A taxonomic synopsis of Acianthera ( Orchidaceae : Pleurothallidinae ) in Peru , including two new species

A taxonomic synopsis of Peruvian Acianthera including 35 accepted species is presented. An artificial key and maps for known localities from all these species are also included. Acianthera berlinensis sp. nov. and A. marleniae sp. nov. are described and illustrated as new species based on specimens collected in the Peruvian regions of Amazonas and Cajamarca, respectively. Information on the distribution and habitat is provided for both new taxa, followed by a discussion comparing the traits that distinguish them from their closest relatives. A. consatae, A. dodsonii, A. lamia, A. scalpricaulis and A. toachica, previously known only from Ecuador and Bolivia, are herein reported for the first time for the Peruvian flora. Resumen. Se presenta una sinopsis taxonómica de Acianthera en Perú que incluye 35 especies. Se incluye una clave artificial y mapas para las localidades conocidas de todas las especies citadas. Acianthera berlinensis sp. nov. y A. marleniae sp. nov. se describen como nuevas especies, basadas en especímenes recolectados en los departamentos de Amazonas y Cajamarca. Se ofrece informacion de su distribución, hábitat y fenología para ambos taxones, seguido de una discusión sobre las características que las distinguen de especies similares. Se citan por primera vez para la flora peruana A. consatae, A. dodsonii, A. lamia, A. scalpricaulis y A. toachica, anteriormente conocidas solo en Ecuador y Bolivia. Damián A., Mitidieri N. & Chiron G. 2018. A taxonomic synopsis of Acianthera (Orchidaceae: Pleurothallidinae) in Peru, including two new species. Anales del Jardín Botánico de Madrid 75 (1): e069. https://doi.org/10.3989/ajbm.2449. Title in Spanish: Una sinopsis taxonómica de Acianthera (Orchidaceae: Pleurothallidinae) en Perú que incluye dos nuevas especies. Received: 23‒VI‒2016; accepted: 28‒II‒2018; published on-line: 12‒IV‒2018; Associate Editor: E. Ortúñez.


INTRODUCTION
Acianthera Scheidw.-Orchidaceae Juss.-is a genus of the subtribe Pleurothallidinae Lindl.ex G.Don that consists of approximately 118-220 species (Pridgeon & Chase 2001;Chiron & van den Berg 2012;Chase & al. 2015; Barros & al. 2016;WCSP 2016).Its distribution covers tropical regions from the Antilles and Mexico to Argentina and Uruguay, being Brazil its main centre of biodiversity (Pridgeon 2005).Members of Acianthera are generally humid-forest or cloud-forest epiphytes from near sea level to over 2600 m a.s.l. and comprises species with more-or-less fleshy flowers, with connivent sepals, the lateral ones connate, lip articulated with the column, which is winged, and two pollinia (Pridgeon 2005;Luer 1986).
Almost two centuries have passed since Michael Joseph Scheidweiler described Acianthera in 1842.After Lindley (1859), species from this group were treated as Pleurothallis R.Br. for many decades, keeping the genus Acianthera under the shade for nomenclatural purposes.Luer (1986) restored the name Acianthera as a subgenus of Pleurothallis in an attempt to accommodate species characterized by slightly fleshy flowers with connate lateral sepals borne singly or in a raceme from the base of the sessile leaf.Nevertheless, recent phylogenetic studies based on DNA (Pridgeon & Chase 2001;Pridgeon & al. 2001;Chiron & van den Berg 2012;Chiron & al. 2012;Karremans & al. 2016) provided strong support for the recognition of Acianthera as a monophyletic group and the necessity to rank it to the generic level.

