Pleurothallis bilobulata M.M.Jiménez, Ocupa & Vélez-Abarca, 2021

Jiménez, Marco M., Horna, Luis Ocupa & Vélez-Abarca, Leisberth, 2021, A new species of Pleurothallis (Orchidaceae: Pleurothallidinae) from Zamora in the Province of Zamora Chinchipe, Ecuador, Phytotaxa 518 (1), pp. 79-86 : 79-85

Pleurothallis bilobulata M.M.Jiménez, Ocupa & Vélez-Abarca , sp. nov. Figs. 1–6 .

Type:— ECUADOR. Zamora Chinchipe: Flank of the Eastern Cordillera of the Andes , near Zamora , 4°05’23.68” S; 78°56’30.68” W, 992 m, 1 Aug 2019, M . Jiménez 713 (holotype: HUTPL) .

Similar to P. lanigera Luer & Hirtz in Luer (1988: 146) from which it is distinguished by the narrowly ovate leaves (vs. cordate-ovate), the straight, subverrucose ovary (vs. curved, minutely papillose), the broadly elliptic dorsal sepal (vs. broadly ovate), the shortly acuminate, narrowly lanceolate, papillose-verrucose, 1-veined petals (vs. acute, elliptic, pubescent, 3- veined) and the lip with a basal, bilobed glenion (vs. lip with a central, circular glenion).

Plant epiphytic, up to 16 cm tall; roots slender, flexuous, 0.6–1.3 mm in diameter. Ramicauls slender, suberect, terete, 45–112 × 0.8–1.2 mm, enclosed by papyraceous, tubular sheaths, upper sheath 12.9–18.9 mm long, basal sheath 6.2–7.7 mm long. Leaves deflexed, coriaceous, microscopically papillate, narrowly ovate, 4.6–7.5 × 1.4–2.2 cm, acute, shortly acuminate, sessile, cordate at the base, lobes unequal. Inflorescence a fascicle of successive flowers produced from a suberect, scabrous spathaceous bract, 4.8–7.4 mm long; floral bract infundibuliform, 4.4–4.6 mm long; pedicel subflexuous, 2.4–3.5 mm long; ovary subverrucose, straight, 2.6–3.0 × 1.0 mm. Flowers resupinate or not; dorsal sepal chestnut, broadly elliptic, acute, 6.9–8.0 × 4.1–4.3 mm, 5–veined, pubescent-verruculose, glossy externally; the lateral sepals fused in an ovoid synsepal, burgundy-chestnut, acute, 5.7–6.5 × 3.9–4.1 mm, concave centrally, 4-veined, verruculose. Petals burgundy to chestnut, narrowly lanceolate, shortly acuminate, 4.7–5.3 × 1.0– 1.2 mm, 1-veined, microscopically papillose-verruculose, margin shortly dentate-ciliate, constricted and oblique at the base. Lip burgundy chestnut, stout, thick, ovate, obtuse, 2.6–2.8 × 2.2–2.3 mm, diffusely cellular verrucose, convex, slightly concave at the apex and to either side of the glenion; the base subtruncate, hinged to the column-foot, with short, obtuse angles and a large, deep, obovoid, bilobed glenion occupying the basal third of the lip. Column stout, pale green suffused with purple, 1.3–1.4 × 1.5–1.7 mm, papillose, stigma bilobed, ventral, reniform, minutely ciliate on margins, rostellar flap 0.4 mm long. Anther narrowly deltoid, white, apical, 0.6 mm long, bilobed at the base. Pollinarium with 2 narrowly obovoid, yellow pollinia, 0.6 mm long, brought together by a drop-like viscidium.

Etymology: —From the Latin bi, “two”, and lobulatus, “small lobes”, referring to two lobes in the glenion of the lip.

Distribution and habitat: — Pleurothallis bilobulata is only known from the type locality type on the steep hillsides near Zamora, in the Zamora Chinchipe province ( Fig. 6 ). The species grows on hill-tops in the premontane rainforest at around 900 m in elevation, on the Eastern slope of the Cordillera Oriental of the Andes. It is a rare species that grows in primary forests, on understory lianas, together with other orchid species such as Elleanthus blatteus Garay (1978: 71) , E. oliganthus ( Poeppig & Endlicher 1836: 33) Reichenbach (1863: 481) , Masdevallia strobelii Sweet & Garay (1966: 377) , Peristeria ephippium Reichenbach (1883: 198) , Pleurothallis lanigera . The local flora is dominated by Hedyosmum cuatrecazanum Occhioni (1954: 23) , Pleroma ochypetalum ( Ruiz & Pavón 1802: 86) Don (1823: 295) , Piptocoma discolor ( Kunth 1818: 35–36) Pruski (1996: 97) , Ladenbergia oblongifolia (Humboldt ex Mutis 1793: 465) Andersson (1994: 19) , Lacistema aggregatum ( Bergius 1772: 131–132) Rusby (1907: 447) and Miconia albicans ( Swartz 1788: 70) Steudel (1841: 139) . The species may be considered as threatened given the destruction of the habitat where the only individuals have been found. It is not currently known to occur in any protected areas.

Comments: —The new species is reminiscent of P. lanigera ( Fig. 3B ) in the pubescent sepals that are similar in length to the petals and the papillose lip. Both occur in southeastern Ecuador and may be found growing in sympatry at around 1000 m near Zamora. The lack of intermediate specimens suggests they are reproductively isolated and don’t hybridize. Pleurothallis bilobulata can be distinguished from P. lanigera by the narrowly ovate leaves, the straight, subverrucose ovary, the broadly elliptic dorsal sepal, the shortly acuminate, narrowly lanceolate, papillose-verrucose, 1-veined petals and the lip with a basal, bilobed glenion ( Figs. 4 , 5 ).

The bilobed glenion is an uncommon feature among the members of Pleurothallis subsect. Macrophyllae-Fasciculatae. It is only known to occur in the distantly related Pleurothallis rhodoglossa Schlechter (1922: 22) and P. nangaritzae M.M.Jiménez, Tobar & Mark Wilson in Wilson et al. (2016: 358), and the closely related P. cardiostola Reichenbach (1854: 26) (Wilson, pers. comm.).

Figures

FIGURE 1. Line drawing of P. bilobulata. A. Habit B. Flower C. Dissected perianth D. Column, lip and ovary, lateral view. E. Lip, adaxial and abaxial view. F. Anther cap and pollinarium. By L. Vélez-Abarca based on the the plant that served as type.

FIGURE 2. Lankester Composite Dissection Plate (LCDP) of P. bilobulata. A. Habit B. Flower C. Dissected perianth. D. Close-up of the shortly dentate-ciliate petal. E. Column, lip and ovary, lateral view. F. Lip, adaxial view. G. Close up of the diffusely cellular verrucose lip. H. Anther cap and pollinarium. By L. Ocupa Horna and M.M. Jiménez based on the the plant that served as type.

FIGURE 3. Detail of the flower. A. Pleurothallis bilobulata. B. Pleurothallis lanigera. Photos by M. Jiménez.

FIGURE 4. Lip, column and ovary of P. bilobulata (left) and P. lanigera (right). A. Frontal view of the lip. B. Lateral view of the column, lip and ovary. Photos by M. Jiménez.

FIGURE 5. Column, anther and pollinarium of P. bilobulata (left) and P. lanigera (right). A. Frontal view of the column. B. Anther and pollinarium. Photos by M. Jiménez.

FIGURE 6. Distribution map of Pleurothallis bilobulata. Prepared by Eugenio Restrepo using ArcGIS.