ORIGINAL ARTICLE Taxonomy of the Andean genus Pentacyphus (Apocynaceae: Asclepiadeae–Pentacyphinae) U. Meve • S. Liede-Schumann Received: 26 March 2014 / Accepted: 7 July 2014 Ó Springer-Verlag Wien 2014 Abstract Taxonomy of the northern Andean genera Pentacyphus and Tetraphysa is re-evaluated by morpho- logical and molecular analyzes. Pentacyphus, while having priority against its synonym Tetraphysa, consists of three species: P. andinus, P. lehmannii, and P. camargoi, based on Sarcostemma camargoi, a species from Colombia and Ecuador which is transferred to Pentacyphus here. More- over, T. tamana is reduced to subspecific rank under P. lehmannii, and an additional subspecies with exceptionally large flowers and corona lobes is newly described as P. lehmannii subsp. elongatus. P. boliviensis, a synonym of P. andinus, is lectotypified. Keywords Andes Á Asclepiadoideae Á Neotropics Á Pentacyphus camargoi comb. nov. Á Phylogeny Á South America Á Tetraphysa Á Taxonomy Introduction In a number of morphological (Liede 1996; Liede and Kunze 1993), molecular-phylogenetic (Liede-Schumann et al. 2005) and taxonomical-nomenclatural studies (En- dress et al. 2014), the position of the two monotypic, exceptionally showy Andine taxa Pentacyphus and Tetra- physa (Apocynaceae–Asclepiadoideae–Asclepiadeae) could be clarified step by step over the last 20 years. These studies included two species, Pentacyphus andinus and Tetraphysa lehmannii. A third taxon described as T. Ta- mana Morillo was not available for investigation (but is regarded as a subspecies of T. lehmannii). And another, fourth element is recognized in the present study as a new, so far undescribed species. Schlechter (1906), when describing the material col- lected in the Andes by August Weberbauer (1871–1948), created five new genera, among them Pentacyphus (1906: 605) and Tetraphysa (1906: 616). Based on her cladistic study, Liede (1996) considered Pentacyphus and Tetra- physa as congeneric and, in consequence, placed Tetra- physa in synonymy of Pentacyphus providing the combination Pentacyphus lehmannii (Schltr.) Liede, based on the type species of Tetraphysa, T. lehmannii Schltr. In addition, she recognized the type species of Pentacyphus, P. boliviensis Schltr., as synonym to Lugonia andina Ball and consequently published the new combination Pentac- yphus andinus (Ball) Liede. Lugonia Wedd., based on L. lysimachioides Wedd., also a species of Peru, is today considered as synonym of Philibertia Kunth (Goyder 2004). Liede (1996) was not aware that Morillo (1994a) had published a second species in Tetraphysa, T. tamana Mo- rillo, and therefore this taxon remained untreated for another year when Liede (1997) published the combination Pentacyphus tamanus (Morillo) Liede. With regard to priority, the ICN (2012: Art. 11.5) states that if ‘‘a choice is possible between legitimate names of equal priority in the corresponding rank … the first such choice to be effec- tively published establishes the priority of the chosen name’’. Morillo (1994a) considered solely Tetraphysa, whereas Liede (1996) considered Pentacyphus and Tetra- physa and finally treated them as congeneric. While mak- ing the corresponding combinations, Liede (1996) unequivocally made her choice, giving Pentacyphus pri- ority against Tetraphysa. This choice, that puts Tetraphysa in synonymy of Pentacyphus, was again emphasized in U. Meve (&) Á S. Liede-Schumann Department of Plant Systematics, University of Bayreuth, Universita ¨tsstraße 30, 95440 Bayreuth, Germany e-mail: ulrich.meve@uni-bayreuth.de 123 Plant Syst Evol DOI 10.1007/s00606-014-1130-9