Pleurothallis markgruinii Baquero & M.F. Monteros

Pleurothallis markgruinii Baquero & M.F. Monteros , sp. nov.

This new species is most similar to Pleurothallis gargantua in the large size of the plants (up to 1 m tall) and the large flowers (among the largest in the genus, between 5.6 and 10 cm long) borne at the base of a large (up to 30 cm long) ovate leaf, but it differs from that species in its considerably smaller flowers, 6.1 cm (vs 10.5 cm long when fully extended); the deeply concave, red-brown dorsal sepal (vs slightly concave light green suffused with rose dorsal sepal); the narrower petals, 2 times the length compared with the width, 1.5 × 0.75 cm (vs the broader petals, 1.5 times the length compared with the width, 2 × 1.2 cm); the triangular synsepal with heavily revolute margins (vs ovate synsepal); and the rugulose-verrucose texture of the lip (vs glabrous-rugulose). – Type: Ecuador, Carchi, along the road from El Carmen to Chical, 0°49′39′′N, 78°12′39′′W, 1700 m, 4 iii 2016, Luis E. Baquero LB-3071 (holotype QCNE!). Figures 2, 3A, 4 and 5 GoogleMaps .

Caespitose epiphyte over 1 m tall. Roots slender, 1.5 mm in diameter. Ramicauls stout, erect to suberect, up to 1 m long, with three tight, tubular sheaths borne from the base towards the apex. Leaf spreading, coriaceous, centrally channelled, ovate, acute, acuminate 25–30 × 14–17 cm, base sessile, deeply cordate, basal lobes 3 cm deep, margin entire. Inflorescence a fascicle of one (or few) simultaneous flowers with later successive, resupinate, borne on top of the leaf, flowers produced from a spathaceous bract, c. 2 cm long; peduncle 1–1.5 cm long concealed within the spathe, floral bract 8 mm long; pedicel clavate, straight, c. 1.2 cm long. Flower cream-coloured suffused with brown-red and red-purple, 5.5–6.1 × 2.5–3 cm. Ovary 8 mm long, slightly grooved. Dorsal sepal cream-coloured to yellowish green suffused with red-brown, with darker red-brown veins, glabrous, ovate, obtuse, deeply concave at the basal half, the apical half flat to slightly convex, the margins from slightly revolute at the base to markedly revolute towards the apex, 3.2–3.4 × 2.6–2.8 cm, 19-veined. Lateral sepals red-purple, verrucose, connate into a narrowly triangular, acute synsepal, the margins strongly revolute, 2.4–2.7 × 1.8–2 cm, 16-veined. Petals red-brown, verrucose-papillose, oblong, obtuse, slightly falcate at the truncate base, slightly convex, 1.5 × 0.75 cm, 7-veined. Lip red-brown, orange-yellow towards the base, rugulose-verrucose, transversely obovatespathulate, convex, acute, 8.5 × 9.5 mm, with three swellings at the apex that abruptly turn into two swellings towards the mid-third, separated by a deep sulcus that gradually disappears towards the basal third, the disc with a low, yellow slightly suffused with rose, ovoid, 1 × 1.3 mm callus, the base truncate, hinged at the flattened base of the column-foot. Column pale yellow suffused with rose degrading stripes, stout, semi-terete, 2 × 4 mm. Anther cap yellow suffused with rose, cordiform, glabrous, apical stigma, bilobed. Pollinia 2, ovoid.

Distribution. Cloud forests of northwestern Ecuador, near the limit of Fundación EcoMinga’s Dracula Reserve, around 1700 m in elevation. According to the Ministerio del Ambiente del Ecuador (2013), this ecosystem is classified as lower montane evergreen forest of the western Andes (BSBN04). So far, five populations have been found to the southwest of Cerro Golondrinas; all the plants were found growing epiphytically ( Figure 6).

Habitat and ecology. Flowering in situ between March–April and August. Field observation of dozens of plants over more than 5 years has found this species growing as an epyphite on branches and occasionally tree trunks ( Pleurothallis gargantua has always been found growing on embankments or at the base of trees instead of at the above-ground level on branches or tree trunks).

Pleurothallis markgruinii shares its habitat with other Pleurothallidinae , such as Andinia pilosella (Rchb.f.) Karremans & S.Vieira-Uribe , Platystele alucitae Luer , Platystele pamelae Baquero & Zuchan and Trisetella vittata (Luer) Luer , and other species of orchids, such as Dichaea morrisii Fawc. & Rendle , Miltoniopsis vexillaria (Rchb.f.) God. -Leb. and Telipogon maldonadoensis Dodson & R. Escobar. The forests in which it is found are poorly researched, as evidenced by the recent description of Pleurothallis pamelae Baquero & Zuchan and the number of unidentified taxa awaiting description.

Etymology. Named in memory of Mark Gruin, horticulturist, curator at Zoo America, and benefactor at the Rainforest Trust, who devoted the bulk of his life’s work to protecting nature and supporting budding conservationists.

