﻿A new species of Liparis (Orchidaceae, Epidendroideae, Malaxidinae) from the Bosque de Protección Alto Mayo, San Martín, Peru

﻿Abstract Liparisaltomayoënsissp. nov. is described, illustrated, and tentatively assigned to the Neotropical section Decumbentes on the basis of its branching, prostrate rhizomes and upright stems bearing several leaves. Vegetatively, the new species is distinguished by its short, upward stems bearing 3–6 leaves, these with undulate, translucent margins and reticulate, prominent veining on the upper surface. Florally, it is distinctive in the labellum with fleshy basal one-half provided with a central, rounded cavity limited on each side by a prominent, bilobulate ridge and apically by a lunate ridge, and membranaceous, trilobulate apical one-half deflexed ca. 90°. In contrast with other species of section Decumbentes, in which fruit formation is infrequent, in L.altomayoënsis a high proportion (⁓50–100%) of flowers develop into a fruit; in some flowers the pollinaria rotate and contact the stigma, apparently resulting in at least facultative self-pollination. The main differences among the six species of L.sectionDecumbentes hitherto known are contrasted in a dichotomous key. The new species is known only from three populations located in the Bosque de Protección Alto Mayo, on the Amazonian slope of the Andes in northeastern Peru but appears to be under no foreseeable threats.


Introduction
The genus Liparis Rich. consists of about 320 epiphytic and geophytic species and is widely distributed in tropical, subtropical, and temperate regions of the Old and New Worlds, being distinguished from other members of Malaxidinae mainly by the elongate column with an apical, incumbent anther (Ridley 1886;Cribb et al. 2005). Although several molecular phylogenetic studies have shown that Liparis is polyphyletic (Cameron 2005;Tang et al. 2015;Li et al. 2020;Ya et al. 2021;Wang et al. 2022), such studies have been strongly biased towards tropical/subtropical Asian taxa. Many Neotropical species have not yet been included in molecular analyses, and much work remains to be done to attain a clear picture of generic limits and relationships in this region. Meanwhile, the morphology-based sectional classification proposed by Garay and Romero-González (1999) provides a framework for taxonomic discussion and comparison of morphologically discrete groups.
Liparis section Decumbentes Garay & G.A.Romero is endemic to the Neotropics and distinctive in the decumbent, creeping stems with distichously arranged leaves (Garay and Romero-González 1999; Fig. 1). This poorly known group is restricted to Andean cloud forests from Venezuela south to Bolivia, and included five species, two of them only recently described from Peru (Damián et al. 2020;Salazar et al. 2022).
In this work, we propose an additional species tentatively assignable to Liparis section Decumbentes, discovered during fieldwork conducted as part of our ongoing orchid inventory of the Bosque de Protección Alto Mayo, San Martín, Peru (BPAM; J. D. Edquén et al. in prep.). The new species is described and illustrated, and the features permitting to distinguish the currently known six members of Liparis section Decumbentes are compared in a dichotomous key.

