Platystele apoloae Zambrano & Solano, 2018

Romero, Bosco Javier Zambrano, Solano, Rodolfo & Cornejo, Xavier, 2018, Platystele apoloae (Orchidaceae: Pleurothallidinae), a new species from Southwestern Ecuador, Phytotaxa 372 (1), pp. 88-96 : 89-94

Platystele apoloae Zambrano & Solano sp. nov. Figs. 1–4 .

Species haec P. cornejoi Luer similis sed petalis elliptico-lanceolatis, marginibus erosis, labello ovato glandulari-papilloso differt.

Type:— ECUADOR. El Oro: Cantón Marcabelí , near the boundaries with Loja province, 390 m, 21 February 2015, B. Zambrano 1626 (Holotype in QCNE; isotype in QCNE [in spirit]) .

Epiphytic, densely caespitose herb, ca. 1.0 cm tall without inflorescence. Roots slender, flexuous, whitish, ca. 0.6 mm diameter. Rhizome cylindrical, ca. 0.1 mm long between stems, covered by imbricate, chartaceous, persistent sheaths. Stem terete, unifoliate, 1.5–3.5 mm long, ca. 0.3–0.4 mm in diameter, subtended by 2–3 tubular, imbricate, persistent, chartaceous sheaths, 1.0–2.0 mm long, ca. 0.4 mm in diameter. Leaf 4.0–7.0 × 3.0–5.0 mm, fleshy, sessile, green or green with purple spots, cuneate at the base, ovate when young to oblong-obovate when mature, obtuse, emarginated and mucronate at the apex, marginated, abruptly attenuate at its base into a short petiole. Inflorescence arising from the annulus of the stem, erect, a successively flowered raceme, up to 10 cm long, enclosed at the base by a spathaceous, conduplicate, persistent, chartaceous bract, ca. 0.5–0.6 mm long, peduncle longer than the leaf, 10–15 mm long, covered near the base by 2–3, tubular, imbricate, chartaceous, persistent bracts, 0.2–0.3 mm long; rachis flexuous, progressively elongating at the apex with the development of new flowers; pedicel 1.5–3.0 mm, 0.1 mm in diameter, adjacent pedicels separated from each other by 1.5–3.0 mm; floral bract, acute, persistent, scarious, 0.4–0.7 × 0.3 mm (0.6 mm when expanded). Flowers small, extended, stellate, the sepals and petals light-yellow or yellow with purple spots, lip purple, anther yellow. Sepals membranous, translucent, 1-nerved, glabrous; dorsal sepal concave, oblong-ovate, acute, 1.3–1.7 × 0.9–1.0 mm; lateral sepals united almost 1/3 at their base, slightly convex, ovate, slightly oblique, acute, 1-nerved, 1.3–1.6 × 0.9–1.0 mm. Petals membranous, elliptic-lanceolate, oblique, acuminate, minutely erose along the margins, 1-nerved, 1.2–1.6 × 0.5–0.6 mm. Lip entire, ovate from a truncate base, obtuse, apically incurved, glandular-papillose, articulated at the base of the column, 1.2–1.4 × 0.9–1.0 mm; the lamina provided with a small, rounded callus near the base. Ovary obconic, longitudinal sulcate, ca. 0.4 mm long, 0.3–0.4 mm in diameter. Column short, subterete, apically cucullate, with an obsolescent foot, glandular-papillose on the adaxial surface, ca. 0.5 mm long, with a clinandrium slightly projecting and covering the anther base. Stigma apical, 2-lobed, each lobe concave and covered by a viscous substance; rostellum apical, laminar.Anther apical, subglobose, glandular-papillose, ca. 0.1 × 0.1 mm. Pollinarium ca. 0.1 mm long, with 2 yellow, narrowly clavate, serous pollinia, attached to a tiny drop of viscidium. Capsule not seen.

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

Phenology: —In culture, Platystele apoloae blooms apparently throughout the year.

Eponymy: —The specific epithet is named after Carmen Apolo Bustamante, orchid grower from Marcabelí (El Oro), Ecuador.

Additional specimens: — ECUADOR. El Oro: Cantón Marcabelí, near the boundaries with Loja province, 390 m, 21 February 2015, B. Zambrano s.n. (QCNE, cultivated in Orquiecuador & Gloxinias). Loja: Cantón Paltas, near the boundaries with El Oro province, 400 m, 21 February 2015, B. Zambrano s.n. (QCNE, cultivated in Orquiecuador & Gloxinias).

