Pleurothallis marioi Zambrano & Solano, 2017

Romero, Bosco Javier Zambrano, Solano-Gomez, Rodolfo & Wilson, Mark, 2017, A new species of Pleurothallis (Orchidaceae: Pleurothallidinae) from Southwestern Ecuador: Pleurothallis marioi, Phytotaxa 308 (1), pp. 80-88 : 81-87

Pleurothallis marioi Zambrano & Solano sp. nov. Figs. 1–3 .

Species haec P. artacta Luer similis sed planta pendula , foliis lineari-ensiformibus basi cuneata , sepalo dorsali ovato, petalis oblongosubpanduriformis, labello ovato differt.

Type:— ECUADOR. El Oro: Cantón Marcabelí, near the boundaries with Loja province, 390 m, 21 February 2015, Zambrano B. 1624 (Holotype in QCNE [in spirit], cultivated in Orquiecuador & Gloxinias).

Herb epiphytic, pendent, caespitose, 10–20 cm tall. Roots slender, flexuous, whitish, ca. 1.0 mm diameter. Rhizome abbreviated, cylindrical, ca. 1.0 mm long between stems, with 1–2 nodes, covered by imbricate, chartaceous, persistent sheaths. Stem terete, slightly arching, unifoliate, 10–15 cm long, ca. 1.0 mm in diameter, subtended by 2–3 tubular, imbricate, persistent, chartaceous sheaths, 18–40 mm long, ca. 1.0 mm in diameter. Leaf fleshy, sessile, cuneate at the base, narrowly elliptic-lanceolate when young to linear-ensiform when mature, obtuse, coriaceous, emarginatemucronate at the apex, 50–110 × 5.0–7.0 mm. Inflorescence arising from the apex of the stem, consisting in 1–4 single fasciculate flowers, successively open, enclosed at the base by a spathaceous, conduplicate, persistent, chartaceous bract, 5.0–6.0 × 2.0–3.0 mm; peduncle terete, 4 mm long, 0.5 mm in diameter, covered by a tubular, acute-acuminate, persistent, conduplicate, scarious bract, 3.0–3.5 × 1.0 mm (2.0 mm when extended). Ovary pedicellate, slightly arching, cylindrical, longitudinal sulcate, 3.0–4.0 mm long, 0.7–0.8 mm in diameter. Flowers small, bilabiate, pendulous, the sepals, petals and lip yellow-amber with purple spots, the column light purple, the anther yellow with red spots. Sepals fleshy, densely glandular-papillose on adaxial surface, glabrous abaxially; dorsal sepal fleshy, concave, ovate, subacute to obtuse, 3-nerved, 2.5–3.0 × 1.5–2.5 mm; lateral sepal united up to the apex into a fleshy, deeply concave, broadly ovate, obtuse synsepal, shortly bifid, 4-nerved, 2.3–2.4 (when extended) × 2.3–2.4 mm. Petals fleshy, porrect, slightly concave, oblong-subpanduriform, acute, shortly apiculate, papillose towards the apex, constrained and concave at the middle along the columnar margin, 1-nerved, 1.4–1.6 × 0.6 mm. Lip entire, fleshy, concave, ovate, obtuse, articulate at the base of the column base, glandular-papillose, covered by a translucent viscous-substance on the adaxial surface, 2.0 × 1.4–1.5 mm; the lamina provided with a small, oblanceolate, dark-purple glenion near the base, more three parallel, longitudinal, dark-purple calli, the lateral ones extended from almost the base to the apex, the central one extended on the apical mid, the lateral calli connected among them by a short, transverse, slightly arching callus. Column short, subterete, with an obsolescent foot, 0.7–0.8 mm long and 0.7 mm in diameter, with a clinandrium slightly projecting and covering the anther base; stigma apical, 1-lobed, slightly concave, covered by a viscous substance; rostellum apical, oblong. Anther apical, subglobose-cordiform, glandular-papillose, 0.7–0.8 × 0.5 mm. Pollinarium 0.8–0.9 mm long, formed by 2 pollinia, yellow, narrowly clavate, serous, slightly arched, gradually attenuated at the base, attached to a semilunar viscidium. Capsule not seen.

Distribution and habitat: —Up to now Pleurothallis marioi is only known from southwestern Ecuador, along the border of El Oro and Loja provinces, at 400 m elevation ( Fig. 3 ). The plant grows as an epiphyte on tree branches of Ficus sp. , above thin layer of moss, in environments of transition between the semi-deciduous premontane and evergreen premontane forests.

Phenology: —In culture, P. marioi flowers between June and November.

Eponymy: —The specific epithet is named after Mario Aguilar Atiencie, orchid grower from Marcabelí, Ecuador.