Materials and methods
Live plants were studied in situ and photographed with a digital camera (Nikon 850, Nikon Corporation, Tokyo, Japan) provided with a 60 mm AF Micro Nikkor lens (Nikon). Leaves and flowers preserved in ethanol 70% were examined and photographed under a stereomicroscope (Stemi SV 6, Carl Zeiss Mikroskopie, Jena, Germany) using a cell phone (iPhone 11, Apple Inc., Cupertino, USA). All images were processed for plate preparation with ADOBE PHOTOSHOP v. 24.0.1 (Adobe Inc., San Jose, USA). Three specimens from different locales were pressed and deposited in the herbarium of the Universidad Nacional Toribio Rodríguez de Mendoza, Chachapoyas, Peru (KUELAP); one of them was designated as the holotype. Measurements were made on the pressed specimen and the alcohol-preserved specimens. Our material was compared with the protologues and additional literature, types, and records of types of all previously described species of New World Liparis, especially those belonging to section Decumbentes, to which our material shows similarities. The collections of several major herbaria in Peru and abroad were studied, including AMES, AMO, CUZ, F, GH, HOXA, K, KUELAP, MEXU, MO, MOL, NY, QCE, QCNE, UFV, US, and USM (herbarium acronyms according to Thiers 2022). The new species was compared on morphological grounds to other members of section Decumbentes and the main differences were incorporated into a key to the six hitherto recognized species belonging to this section. Diagnosis. Liparis altomayoënsis is characterized by the short prostrate rhizomes and upright stems (to 5 and 8 cm long, respectively); 3-6 spirally arranged leaves per stem; leaves petiolate, the blades with strongly undulate, translucent margins and reticulate veining prominent on the upper surface and sunken on the underside. The labellum is slightly wider than long, its base provided at each side with a fleshy, rounded, channeled, erect lobule forming a tunnel with the lower half of the column; basal one-half of labellum provided with a central, rounded cavity limited on each side by a prominent, bilobulate ridge and apically by a lunate ridge; apical one-half of labellum membranaceous, trilobulate, deflexed ca. 90°. (Figs 1F-H, 2C-E).
Phenology  Etymology. The specific epithet refers to the Bosque de Protección Alto Mayo, the protected natural area in northeastern Peru where this species was discovered.
Taxonomic notes. We tentatively include the new species in Liparis section Decumbentes because of its branching, prostrate rhizomes and upright stems bearing several leaves (Fig. 1A, B). However, in many other respects it differs from the five previously known species of the section, and its systematic position will have to be revised when material suitable for molecular analysis is available. Vegetatively, L. altomayoënsis differs from all other species of section Decumbentes in its comparatively short, upward stems bearing only a few (3-6) spirally arranged leaves with strongly undulate, translucent margins and reticulate veining, with the veins prominent on the upper surface and sunken on the underside (Fig. 1C). Florally, the most distinguishing feature of the new species is the unusual morphology of the labellum, which is slightly wider than long. The basal one-half of the labellum is fleshy, diverges from the column about 60° and has a retrose lobe on each side and a central, rounded cavity limited on each side and the apex by prominent ridges; the apical one-half of the labellum is membranaceous, deflexed ca. 90° with respect to the basal one-half, and 3-lobulate (Fig. 1F, G). The lateral labellum ridges consist of a proximal, retrorse, obtuse lobule and a forwardly projecting, narrowly triangular distal lobule. The apical ridge limiting the cavity is unlobed, lunate, and rounded or obtuse. The column is semiterete, clavate, slightly arcuate, lacking auricles and the anther is terminal, transverse to the main axis of the column (Fig. 1E, I-K). The features allowing for the distinction of the six species hitherto known of L. section Decumbentes are highlighted in the key (see below).
Reproductive biology. Unlike other species of Liparis section Decumbentes, in which fruit production seems to be very rare (cf. Damián et al. 2020;Salazar et al. 2022), a surprisingly high percentage (⁓50-100%) of flowers of the plants of L. altomayoënsis we examined were developing into a fruit (Figs 1A, B, 2A). Such high frequency of fruit formation is similar to that recorded in self-pollinating populations of other, distantly related species of Liparis, such as eastern Asian L. kumokiri F.Maek. of section Liparis (Oh et al. 2001). We were unable to verify in the field possible evidence of self-pollination, but we could not remove the pollinaria of several fresh flowers examined and photographed in situ, and subsequent examination of the columns of six alcohol-preserved flowers under a stereomicroscope revealed that, in two of them, the two pollinaria were in contact with the stigmatic cavity, as if they had rotated downwards with the rostellum acting as a sort of hinge (Fig. 2B). A similar rotation of the pollinaria to contact the stigma has been suggested as a mechanism of self-pollination, probably promoted by the dislodgement of the anther by raindrops, in other species of Liparis such as L. loeselii (L.) Rich. in eastern North America (Catling 1980) and L. kumokiri in Japan (Suetsugu 2019). Facultative autonomous self-pollination resulting from rotation of the pollinarium such that the pollinia contact the stigma has been recorded in some populations of species of other Epidendroideae genera, such as Eulophia alta (L.) Fawc. & Rendle (Goss 1973;G.A. Salazar, pers. obs.), Eulophia maculata (Lindl.) Rchb.f. (as Oeceoclades maculata (Lindl.) Lindl.; Aguiar et al. 2012: fig. 4), and various species of Corallorhiza Gagn. (Catling 1990 and references therein;Freudenstein 1997;G. A. Salazar pers. obs.). Hence, there is a possibility that at least some of the many capsules observed in L. altomayoënsis may have resulted from self-pollination by the spontaneous rotation of the pollinaria. However, in fresh flowers of L. altomayoënsis the labellum is distinctive glossy, especially the raised borders of the basal cavity and the bottom of the cavity itself, suggesting nectar mimicking, as proposed for other Liparis having a glossy central band along the labellum (Oh et al. 2001). We were unable to verify whether the cavity contains nectar, which has been shown to be present at least in small quantities in some species of Liparis (Margońska et al. 2019;Suetsugu 2019). The presence of nectar or a nectar-mimicking glossy surface are suggestive of visitation and probable cross-pollination mediated by insects. At the present time, it is not clear whether the high fruit set observed in L. altomayoënsis is the result of self-pollination, pollinatormediated cross pollination, or both, and the factors underlying its high success in setting fruit will have to be clarified by carefully designed field and laboratory experiments.
Conservation assessment. The BPAM was established in 1987 by the Peruvian government to protect the water sources for agriculture, industrial use, and human consumption in the valley of the Upper Mayo River, as well as to conserve the fauna and flora (Servicio Nacional de Áreas Naturales Protegidas por el Estado 2023). It encompasses 182,000 ha of rugged mountainous terrain on the eastern (Amazonian) slope of the Andes in the northwestern portion of the Department San Martín and adjacent areas of Departments Amazonas and Loreto (ca. 5.4°-6.2°S, 77.2-77.8°W), covering an elevation interval from ca. 900 to 3800 m a.s.l. The vegetation includes wet lower montane forest, montane rain/cloud forest, and high-elevation grassland. Liparis altomayoënsis is known only from three stands (populations) of various dozen plants located on the northwestern portion of the BPAM (sector Venceremos) on a steep tepui slope. There were no signs of human alteration or potential risk factors to the populations, which are under legal protection within the BPAM. Moreover, there are large expanses of potentially suitable habitat that remain to be explored, which suggests that this species is not an immediate conservation concern, as long as its habitat remains unaltered.
Additional specimens examined.