MATERIAL AND METHODS
For taxonomic treatment, type information was acquired from the protologues of each cited name with the help of Biodiversity Heritage Library -www.biodiversitylibrary.org-and Botanicus -www.botanicus.org-.The type specimens were observed from online photos available through AMES, BM, BR, F, FLAS, K, NY, S, SP, P, US and W -abreviations of the herbaria according to Thiers (2017).
Each species was listed with its complete nomenclature information, including synonyms, original publication and type references.When the holotype was confirmed as destroyed, it was necessary to designate a lectotype.In some cases, we were unable to locate the holotype specimen cited by the protologue, or to be certain about its existence, in such cases we decided to cite as «unknown» rather than proposing a lectotype in order to avoid confusion, since we don't have the certainty of its real status -e.g., Pleurothallis wolfiana Schltr.
Specimens were obtained by revising Peruvian herbaria, USM, HOXA, MOL and CUZ, the latter from online photos available at Atrium -http://atrium.andesamazon.org/-.Through online databases from the AMES, BM, BR, F, FLAS, K, NY, S, SP, P, US and W, localities for all records were georeferenced and superimposed into a map of Peru using Qgis v. 2.18.0 software.New species were photographed in situ using a Nikon D7100/Micro Nikkor 60 mm camera.The holotypes were deposited at UFV. Measurements and description of the morphological features were carried out using a Euromex SB-1903 stereomicroscope.For illustration of the new taxa, alcohol-preserved material was used as well as digital photos that were processed with Adobe Photoshop CC v. 14.0.Plant epiphytic, caespitose, 24 cm tall.Roots 1 mm in diameter, slender, densely fasciculate.Ramicaul stout, erect, terete, 7-14 cm long, enclosed by 2 tubular sheaths near its base.Leaf erect, thickly coriaceous, sessile, elliptical, obtuse, 8-9.5 cm long, 2-2.7 cm wide, the base cuneate, sessile.Inflorescence 1-3 successively 2-flowered racemes, peduncle c. 1 cm long, subtended by a spathaceous bract, ovate 0.5-1 cm long from the base of the leaf; floral bracts infundibular, thin, obtuse, 5 mm long; ovary 4 mm long; sepals fleshy, rigid, microscopically papillate on the margins, yellowish externally, densely spotted with dark purple on the adaxial surface, the dorsal sepal oblong, subacute, 9 mm long, 2-2.5 mm wide, 3-veined, the lateral sepals connate up to near their apices into an ovate synsepal, obtuse, shortly bilobed, 6-veined, 8 mm long, 5 mm wide, each lobe shortly apiculate, the base forming a shallow mentum with the column foot; petals fleshy, yellow, with 3 red rows along the veins, oblong-oblanceolate, somewhat falcate, acute, with margins slightly erose above the middle, thickened at the apex, 3-veined, 5 mm long, 1 mm wide; lip yellowish, covered densely with dark purple dots, fleshy, glabrous, trilobed, oblong-oblanceolate, obtuse, shortly apiculate, 4 mm long, 1.5 mm wide, serrate along the apical margin, the lateral lobes near the middle, erect, uncinate, acute, antrorse, the disc with a pair of smooth low, parallel carinae descending from the lateral lobes and extending toward the apex, the base truncate, thick, shortly concave, hinged to the apex of the column-foot.Column semiterete, 4 mm long, with ventrally extended wings, clinandrium completely covering the anther and denticulate at the margin, the foot thick, 1 mm long, stigma ventral, anther, pollinia and capsule not seen.