Comments: —The most similar species with the new taxon is the Ecuadorian Platystele cornejoi which can be distinguished from P. apoloae by its shorter inflorescence (less 4.0 cm vs. up to 10 cm), shorter pedicels (1.0– 1.5 mm vs. 1.5–3.0 mm), smaller sepals with an obtuse apex (1.0 mm vs. 1.3–1.7 mm, acute), smaller, not oblique, acute, marginally entire petals (0.8 mm vs. 1.2–1.6 mm, oblique, acuminate, marginally erose), yellow or yellow and red stained lip provided with a triangular callus (vs. purple, with a rounded callus), yellow-green and concolor column (vs. light yellow with purple on the stigmatic lobes) ( Luer 2010). On the other hand, P. cornejoi is only known to inhabit the interior of mangroves at northwestern Ecuador (REMACAM, province of Esmeraldas) ( Fig. 5 ), and the adjacent mangroves of southwestern Colombia (Campana, Department of Nariño), in the wet forest life zone. It may also occur nearby in the terra firme forest of Choco. Since this species has not been reported for southwestern Ecuador and Peru ( Cornejo 2014), and the fact that P. apoloae occurs at the interior the Amotape-Huancabamba zone ( Weigend 2004), the geographic disjunction, between the northwestern populations of it and that from P. apoloae and the distribution patterns of both species in two distinctive biogeographic areas also support the recognition of P. apoloae as a different taxa.

Other species similar to P. apoloae are the Central American, P. carl-lueriana , P. catiensis , P. pedicellaris , P. propinqua , and P. ovalifolia . Platystele carl-lueriana can be distinguished by its narrowly elliptic leaves (vs. oblong-obovate), shorter inflorescence (less 2.2 cm vs. up to 10 cm), ovate to lanceolate and acute-acuminate dorsal sepal (vs. oblong-ovate, acute), and narrowly ovate lip with a slightly concave callus (vs. ovate, with a rounded callus) ( Karremans & Bogarín 2017). Platystele catiensis , is different by its shorter inflorescence (1.3 cm vs. up to 10 cm), longer and lanceolate-elliptic dorsal sepal (2.3 mm vs. 1.3–1.7 mm, oblong-obovate), marginally glandular-papillose petals (vs. marginally erose), ovate-elliptic and shortly acuminate lip (vs. ovate, obtuse), and a slightly concave callus (vs. rounded) ( Fernández et al. 2014). Platystele pedicellaris differs by its narrowly elliptic leaves (vs. oblong-obovate), shorter inflorescence (1.5 cm vs. up to 10 cm), longer and ovate dorsal sepal (6.0 mm vs. 1.7 mm, oblong-obovate), elliptic-obovate and marginally ciliate petals (vs. elliptic-lanceolate, marginally erose), and a slightly concave callus (vs. rounded) ( Schlechter 1912, Garay 1974, Luer 1990). Platystele propinqua differs by having elliptical-obovate leaves (vs. oblong-obovate), longer, ovate and acute-acuminate dorsal sepal (5.5 mm vs. 1.3–1.7 mm, oblong-ovate, acute), longer, narrowly ovate and marginally entire petals (5.0 mm vs. 1.6 mm, elliptic-lanceolate, marginally erose), and an acute-acuminate lip with a broad callus (vs. obtuse, with a rounded callus) ( Ames 1923, Garay 1968, Luer 1990).

Finally the Caribbean and the north South American Platystele ovalifolia can be distinguished from P. apoloae by its rhizomatous habit (vs. caespitous), elliptic to suborbicular leaves (vs. oblong-obovate), shorter inflorescence (1.0 cm vs. up to 10 cm), elliptic-oblong, marginally entire petals (vs. elliptic-lanceolate, marginally erose), and lip with a minute concave callus (vs. rounded callus) ( Focke 1849, Luer 1990). Table 1 present a summary of the differences among the species mentioned above.

species mentioned in the text ( P. carl-lueriana , P. catiensis , P. cornejoi , P. ovalifolia , P. pedicellaris and P. propinqua ).

Conservation status: —To date this species has not been found in other localities, and it is necessary to consider it as a restricted endemic. Platystele apoloae is present in remnant forest disturbed by human activities (Quebrada El Mango), where the populations exhibit low densities (5–10 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.

Figures

FIGURE 1. Platystele apoloae Zambrano & Solano. A. Habit. B. Flower, frontal view. C. Flower dissection. D. Pedicel, ovary, column, and lip, lateral view. Drawn by B.J. Zambrano based on the holotype.

FIGURE 2. Platystele apoloae Zambrano & Solano.A. Habit (cultivated plant). B. Apex of a leaf. C. Flower, frontal view. D. Segments of the inflorescence with pedicel in detail. E. Flower, pedicel, ovary, lateral view. F. Detail of the column and anther, frontal view. G. Detail of the lip, frontal view. H. Detail of the petal. Plate by B.J. Zambrano based on cultivated specimens.

FIGURE 3. Known localities for Platystele apoloae (z) and Platystele cornejoi (Ì) in Ecuador. Map by B.J. Zambrano.

FIGURE 4. A. Pictures from three plants of Platystele apoloae (B. Zambrano 1626 (Holotype), s.n. (El Oro), s.n. (Loja)). Photographs by B.J. Zambrano.

FIGURE 5. A. Pictures from plants of Platystele cornejoi (X. Cornejo & Cangá 8137). Photographs by X. Cornejo.