Pleurothallis monteroae M. M. Jiménez, F. Ramón & Mark Wilson sp. nov.

Figs 6, 7, 12 C

Diagnosis

Diagnosis. Similar to Pleurothallis phymatodea, from which it differs in the elliptic to ovate, acuminate leaves (vs. ovate, acute), the 5 - veined, obtuse dorsal sepal (vs. 3 - veined, subacute), the subacute to shortly acuminate synsepal (vs. obtuse), the ligulate, 3.9–4.6 mm long, attenuate petals (vs. oblong, ca. 2.2 mm long, obtuse); and the lip with T-shaped cavity and a glenion (vs. with a narrowly elliptic cavity without a visible glenion), the revolute margins (vs. involute), the obtuse apex (vs. rounded).

Holotype.

Ecuador • Zamora-Chinchipe: Cerca de El Plateado, 6 August 2025, M. M. Jiménez León & M. Jiménez Villalta 2620 (HUTPL 15797!).

Description. Epiphytic herb, caespitose, to 10 cm tall. Roots slender, white, flexuous, 0.5 mm in diameter. Ramicauls suberect, green, 9.1–10.1 cm long, 0.1 cm in diameter, ascending at the base, enclosed by two papery basal sheaths at the base and one below the middle, bracts infundibuliform, upper sheath 11.7–28.7 mm long, glabrous, basal sheath 4.2–10.8 mm long, papulose. Leaves reflexed, sessile, dark green, elliptic to ovate, concave centrally between convex halves, 5.1–6.2 × 2.8–3.5 cm, microscopically papillate, subverrucose, centrally canaliculate, thickly coriaceous, with a navicular concavity behind the flower, base cordate, lobes unequal, sometimes overlapping, margins slightly revolute, apex attenuate. Inflorescence forming successive, multi-flowered coflorescences with a single open flower, subtended by a prostrate, papyraceous spathe, 4.4–5.0 mm long; pseudopeduncle short, ca. 1.6 mm long, floral bract infundibuliform, ca. 3.4 mm long. Pedicel subverrucose, 3.3–4.0 mm long, dilated at the junction with the ovary. Ovary pale yellow with purple papillae, obconic, 1.4–1.9 × 1.3–1.4 mm, coarsely papillose, furrowed. Flowers resupinate or non-resupinate, sepals, petals, and lip pale yellow or rose, profusely covered with chocolate or purple pustules, petals brown at the apex, column whitish yellow, suffused with purple above, clinandrium purple. Sepals papulose-subverrucose abaxially with sparse coarse papillae, dorsal sepal 5 - veined, orbicular elliptic, 5.0–5.3 × 3.9–4.5 mm, slightly convex overall, apex obtuse; synsepal 5–7 - veined, transversely elliptic, 4.3–4.6 × 3.8–4.4 mm, shallow to concave, apex subacute to shortly acuminate. Petals 1 - veined, porrect, oblique, ligulate, slightly falcate, 3.9–4.6 × 0.9–1.2 mm, adaxially slightly canaliculate in the middle, margins flat, apex attenuate, slightly incurved. Lip 3 - veined, cordiform-ovate, carnose, deeply concave, 2.3 × 2.0– 2.1 mm, with a T-shaped cavity and a shallow, purple, inverted V-shaped, bilobed glenion at the base; base subtruncate, with short, obtuse angles; a pair of rounded calli flanking the glenion, margins slightly revolute, apex obtuse. Column complanate, 1.1 × 1.3–1.4 mm, papillose, clinandrium sinuate, rostellar flap 0.3 mm long; stigma apical, transversely elliptic, margins thickened, purple. Anther cap purple, ovate, subcordate, ca. 0.7 × 0.7 mm. Pollinia yellow, obovoid, ca. 0.7 mm long.

Etymology.

Named after Paola Ordóñez Montero, an enthusiastic nature photographer who observed this species.

Distribution and ecology.

