Phytotaxa 372 (4): 291–295 http://www.mapress.com/j/pt/ Copyright © 2018 Magnolia Press Article PHYTOTAXA ISSN 1179-3155 (print edition) ISSN 1179-3163 (online edition) Accepted by Cássio van den Berg: 19 Sept. 2018; published: 19 Oct. 2018 https://doi.org/10.11646/phytotaxa.372.4.6 291 A new species of Acianthera (Pleurothallidinae, Orchidaceae) from Brazil MAX RYKACZEWSKI 1 , WIEL DRIESSEN 2 & MARTA KOLANOWSKA 1,3* 1 Department of Plant Taxonomy & Nature Conservation, The University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland; e-mail: marta.kolanowska@wp.pl 2 Loosteeg 7, 5981 NH Panningen, Netherlands 3 Global Change Research Centre AS CR, Belidla 986/4a, 60300, Brno, Czech Republic Abstract A new species of Acianthera from Brazil is described and illustrated here. The novelty belongs to the nominal subgenus of Acianthera and it resembles Acianthera hystrix and A. portilloi but it is easily distinguishable by the external and internal pubescence of the sepals, the pubescent ovary and the lip disc ornamented with three lamellae. A dichotomous key to identification of all known species of Apoda-prorepentia group is provided. Keywords: biodiversity, new species, taxonomy, orchids, South America Introduction The genus Acianthera Scheidweiler (1842: 292) was described based on a Brazilian plant, named A. punctata Scheidweiler (1842: 292), characterized by basally connivent sepals, connate lateral sepals, cuneiform petals, 3-lobed lip articulated with the column, and alate gynostemium with lacerate apex. The genus has been forsaken until 1986 when Luer established Pleurothallis Brown (1813: 211) subgen. Acianthera Luer (1986: 12) to accommodate species resembling A. punctata. This polymorphic taxon was divided into six sections based on form of ramicaul (compressed vs round in cross-section, 2- or 3-edged), sheathing of ramicaul, composition of inflorescence, and sepals morphology. Further molecular studies (Pridgeon & Chase 2001) resulted in the re-establishment of Acianthera at the generic rank. In this recognition of Acianthera the genus included also representatives of Pleurothallis subgen. Arthrosia Luer (1986: 34), P. subgen. Sarracenella (Luer 1981: 388) Luer (1986: 73) and P. subgen. Specklinia (Lindley 1830: 8) Garay (1974: 121-123) sect. Muscosae Lindley (1842: 82). More recently Acianthera was divided into four subgenera (Karremans et al. 2016): Acianthera, Antilla (Luer 2000: 39) Karremans (2016: 183), Brenesia (Schlechter 1923: 200) Karremans (2016: 184), and Kraenzlinella (Kuntze 1904: 310) Karremans (2016: 184). The nominal one comprises 268 species, previously classified in various smaller genera (Karremans et al. 2016). The great variation observed in the morphology of representatives of subgen. Acianthera is not reflected in the sectional division of the subgenus. That makes this taxon difficult to characterise accurately and cause inconvenience in species classification. A first attempt, based on 63 species only, has been proposed by Chiron & van den Berg (2012). Nevertheless, Karremans et al. (2016) suggested that systematic division should be done in the future, to clarify the morphological distinctness between species (Karremans et al. 2016). A distinctive group of species within the subgen. Acianthera is composed of species previously classified within Pleurothallis subgen. Apoda-prorepentia Luer (1986: 31). This taxon was later elevated to the rank of separated genus Apoda-prorepentia Luer (2004: 255). These plants are characterized by the pendent or repent habit, the ramicauls being much shorter than the coriaceous leaves which are basally cuneate into a sessile base, the short, single to successively flowered inflorescence with prominent spathe, abbreviated pedicel and the flowers fleshy, often pubescent sepals (Luer 2007). Representatives of Apoda-prorepentia are distributed from Mexico and Central America, through Caribbean to Peru and Brazil in South America. Most species are rather restricted in their geographical range, however, populations of Acianthera testifolia (Swartz 1788: 122) Solano Gómez (2011: 50) are found across Mexico to Costa Rica and Venezuela. The altitudinal range of the genus extends from 200 up to 3,000 m. Here we present a new Acianthera species belonging, based on its morphological characters, to the Apoda- prorepentia complex. A key to identification representatives of this not monophyletic group is provided.