Peru. Departamento San Martín: Provincia Rioja, distrito Pardo Miguel Naranjos, sector Venceremos, camino al terreno del Sr. Roner Espinal Gómez, 5°41'10.68"S, 77°45'19.17"W, 1756 m a.s.l., 15 June 2022, J. D. Edquén 6111 (holotype: KUELAP 002579!).

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).

Figure 2. 

Liparis altomayoënsis (from Edquén 6111) A plants in habitat (the pen serves as size reference) B column apex from below showing the two pollinaria on the stigmatic cavity C dissection of the perianth D labellum, ventral view E labellum, dorsal view.

Terrestrial, decumbent, glabrous herb 5–15 cm tall including the inflorescence. Roots scarce, dull white, glabrous, arising from the rhizome, up to 15 mm long, ca. 0.5 mm in diameter. Rhizome (prostrate portion of the stems) branching, terete, greenish white, each branch formed by several (up to 10) internodes, 2–5 cm long, 2–3 mm in diameter, partially covered by brownish remains of cataphylls; upright portion of the stem 3.5–8 cm long, 2.5–3.5 mm in diameter, formed by 4–6 internodes, these nearly completely covered by the leaf sheaths. Leaves [2–]3–6 per stem, arranged into a spiral, petiolate; petiole (4–)10–14 × 3–5 mm, semi-tubular, obliquely sheathing the internode; blade 10–25 × 7–15 mm, ovate, acute to shortly acuminate, margins strongly undulate, translucent, 5–7 main parallel veins and several transverse ones, all veins conspicuously raised on the upper surface and slightly sunken on the underside, excepting the slightly prominent central vein; upper surface glossy dark green, lower surface opaque olive green. Inflorescence terminal, 4–7 cm long; peduncle 20–26 mm long, 1–1.5 mm in diameter, with several longitudinal low keels; raceme 2–6 cm long, moderately lax, with 7–20 flowers opening in succession, but most can be open at a time. Floral bracts shorter than the ovaries, divergent from the rachis at flowering, patent at fruiting stage, pale green, lanceolate, acute, 5–7 × 1.3–1.5 mm. Ovary spreading, pedicellate, narrowly obconical, convex dorsally, flat ventrally, slightly 3-angled, 6–6.6 mm long, 1–1.2 mm wide above the middle; about one half of the length corresponds to the twisted pedicel. Flowers resupinate, pale green with a wine–colored ridge at each side of the central cavity of the labellum. Sepals spreading, with revolute margins, 1-veined; lateral sepals obliquely elliptic, rounded, 3.6–3.7 × 1.6–1.7 mm, dorsal sepal linear–lanceolate, rounded and slightly calyptrate at apex, 4–4.1 × 1.2–1.3 mm. Petals spreading, incurved, linear, slightly falcate, rounded, 4–4.2 × 0.5–0.6 mm. Labellum 2.6–2.7 mm total length, 2.7–2.8 mm total width when spread out, sessile, 7-veined, in natural position its basal one-half diverging ca. 60° from the column and the apical one-half in turn deflexed ca. 90°; base provided at each side with a fleshy, rounded, channeled, erect lobule forming a tunnel with the lower half of the column; disc fleshy, deeply concave, provided at each side of the cavity with a obliquely triangular, retrorse, rounded lobe ca. 1 × 0.8 mm, which has an erect ridge projected towards the apex into an acute, narrowly triangular lobule ca. 0.2 × 0.1 mm; cavity limited apically by a transverse, lunate, rounded to obtuse fleshy ridge; apex membranaceous, trilobulate, the lobules rounded, mid-lobule ca. 0.3 × 0.2 mm, lateral lobules much shorter, deflexed in natural position. Column semiterete, clavate, slightly arcuate, lacking auricles, whitish green below the middle, dark green with purplish suffusion near the apex, 1.6–1.8 × 0.7–0.8 mm. Anther apical, incumbent, transverse to the main column axis, whitish, cordiform, emarginate, 2-celled with each cavity partially subdivided in two, ca. 0.2 × 0.4 mm. Pollinaria 2, each consisting of 2 fused pollinia, yellow, obliquely ovoid, granulose, 0.3–0.4 × ca. 0.2 mm. Capsule ascending, ellipsoid, with 6 low longitudinal ribs, to 5 × 3.5 mm plus a filiform pedicel ca. 4.5 mm long, when mature yellowish brown.

Flowering recorded in June and July. Capsules in different stages of development were observed from June to October. Mature, empty dehiscent capsules from the previous year’s flowering were observed in mid-May.

Known only from sector Venceremos of the BPAM. Terrestrial, in deep leaf mold on steep slopes with wet montane cloud forest on a steep tepui (table mountain) slope dominated by dwarfed trees of Clusia L. (Clusiaceae), Meriania Sw., Miconia Mart. (Melastomataceae) and stands of Chusquea Kunth (Poaceae), at 1750–2160 m a.s.l.

The specific epithet refers to the Bosque de Protección Alto Mayo, the protected natural area in northeastern Peru where this species was discovered.

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).

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, pollinator-mediated 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.

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.

Peru. As the type locality, 5°42'41.55"S, 77°44'19.54"W, 2090 m a.s.l., 17 May 2022, J. D. Edquén 6101 (KUELAP!); as the type locality, 5°42'42.73"S, 77°44'31.99"W, 2160 m a.s.l., 4 July 2022, J. D. Edquén 6421 (KUELAP!).