Pleurothallis monteroae is known from the western foothills of the central and southern part of the Cordillera del Cóndor in the province of Zamora-Chinchipe, forming part of the ecosystem known as the evergreen lower montane forest on sandstone plateaus of the Cóndor-Kutukú ranges (BsBa 03) (Ministerio de Ambiente del Ecuador 2013), at elevations between 1100 and 1700 m (Fig. 8). In the type locality, individuals of this species grow as epiphytes close to the ground in the understory. Other species of orchids, such as Elleanthus conifer (Rchb. f. & Warsz.) Rchb. f., E. virgatus (Rchb. f.) C. Schweinf., Masdevallia lilacina Königer, M. mendozae Luer, Maxillaria pachyacron Schltr., and Oncidium gayi J. M. H. Shaw, were found sympatrically with P. monteroae. In this area, the local flora is dominated by Baccharis genistelloides (Lam.) Pers., Clusia multiflora Kunth, Semiramisia speciosa (Benth.) Klotzsch, Symbolanthus jasonii J. E. Molina & Struwe and Siphocampylus scandens (Kunth) G. Don. A second locality was found north of the type locality near Tundayme by Raquel Betancourt in 2018 (Figs 7 B, 8). The flowering of this species occurs between March and November.

Conservation assessment.

The species is currently known from four occurrences in two localities in Zamora-Chinchipe Province: three near Cerro Plateado (holotype + two iNaturalist photographic records) and one near Tundayme, ca. 100 km to the north (georeferenced photographic record). The calculated extent of occurrence (EOO) based on these records is 98 km 2, and the area of occupancy (AOO) is 16 km 2.

The known localities are all within an area heavily impacted by large-scale mining concessions, which have already caused severe deforestation and habitat fragmentation in the Cordillera del Cóndor region (Mestanza-Ramón et al. 2022; Mena-Quintana et al. 2025). These threats are ongoing and directly affect habitats required by orchids. Although some populations occur near government-protected areas, such as Cerro Plateado and El Quimi Biological Reserves and El Zarza Wildlife Refuge, these areas do not guarantee effective conservation. Mining concessions overlap with legally protected zones (Roy et al. 2018; Peck et al. 2024), undermining their integrity and exposing the species to severe threats. The proximity of mining concessions to all known localities of Pleurothallis monteroae significantly increases the risk of population decline and potential extinction. Even within protected areas, the presence of concessions indicates weak enforcement of conservation policies.

Although the species may be more widespread but under-collected in southeastern Ecuador, the extremely restricted known distribution (EOO <5,000 km 2; AOO <500 km 2; ≤ 5 locations), combined with the high level of threat and an inferred continuing decline in habitat quality, justifies a preliminary assessment of Endangered (EN) under criteria B 1 ab (iii) + 2 ab (iii), following the precautionary principle recommended by the IUCN.

Additional records.

Ecuador • Zamora-Chinchipe: Nangaritza, 24 April 2024, observation in iNaturalist by Paola Ordóñez Montero, https://www.inaturalist.org/observations/209190380 (Suppl. material 1); Nangaritza, 18 March 2025, observation in iNaturalist by Paola Ordóñez Montero, https://www.inaturalist.org/observations/265967102 (accessed 25 Aug 2025); near Tundayme, 2 November 2018, photo by Raquel Betancourt privately shared with M. Jiménez (reproduced in Fig. 7 B).

Taxonomic notes.

Pleurothallis monteroae is most similar to P. phymatodea in its similarly sized plants (less than 10 cm tall), thickly coriaceous, convex leaves, a suborbicular dorsal sepal, and an ovate, bowl-shaped lip. The new species is distinguished from P. phymatodea by its pale yellow ovary and flowers covered with chocolate to purple papillae (vs. purple-black flowers and ovary with verrucae of the same color), petals with flat margins (vs. involute), and a transversely elliptic synsepal (vs. transversely ovate). Another difference between the two species is the transversely elliptic stigma in the new species (vs. broadly hexagonal in P. phymatodea; Fig. 4 A). P. monteroae is the only species in the group known to have a glenion inside the cavity of the lip.

Pleurothallis monteroae also shows affinities with P. equipedites in its yellowish flowers with purple pustules. However, the new species differs in its smaller dorsal sepal, 5.0–5.3 × 3.9–4.5 mm, and synsepal, 4.3–4.6 × 3.8–4.5 mm (vs. 6.0–7.2 × 5.1–6.0 mm and ca. 6.7 × 6.6 mm, respectively). The most distinctive difference lies in the lip, which in P. monteroae is cordiform-ovate and crateriform, with a T-shaped cavity and a unique bilobed glenion surrounded by two rounded calli (vs. calceiform, with a lanceolate, canaliculate cavity and two elongated, ribbed calli).