A new species and a new record of Liparis sect. Decumbentes (Malaxidinae, Orchidaceae) from Peru

Abstract A new species of Liparis sect. Decumbentes, Liparis sessilis Damián, Salazar & Rimarachín, sp. nov is described and illustrated from Amazonas (Perú), including color photographs, a detailed comparison and an identification key to all the species of Liparis sect. Decumbentes. In addition, we report Liparis brachystalix Rchb.f. for the first time for the orchid flora of Peru, and select a lectotype for its synonym, L. commelinoides Schltr.

The most recent proposal of a sectional classification of Liparis by Garay and Romero-González (1999) recognized 19 sections, but their monophyly has not been assessed. One of the sections proposed by Garay and Romero-González (1999), sect. Decumbentes, consisted of 4 South American species and was typified with Liparis brachystalix. This species was originally described from a plant collected in the surroundings of Quito (Reichenbach 1876) and was illustrated by a painting from a Colombian plant by Manuel Antonio Cortes (Mutis 1969: pl. 575;Fernandez 1992) executed during the Royal Botanical Expedition to the New Kingdom of Granada led by Jose Celestino Mutis. Cortes painted the plant more than 40 years before W. Jameson collected it in Ecuador but the results of the expedition remained unpublished until the 20 th century. Members of sect. Decumbentes are characterized by their decumbent or prorepent stems provided with secund or alternate leaves, and according to Garay and Romero González (1999) have an elongated column typical for the genus. However, most of the representatives included in this group (Table 1) have a short, straight column similar to that seen in Crossoglossa Dressler & Dodson (this last genus was treated by Garay and Romero-González as Liparis sect. Tipuloidea). Liparis crispifolia Rchb. f.is an exception, having a slender, arcuate column.
In Peru, sect. Decumbentes is represented by 3 species: Liparis brachystalix, L. laticuneata C. Schweinf. and a new species, in the following referred to as L. sessilis Damián, Salazar & Rimarachín. These are mostly restricted to the eastern slopes of the Andean Cordillera in the departments of Amazonas, Cusco, Pasco and Huancavelica where they grow as terrestrial (rarely epiphytic) plants between 2000-3000 m a.s.l. Liparis crispifolia has been cited for Peru by several authors, all of them following the dubious record of Schlechter (1921), who indicated "Cajamarca (?)" [sic]. Schweinfurth (1959) explicitly stated "fide Schlechter" in attributing this species to Peru, and subsequent works appear to have simply followed him (Brako and Zarucchi 1993;Zelenko and Bermúdez 2009;Goicochea et al. 2019). However, this taxon is endemic to the surroundings of Quito (Ecuador), where the type came from according to Reichenbach´s protologue, and recently re-collected in the same region (Dodson 1989;Dodson 2002; both reports misidentified as L. nigrescens).
During a field exploration conducted in the Private Conservation Area of the Berlin Forest (PCA BF), a protected area located in the northeast part of Peru, we collected Decumbentes. After an extensive review of literature and herbaria we concluded that this specimen did not match any Liparis species described to date, and here we propose it as new. In the following, we provide a detailed description, a line illustration, color photographs and brief notes about the ecology of this specimen, and we compare it with other members of sect. Decumbentes.

Materials and methods
A live flowering plant of the new species was collected on March 9, 2016 while conducting a floristic study in Bosque Berlin (Amazonas). The species was photographed in situ and also from ethanol preserved floral material using a Nikon D810 camera with Nikkor 60 mm lens. Herbarium specimen were prepared to be used as type material, and deposited at UFV and HUT (Acronyms following Thiers 2019). Descriptions and measurements were carried out under an Euromex SB-1903 and an AmScope SM-3TZ-54S-10M stereomicroscopes. The line illustration of the new species was prepared from alcohol-preserved material and digital photos. A total of 31 exsiccates of other members of Liparis sect. Decumbentes were compared for this work from the following herbaria: USM, MOL, HOXA, AMAZ, HUPCH, HSP, F, MO, HNOP, MEXU, QCE, QCNE and NY. We conducted a careful comparison of the new species with the protologues and type material of all species belonging to Liparis sect. decumbentes, as well as regional floras and checklists such as Schweinfurth (1959), Brako and Zarucchi (1993) and Ulloa Ulloa et al. (2004, 2017. Description. Terrestrial or epiphyte, long-creeping herb. Stem elongate, decumbent, laterally compressed, green, 2 mm in diameter, up to 35 cm. Leaves distichous, sessile, ovate, acute, with a narrow base clasping the stem, the margins undulate, 3veined, 2.5-3.5 cm long and 1-1.5 cm wide. Inflorescence terminal, erect, racemose, producing many (up to 20) flowers in succession, peduncle terete in cross-section, provided with conspicuous glandular trichomes up to 6 mm long. Floral bracts pale greenish, narrowly triangular, margins undulate, 7-8 mm long and 2 mm wide. Ovary terete, with longitudinal keels, pale greenish, to 8 mm long including the pedicel. Flowers resupinate, widely spreading, sepals, petals and column pale greenish, labellum green, darker towards the center on the basal one-third. Dorsal sepal lanceolate, apex convex, broadly triangular, obtuse, margins revolute, 1-veined, 6-7.5 mm long and 1-1.5 mm wide. Lateral sepals lanceolate, slightly oblique, broadly rounded, margins revolute, 1-veined, 8 mm long, 2 mm wide. Petals linear, truncate with a rounded mucro, margins irregular, revolute, 1-veined, 7.5 mm long, 1 mm wide. Labellum ovate-elliptic, apex obtuse, upper lateral margins irregularly erose, 11-veined, 10-12 mm long, 4-5 mm wide, ecallose, with a squarish fovea above the base, medially with two low ridges converging up to three-quarters of the lamina. Column short, stout, 1.7 mm long; anther cucullate, 2-celled. Pollinia 2, obovate. Fruit unknown.
Etymology. The specific epithet refers to the distinctive sessile leaves of the species. Distribution and ecology. This species inhabits the cloud forests around the river Utcubamba in the province of the same name in the district of Bagua Grande. This area is known as "El Higuerón" and is legally administered by the Rafael Cotrina family. This family, together with that of the third author, are conducting research and conservation programs about the yellow-tailed woolly monkey Lagothrix flavicauda Humbolldt and its habitat in the PCA BF. Flowers have been recorded in March and April.
Liparis sessilis inhabits the understory rich in mosses, rocks and old stems of Anthurium Schott and Psychotria L. species. Also, this species has been using Palicourea shrubs as its phorophyte and can reach up to 2 m above ground. The roots of Liparis sessilis are poorly developed and the stems turn white or brownish as the younger parts of the plant grow. According to recent observations (Rimarachín pers. obs.), the population of this species is small. Indeed, it has only been found in a degraded area and in two other zones of primary forest. The species has been propagated from cuttings and is currently being grown in the PCA BF.
Comments. Among the four species belonging to Liparis sect. Decumbentes, L. sessilis is most similar to L. brachystalix, which differs in having petiolate leaves and different labellum morphology. Liparis sessilis is easily distinguished from other members of its section by the features indicated in the key and in Table 1.