Pleurothallis lapoi M.M.Jiménez & 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 : 166-168

2. Pleurothallis lapoi M.M.Jiménez & Vélez-Abarca , sp. nov. ( Figures. 4–5 )

Type:— ECUADOR. Zamora Chinchipe: Near El Pangui , 781253.08 E, 9597652.43 S, 1560 m, M. Jiménez 1424 (holotype: HUTPL 14640 !)

Similar to Pleurothallis erythrium Luer (1978: 386) from which differs by its ovate-triangular dorsal sepal (vs. oblong-ovate), the oblong-triangular petals (vs. narrowly linear-oblong) and the yellow, triangular-ovate and shallow lip (vs. red-purple, oblong-ovate, rounded at the apex and convex) with two calli (vs. concave at the end).

Description:— Plant epiphytic, up to 19 cm tall, roots slender, white, flexuous, 0.6–1.0 mm in diameter. Ramicauls slender, suberect, terete, 14.0–16.6 long and 0.1 cm in diameter, enclosed by papyraceous, tubular sheaths, upper sheath 24.6–31.0 mm long, basal sheath 12.6–15.7 mm long. Leaves green, slightly falcate to falcate, ovate, shortly attenuate, glossy, centrally channeled, 5.1–6.3 × 2.1–2.6 cm, base cordate, margins revolute. Inflorescence a fascicle of successive flowers produced from a reclined, papyraceous, spathaceous bract, 6.6–8.0 mm long; peduncle 6.3–6.8 mm long, floral bract infundibuliform, 3.6–4.0 mm long; pedicel verrucose, dilated at the junction with the ovary, 6.2 mm long. Flowers glossy, sepals papillose, subverrucose below the apical third. Dorsal sepal purple, ovate-triangular, 3-veined, 6.1–6.6 × 3.2 mm, acute, shallow, margins slightly involute, callose at the base. Lateral sepals united into an ovate, purple infused with yellow to the apex and veins, 4-veined, shallow, acute, 5.5–5.7 × 3.7 mm synsepal, apex minutely incurved. Petals purple with yellow borders, oblong-triangular, deflexed, lanceolate, 1- veined, microscopically papillose-verruculose, acute, carinate abaxially at the midvein, 3.8–3.9 × 0.7–0.8 mm, margin minutely erose. Lip dark yellow, tan and purple to the apex, triangular-ovate, 3-veined, shallow, verrucose-papillose, 2.6–2.9 × 2.0 mm, with a Y-shaped cream-colored depression and two triangular calli around the glenion that reaches up to the apical third, margins minutely erose, incurved, base cordate with a small, ovate glenion, apex acute, center of the base of the lip with two calli. Column stout, pale green suffused with purple dorsally and to the stigmatic margin, complanate, papillose, 1.2–1.6 × 1.1 mm, stigma reniform, rostellar flap minute, 0.1 mm long, column foot 0.6 mm long, with longer papillae. Anther broadly ovate, microscopically papillose, orange-purple, 0.5 mm long. Pollinarium with 2, ovoid, yellow pollinia, 0.4 mm long. Ovary green-purple, lightly verrucose, subterete, slightly arcuate, 3.8–4.0 × 0.9 mm.

Distribution and ecology: — Pleurothallis lapoi was found in southeastern Ecuador growing in an evergreen lower montane forest of the eastern Andes of southern Ecuador, Zamora Chinchipe province, El Pangui canton ( Figure 3 ). Populations have been observed within the Cayamatza micro-basin at 1560 m elevation. This area is characterized by very steep slopes with rapidly accelerating deforestation due to expansion of the agricultural frontier. These forests are dominated by Erythrina amazonica Krukoff (1939: 270) (Fabaceae) , Cedrelinga cateniformis ( Ducke 1915: 17) Ducke (1922: 70) (Fabaceae) , Jacaranda copaia ( Aublet 1775: 650) Don (1823: 267) (Bignoniaceae) and Inga sp. (Fabaceae) trees. In this forest it is found on tree trunks and branches of the lower canopy stratum, together with other orchid species such as Masdevallia don-quijote Luer & Andreetta (1985: 63) , Myoxanthus exasperatus ( Lindley 1859: 15) Luer (1982: 36) , Pleurothallis saueri ( Luer 2012: 355) Shaw (2016: 39) and Stelis spp.

Etymology: —Named after Lester Lapo, outstanding orchid grower from El Pangui, Zamora Chinchipe Province, who discovered the species.

Taxonomic discussion: —The new species is distinguished from other species of Pleurothallis subsect. Macrophyllae-Fasciculatae by its small purple flowers, acute sepals, and verrucose-papillose, triangular-ovate, yellow lip. It is most similar to Pleurothallis erythrium . Pleurothallis lapoi can be distinguished from P. erythrium by its larger plants (up to 19 vs. 12 cm tall), convex leaves with revolute margins (vs. concave with flat margins) and the flowers with acute, verrucose sepals and lip (vs. papillose, subacute).

Conservation status: — Pleurothallis lapoi has not been found in any formally protected area in Ecuador. So far, no more than five individuals have been sighted within the Cayamatza micro-basin. Deforestation is ongoing in the area for the establishment of cattle pastures and subsistence crops by local residents.

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 4. Pleurothallis lapoi. 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 5. Floral structure comparison of Pleurothallis lapoi (above) and P. erythrium (down). A–D. Flower, lip and sepals of P. lapoi based on the type. E–G. Flower, lip and sepals of P. erythrium based on M. Jiménez 318. Elaborated by L. Vélez-Abarca from photos by Marco M. Jiménez.