Additional specimens: — ECUADOR. El Oro: Cantón Marcabelí, near the boundaries with Loja province, 390 m, 21 February 2015, Zambrano B. s.n. (isotype in QCNE, cultivated in Orquiecuador & Gloxinias).

Comments: —The most similar species with the new taxon are the Peruvian Pleurothallis arctata and the Venezuelan P. subtilis . Pleurothallis arctata ( Figs. 4A ) can be distinguished from P. marioi by its erect plants (vs. pendent), oblong-lanceolate, basally 2-lobed leaves (vs. linear-ensiform, basally cuneate), oblong-lanceolate dorsal sepal (vs. ovate), longer and falcate-lanceolate petals (2.5 mm vs. 1.6 mm and oblong-subpanduriform), 3-lobed and sagittate lip (vs. entire and ovate), and 2-lobed stigma (vs. 1-lobed). Pleurothallis subtilis ( Figs. 4B ) can be distinguished from P. marioi by its erect plants (vs. pendent), marginally revolute and basally 2-lobed leaves (vs. not revolute, basally cuneate), pale yellow flowers (vs. yellow-amber with purple spots), falcate oblong-lanceolate petals (vs. oblong-subpanduriform), deflexed and round lip (vs. no deflexed and obtuse), slender and arching column (vs. robust and erect), and a prominent foot column (vs. obsolete foot).

Other species similar to P. marioi are the Colombian P. calamifolia and the Ecuadorian P. portillae . Pleurothallis calamifolia can be distinguished by its erect plants (vs. pendent), marginally revolute and basally 2-lobed leaves (vs. not revolute, basally cuneate), orbicular flowers (vs. bilabiate), ovate-triangular petals (vs. oblong-subpanduriform), 3-lobed, subquadrate and conduplicate lip (vs. entire, ovate, slightly concave) and a well develop foot column (vs. obsolete foot). On the other hand, P. portillae ( Figs. 4C ) differs by its revolute sides and basally 2-lobed leaves (vs. not revolute margins, basally cuneate), extended flowers (vs. bilabiate), obovate dorsal sepal (vs. ovate), linearovate petals (vs. oblong-subpanduriform), and triangular-ovate, deflexed, unguiculate lip (vs. ovate, not deflexed, not unguiculate).

The Ecuadorian P. acestrophylla ( Figs. 4D ) has a similar habit (pendent plants, linear, sessile and basally cuneate leaves), but it is distinguished by its elliptic dorsal sepal (vs. ovate), slightly concave synsepal (vs. strongly concave), linear petals (vs. oblong-subpanduriform), oblong-ovate lip (vs. ovate), and column with a 2-lobed stigma (vs. 1-lobed). Finally, the also Ecuadorian P. lemniscifolia , is differentiated by its more or less revolute and basally subcordate leaves (vs. not revolute and basally cuneate), dorsal sepal elliptic (vs. ovate), petals linear-falcate (vs. oblong-subpanduriform), oblong lip (vs. ovate), and 2-lobed stigma (vs. 1-lobed). Table 1 shows a comparative summary between the morphological characters that allow distinguishing the species above mentioned.

Conservation status: —To date this species has not been found in other localities, and it is necessary to consider it as a restricted endemic. Pleurothallis marioi is present in remnant forest disturbed by human activities (Quebrada el Mango), where the populations exhibit low densities (10–15 plants per phorophyte). Furthermore, they are outside of protected areas, so, the conservation of this species would depend on ensuring the quality of its habitat in order to maintain the viability of their populations.

species mentioned in the text ( P. acestrophylla , P. arctata , P. calamifolia , P. lemniscifolia , P. portillae , and P. subtilis ).

Figures

FIGURE 1. Pleurothallis marioi Zambrano & Solano. A. Habit. B. Flower, lateral view. C. Flower dissection. D. Lip, ventral and dorsal view. Drawn by B.J. Zambrano based on the holotype.

FIGURE 2. Photographic plate of Pleurothallis marioi Zambrano & Solano. A. Habit (cultivated plant). B. Apex. C. Flower, lateral view. D. Flower dissection. E. Pedicel, ovary, column, lateral view. F. Column and lip, detail of the dorsal view. G. Lip, detail of the superior view. H. Anther (dorsal and ventral view) and pollinarium. Plate by B.J. Zambrano based on cultivated specimens.

FIGURE 3. Known locality for Pleurothallis marioi in Southwestern Ecuador. Map by B.J. Zambrano.

FIGURE 4. A. Pleurothallis arctata. B. Pleurothallis subtilis. C. Pleurothallis portillae. D. Pleurothallis acestrophylla. Photographs A–C by Ron Parsons, B by Wiel Driessen, D by B.J. Zambrano.