancingana is placed into synonymy with R. sororia. Ruellia section Urceolata is synonymized with sect. Chiropterophila. Two species previously treated in sect. Chiropterophila, Ruellia petiolaris (as R. palmeri) and R. carmenaemiliae, are excluded from the section. Phylogenetic analyses using three chloroplast markers (trnC-trnR, trnG-trnS, psbA-trnH) and one nuclear marker (ITS + 5.8S) were conducted to test the monophyly of sect. Chiropterophila and to reconstruct relationships among species. Sequences were successfully generated for all species in sect. Chiropterophila; some are known only from old herbarium material. One of these, collected in 1894, is among the oldest known plant herbarium specimens to be successfully sequenced. Analyses reveal that section Chiropterophila is monophyletic but not well supported; an alternative hypothesis of nonmonophyly of the section could not be rejected. Species descriptions, botanical illustrations, and a dichotomous key to distinguish the 11 taxa in Ruellia sect. Chiropterophila are provided.