Key to the species of Acianthera in Peru
Distribution.-Knownonly from the type locality in the province of Bagua -Amazonas-within «Bosque Berlin» Conservation Area (fig.3).It grows as an epiphyte on low branches of remnant trees of the cloud forest, in semi-shady conditions.Etymology.-Inhonor to ACP-Bosque Berlin, where Leyda Rimarachin and her family make great efforts to preserve a beautiful forest on the high mountains of Bagua -Amazonas-Peru.
Comments.-Thisspecies is somewhat similar to A. biseta Luer, a recently described Peruvian species.As the latter, it belongs to the group of Acianthera characterized by stout, erect, terete ramicauls, thickly coriaceous elliptical leaves and a very short inflorescence bearing 1-2 flowers.However it differs from A. biseta by its wider leaves shorter than the ramicauls -vs.equal to the ramicauls-, its 2-flowered inflorescence -vs.1-flowered-, its smaller flowers -c. 9 mm long versus 16 mm-yellowish with a lip densely dark purple dotted -vs.dull greenish with a deep purple lip), its glabrous sepals -vs.densely and shortly pubescent-, its oblong, 3-veined dorsal sepal -vs.elliptical, 5-veined-, its acute petals with erose margins -vs.obtuse and marginally entire-, its narrower lip with an obtuse mid-lobe -vs.rounded-, without horseshoe-shaped callus at the base.
Comments.-Karremans & al. (2016) proposed a new combination for Pleurothallis brunnescens (A.brunnescens) suggesting that it should be treated as an autonomous species.However, they based their decision on vegetative morphology and conjectures regarding the different flora between Ecuador and Costa Rica.After revising the holotypes of Pleurothallis lojae and Pleurothallis brunnescens, it states clear that both species represent the same concept with slightly variations, Pleurothallis brunnescens present oblong leaves (vs.elliptical) and acute lip (vs.obtuse to oblong).LSID: urn:lsid:ipni.org:names:77176588-1Similar to Acianthera sicula (Luer & Vásquez) Luer but differs in having larger flowers, carinate sepals, fimbriate sub-auriculate petals, and obovoid lip with erose, broadly subquadrate lateral lobes.
Plant small, epiphytic, roots unknown.Ramicauls incomplete, erect, more than 15 cm long, gradually becoming sharply winged above, 0.8-1 cm wide at the junction with the leaf.Leaf erect, coriaceous, narrowly elliptical-ovate, obtuse, 7-9 cm long, 2-4 cm wide, sessile, cuneate, decurrent on the stem for 1-2 cm.Inflorescence in a crowded raceme, with 4-6 distichous flowers reclining on the blade of the leaf, 2.3 cm long, from a spathe 1 cm long at the apex of the secondary stem imbedded well above the base of the leaf; floral bracts 0.4-0.6 mm long; pedicel 3.5 mm long; ovary 3 mm long, densely pubescent; sepals dark purple, densely pubescent on abaxial surface, glabrous within but verrucose in the upper third, the dorsal sepal oblong-obovate, obtuse, 5-6 mm long, 3 mm wide, connate to the lateral sepals for 0.75 mm, the lateral sepals connate to near the apex into a thick, oblong, concave synsepal, carinate, 6 mm long, 4 mm wide, with the apex shortly bifid; petals purple, oblong, obtuse, 4 mm long, 2 mm wide, with the margins sharply fimbriate above the upper third, 1-veined, the base sub-auriculate; lip dark brown, thick, fleshy, obovoid, 3-lobed, 4 mm long, 2.5 mm wide, the apex broadly rounded, densely verrucose with erose margins, the lateral lobes erect below the middle, low, erose, broadly sub-quadrate, 1 mm long, the disc with a thick pair of parallel, verrucose carinae from the base to near the middle, the base hinged to the columnfoot between a pair of membranous auricles; column stout, semiterete, 3.5-4 mm long, with ventrally extended wings, clinandrium entirely covering the anther with lacerate margins , the foot thick, short, 1 mm long, stigma ventral, anther cap cucullate, obovate, capsule not seen.
Distribution.-Peru, in the mountains of Chota -Cajamarca-(fig.10), where it grows as an epiphyte in montane forest at about 2600 m a.s.l.
Etymology.-Inhonor of the senior author's maternal family.
Comments.-Aciantheramarleniae sp.nov. is most similar to A. sicula.Vegetatively, the latter differs by having ramicauls half wider at the apex (5 mm) compared to A. marleniae sp.nov.-1 cm-.Moreover, A. sicula presents cuneate leaves which are decurrent on the stem for less than 1 cm vs. 2 cm in A. marleniae sp.nov.Flowers of A. marleniae sp.nov.are distinguished from those of A. sicula by their larger size, carinate sepals and dark purple-green color -vs.brown, yellow brown-.Petals are quite similar in shape but larger -4 × 2 mm-, sub-auriculate at the base and densely fimbriate in A. marleniae sp.nov. vs. shorter -2.5 × 1 mm-, not auriculate and shortly denticulate in A. sicula.Instead of ovoid, ovate-obtuse lip with lateral lobes rounded in A. sicula, the lip of A. marleniae sp.nov. is obovoid with lateral lobes low, erose and broadly sub-quadrate.

Pleurothallis triangularis
Pleurothallis triquetra Klotzsch ex Lindl., Fol. Orchid. 9: 13 (1859).Type: Venezuela, Dist.Fed., Karsten s.n.(holo-: K).Distribution.-Peru(fig.10), Venezuela, Colombia, Ecuador and Bolivia.WCSP (2016) gives also Brazil, however according to Barros & al. (2016) this species does not exist in Brazil.According to WCSP (2016), A. harpophylla (Rchb.f.) Luer is listed as a synonym of A. polystachya, however this is not fully accurate.Acianthera harpophylla is easily distinguished from A. polystachya by its dorsal sepal, longer than the synsepal -vs.equal length-and its conspicuous intramural calli of the lip with a longitudinal callus from the base to near the apex -vs.low parallel subverrucose calli without a longitudinal callus.stem lenght, while other taxonomically relevant attributes such as petals and lip shape remain constant.Further studies are required to attend if variation among geographically separate populations of A. pubescens could justify its partition into an intra-specific level as subspecies as we suspect.
Comments.-After the clarification of several taxa originally described on the Peruvian expedition of Ruiz & Pavón (Pupulin 2012), it states clear that Hulboldtia polystachya Ruiz & Pav.-A.polystachya (Ruiz & Pav.) Pupulin-represents the first reference to A. cassapensis and should be considered the first available name for the species.In the present work, we follow that conclusion and added a new synonym, A. phyllostachys, treated as different species by Luer on his monograph of the genus and cited by WCSP (2016) as a synonym of A. polystachya without any proper reference.Both, A. casapensis and A. phyllostachys share several vegetative features, including shortly repent habit, compressed above the middle ramicauls and elliptical decurrent leaves.Moreover, the only significant difference in what concern floral morphology between these two species are the longer floral segments of A. phyllostachys -i.e., sepals 13 × 3 mm vs. 10 × 3 mm, petals 5 × 2 mm vs. 3 × 1.5 mm, lip 6 × 3 mm vs. 4 × 2 mm.