Proposed IUCN conservation category. The extent of occurrence and area of occupancy are 7.43 and 16 km 2, respectively. Pleurothallis markgruinii is restricted to moist cloud forests where there is an immediate threat from mining activities. Although the species is found in the megadiverse Tropical Andes hotspot in the Ecuadorian Cordillera Occidental biogeographical sector (see Figure 6), it is not in a protected area, and illegal extraction of species is occurring ( Guayasamin et al., 2021; Monteros et al., 2021; Yánez-Muñoz et al., 2021). We suggest that Pleurothallis markgruinii is classified as ‘Critically Endangered’ following the criteria B1b(iii)(iv) IUCN (2019).

Notes. In Table 3, the characteristics of Pleurothallis markgruinii are presented alongside those of other members of the Gargantua group. Besides the much smaller size of the flowers, almost half as long as the flowers of Pleurothallis gargantua , P. markgruinii also differs in the colour and distribution of dark pigmentation of the flowers, magenta with red-brown, the shape of the narrowly triangular synsepal, with strongly revolute margins,

and the deeply concave dorsal sepal, when compared with the red-brown, broadly ovate

Leaves

Shape Ovate, acute, Broadly ovate, Narrowly ovate, Ovate, acute, Ovate, acute, Broadly Ovate-oblong, acuminate, base acute, base acute, base acuminate, base slightly cordate-ovate, acuminate, base deeply cordate deeply cordate cordate deeply cordate acuminate, base obtuse, shortly deeply cordate shallowly cordate acuminate, base deeply cordate

Size (cm) 25–30 × 14–17 25–35 × 18–20 14–18 × 5–7 13–22 × 4–9 32 × 15 15–25 × 10–21 40 × 21

Inflorescence One (or few) One (few) One (few) One (few) Several Several Several simultaneous simultaneous simultaneous simultaneous simultaneous simultaneous simultaneous flowers flowers flowers flowers flowers flowers flowers

Dorsal sepal

Size (mm) 32–34 × 26–28 50–55 × 38–38 30 × 17 26–30 × 17–20 25 × 20 18 × 13 30 × 20

Colour Cream-coloured Light green Pale yellow Light yellow green Purple-brown Rose Dark brown to yellowish green suffused with suffused with suffused with rose rose red-brown

Texture Glabrous Glabrous Glabrous to Glabrous Glabrous Glabrous Glandulosemicroscopically pubescent cellular-glandular externally

Form Ovate, obtuse, Ovate, subacute Ovate Broadly ovate, Broadly ovate, Broadly ovate, Broadly ovatemargins revolute subacute to subacute to obtuse lanceolate, obtuse obtuse acuminate

Veins 19-veined 19-veined 13-veined (faint) Multiveined Multiveined 15-veined Multiveined

Synsepal

Size (mm) 24–27 × 18–20 45–50 × 25 30 × 15 21–30 × 15–16 25 × 15 16 × 14 25 × 17

Colour Red-purple Red-brown except Light rose Light yellow- Purple-brown Dark rose Dark brown green crescent at green, suffused base with rose

Texture Verrucose Covered by Glabrous to Glabrous Spiculate- Glabrous Glanduloseminute blackish microscopically pubescent above externally, pubescent red papillae cellular-glandular the middle minutely papillose externally within

Form Narrowly Ovate, subacute Ovate, acute Ovate, subacute Ovate, subacute Cordate-ovate, Broadly ovate-

triangular, acute, obtuse lanceolate, apex margins strongly bidentate revolute

Cordate-ovate, acute, base deeply cordate

25–30 × 12–16

Several simultaneous flowers

28–35 × 28–30 Dark purple

Glabrous

Broadly ovoid, obtuse

13- to 15-veined

27–32 × 18–20 Dark purple

Glabrous

Ovate, subacute synsepal and a light green suffused with rose and shallowly concave dorsal sepal of the flowers of P. gargantua . Another substantial difference is the narrower petals with 7 nerves vs the 11-nerved and rounder and broader petals of Pleurothallis gargantua ( Figures 2–4). Pleurothallis markgruinii has the third largest flower of the Gargantua group of species, after P. gargantua and P. teaguei .

Considering that Pleurothallis gargantua , Pleurothallis aff. imperialis and P. markgruinii grow in similar cloud-forest ecosystems, it is possible that there may be different pollinators for each species. This would explain the genetic isolation between the three species, although more pollinator–plant studies are needed to confirm this. It is striking that no overlapping populations have been found among the three species, whose populations grow very close to each other and in very similar ecosystems (see Figure 6). After analysing many flowers from individual plants, no intermediate forms of Pleurothallis between P. gargantua and P. markgruinii have been found.

Additional specimens examined. Paratype: EcUADOR. Carchi, at the base of Cerro Golondrinas, 0°52′48′′N, 78°11′34′′W, 1729 m, 7 viii 2022, Marco F. Monteros MFM 238 (QCNE!).