Recircumscription and two new species of Pachystachys ( Tetramerium lineage: Justicieae: Acanthaceae) A. L. A. Côrtes, T. F. Daniel and A. Rapini A. L. A. Côrtes (http://orcid.org/0000-0003-1540-0165) (analuiza.cortes@gmail.com), Faculdade Guanambi. São Sebastião, Guanambi, Bahia, Brazil; ALAC also at: Univ. Estadual de Feira de Santana, Programa de Pós-graduação em Botânica, Feira de Santana, Bahia, Brazil. – T. F. Daniel, California Academy of Sciences, Dept of Botany, San Francisco, USA. – A. Rapini, Univ. Estadual de Feira de Santana, Programa de Pós-graduação em Botânica, Feira de Santana, Bahia, Brazil. Phylogenetic studies in Acanthaceae revealed that Schaueria azaleiflora and three species of Streblacanthus are closely related to the genus Pachystachys. In the present study, we propose the enlargement of Pachystachys to reflect these relationships. Two new species are described and illustrated, P. gracilis from Brazil and P. linearibracteata from Peru, and four new combi- nations are proposed in the genus. A key to identify the 18 species of Pachystachys s.l. is also provided. Advances in Acanthaceae phylogenetics have supported new taxonomic circumscriptions in the family (Scotland and Vollesen 2000, Schwarzbach and McDade 2002, Kiel et al. 2006, Daniel et al. 2008, McDade et al. 2008, Tripp et al. 2013) and studies of the ‘ Tetramerium lineage’ (sensu Daniel et al. 2008) have revealed that several traditional genera are non-monophyletic: Anisacanthus Nees, Carlowrightia A. Gray, Mirandea Rzed., Streblacanthus Kuntze and Yeatesia Small. While some generic relationships are still unresolved, others are clearly supported and can be implemented in the system- atics of the group. For instance, although the type species of Streblacanthus, S. monospermus Kuntze, diverged near the root of the ‘ Tetramerium lineage’, the other three species of the genus form a grade near Pachystachys Nees (Daniel et al. 2008, our Fig. 1, based on results from Côrtes et al. 2015). Lindau (1895a) treated Pachystachys and Streblacanthus in different tribes: Pachystachys in Graptophylleae and Streblacanthus in Odontonemeae. Species of Streblacanthus were described in or transferred to Pseuderanthemum Radlk. based on superficial similarities (Radlkofer 1883, Guillaumin 1926, Durkee 1978, Daniel 1993). Neverthe- less, Pseuderanthemum bears two staminodes (absent in Streblacanthus), constricted (vs clavate) capsules and chro- mosome numbers of n = 21 (vs n = 18). Bremekamp (1965) included both Graptophylleae and Odontonemeae in an enlarged circumscription of Justicieae, but the close rela- tionship between Streblacanthus and Pachystachys was only detected in phylogenetic studies based on molecular data (McDade et al. 2000). Prior to the 1980’s, studies treating Pachystachys and Streblacanthus were mainly restricted to descriptions of spe- cies (Ruiz and Pavon 1798, Nees 1847a, 1847b, Kuntze 1891, Lindau 1907, 1912, Rizzini 1947). A revision of Pachystachys (Wasshausen 1986) added nine species to the genus that hitherto had only three, and an unpublished revi- sion of Streblacanthus (Smick 2004) recognized five species, including a new one. Both genera are highly ornamental, erect shrubs 1.5–2.5 m tall; their leaves are green (or some- times adaxially either purplish or with white spots), usually large, ovate to elliptic, and cordate to truncate or cuneate at the base; the inflorescences are long spikes with narrow or broad leaf-like or petaloid, green or yellow bracts; the flowers are relatively large and red, pink or white. Plants can be readily propagated from cuttings, prefer shade and humidity, but can also be grown in open places with filtered light. In nature, they flower from June to November, but some cultivated species, such as Pachystachys lutea Nees and P. spicata (Ruiz & Pav.) Wassh., may be evergreen and flower throughout the year. Pachystachys and Streblacanthus differ from each other by floral characters, possibly reflecting different pollination systems (Faegri and Pijl 1979, Endress 1994): Pachystachys possesses flowers with large red or white corollas, with the curved tube distally broadened, suggesting hummingbird pollination (Wasshausen 1986), while Streblacanthus pres- ents medium-sized flowers with pink to lilac corollas with an erect and straight tube, suggesting butterfly pollination (Smick 2004). In Pachystachys, as traditionally defined, bracts are usually broad, foliaceus or petaloid; narrow or small bracts are typical in Streblacanthus, but can also be found in some species of Pachystachys, namely P. badiospica Wassh. and P. linearibracteata (sp. nov., below). Schaueria azaleiflora Rusby, which also possesses narrow bracts, together with species of Streblacanthus, form a grade basal to Pachystachys (our Fig. 1, © 2016 Te Authors. Nordic Journal of Botany © 2016 Nordic Society Oikos Subject Editor: Bertil Ståhl. Editor-in-Chief: Torbjörn Tyler. Accepted 12 February 2016 Nordic Journal of Botany 000: 001–007, 2016 doi: 10.1111/njb.01126, ISSN 1756-1051 Early View (EV): 1-EV