Pleurothallis tinajillensis M.M.Jiménez, H. Garzón & Vélez-Abarca, 2023

Jiménez, Marco M., Vélez-Abarca, Leisberth, Mashendo-Jimbicti, Viviana, Garzón-Suárez, Henry X., Monteros, Marco F. & Wilson, Mark, 2023, Five new species of Pleurothallis (Orchidaceae: Pleurothallidinae) in subsection Macrophyllae-Fasciculatae from Southeastern Ecuador, Phytotaxa 607 (3), pp. 161-181 : 173-178

5. Pleurothallis tinajillensis M.M.Jiménez, H. Garzón & Vélez-Abarca , sp. nov. ( Figures 11–12 )

Type: — ECUADOR. Morona Santiago: Municipal Conservation Ecological Area Tinajillas – Río Gualaceño , between Limón and Gualaceo , 3°00’45.10’’ S, 78°31’29.06” W, 26 May 2022, 2336 m, M. Jiménez & H. Garzón 1410 (holotype: HUTPL 14634 !) .

Similar to Pleurothallis ruberrima , from which it differs by its lanceolate, attenuate leaves (vs. narrowly ovate, acute), flowers lying on the leaf surface (vs. dangling over the sides of the leaf), elliptic-ovate dorsal sepal (vs. narrowly ovate), the base of the petals unlobed, separated from each other (vs. with an obtuse lobe, very close to each other), the lip triangular-ovate, sulcate without a callus (vs. broadly ovate, convex with a rounded callus).

Description:— Plant epiphytic, up to 23 cm tall, roots slender, flexuous, 0.6–0.9 mm in diameter. Ramicauls slender, suberect, terete, 13.5–21.6 long and 1.3–1.6 mm in diameter, enclosed by papyraceous, tubular sheaths, upper sheath 33.4–37.2 mm long, basal sheath 22.6–24.8 mm long. Leaves green adaxially, suffused with purple abaxially, lanceolate, attenuate, dull, centrally channeled, 9.0–13.0 × 2.5–3.2 cm, concave with slightly raised lateral nerves, base cordate, margins purple. Inflorescence a fascicle of successive flowers produced from a reclined, papyraceous, spathaceous bract, 14.0– 17.7 mm long; peduncle short, 3.6 mm long, floral bract infundibuliform, 8.4 mm long; pedicel very long, verrucose, dilated at the junction with the ovary, 12.1 mm long. Flowers glossy, delicate, lying against the leaf, sepals and petals pale garnet green toward the ends, with purple minute pubescence. Dorsal sepal elliptic-ovate, 7-veined, 8.0 × 11.7 mm, convex, margins revolute. Lateral sepals united into an ovate, 6-veined, slightly concave, obtuse, 14.0 × 8.2 mm synsepal. Petals narrowly oblong, slightly falcate, lanceolate, 3-veined, ribbed at the midvein, 10.1–10.4 × 1.9–2.0 mm, base thickened, whitish, verrucose, recurved, separated at the upper margin from the other petal, apex acute, minutely incurved. Lip greenish white, tan and purple to the apex, triangular-ovate, 3-veined, verrucose-papillose, 4.3 × 3.4 mm, adaxially sulcate in the middle with two lateral depressions at each side, margins minutely erose, base truncate with a small glenion, apex apiculate, center of the base of the lip without a callus. Column stout, white, complanate, papillose, 3.0 mm long including the rostellar flap, 1.7 × 1.2 mm, apex flared, thickened. Anther narrowly obovate, whitish brown, papillose, 1.1 mm long, bilobed at the base, pollinia 2, yellow, clavate, 1.1 mm long. Ovary subverrucose, subclavate, almost straight, 5.1 × 1.3 mm.

Distribution and ecology: —Up to now Pleurothallis tinajillensis is only known from the type locality on the steep slopes into the AECMTRG in the Morona Santiago Province ( Figure 3 ). The species grows at the foot of the hills in the montane rainforest at around 2300 m in elevation, on the Eastern slope of the Cordillera Oriental of the Andes. It grows on tree trunks, together with other orchid species such as Elleanthus vernicosus Garay (1978: 105) , Maxillaria meridensis Lindley (1846: 19) , Oncidium cruentoides Chase & Williams (2008: 24) , Pleurothallis eccentrica Luer & Hirtz (1988: 140) and Pleurothallis amplectens Luer (1980: 73) . The local vegetation is characterized by Cecropia andina ( Cuatrecasas 1945: 286) , Oreopanax andreanus Marchal (1880: 90) , Andesanthus lepidotus and Weinmannia fagaroides Kunth (1823: 54–55) .

Etymology: —Named after Tinajillas, which is the Municipal Conservation Ecological Area Tinajillas–Río Gualaceño (AECMTRG), where the type locality is found. It is an important local protected area in southeastern Ecuador, home to a considerable area of natural vegetation that includes montane and premontane forest ecosystems.

Taxonomic discussion: — Pleurothallis tinajillensis is most similar to P. ruberrima but it is distinguished by its smaller plants, up to 23 cm tall (vs. 35 cm), concave, centrally channeled, suffused with purple at the abaxial surface of the leaf (vs. convex, sulcate, green at the abaxial surface of the leaf), shorter pedicel (12 mm vs. 20–60 mm long), minutely pubescent sepals and petals (vs. glabrous), shorter dorsal sepal (11.7 vs. 15–23 mm long), extended horizontally petals (vs. reflexed), pulvinate, apiculate, basally truncate lip (vs. convex, broadly obtuse to rounded, basally subcordate), and whitish, complanate column (vs. green and white or purple, ancipitous) with a longer rostellum (1.2 mm long vs. 0.4 mm).

Conservation status: —This species has not been reported within the Ecuadorian National System of Protected Areas but the type locality is located within the AECMTRG, an area of ~32,928 hectares protected since 2002. Pleurothallis tinajillensis appears to have a very restricted distribution and may be endemic to the province of Morona Santiago. Additional data is required about distribution and abundance of this species before a valid conservation assessment can be made.

Figures

FIGURE 3. Distribution map of Pleurothallis kashi-menkakarai (black circle), P. lapoi (black square), P. marioandresavilae (black star), P. sabanillae (black cross), P. saueri (also black square), P. tinajillensis (black diamond) in Ecuador and mining threats (red squares). Map by Henry X. Garzón.

FIGURE 11. Pleurothallis tinajillensis. A. Habit. B. Flower. C. Dissected perianth. D. Ovary, column and lip in lateral view. E. Lip adaxial and abaxial views. Illustration by L. Vélez-Abarca based on the type.

FIGURE 12. Flower and frontal view of the lip. A. Pleurothallis ruberrima B. P. tinajillensis. Close-up of the lips and columns. C. Pleurothallis ruberrima. D. P. tinajillensis. Elaborated by Henry Garzón from photos by A. Henry X. Garzón based on a in situ specimen and B. Marco M. Jiménez based on the type.