Pleurothallis flavomarginata A.Doucette, H.Medina, & J.Portilla, 2017

Doucette, Alfonso, Portilla, Jose, Medina, Hugo & Cameron, Kenneth M., 2017, A new species of Pleurothallis (Orchidaceae: Pleurothallidinae) from Ecuador, Phytotaxa 295 (2), pp. 194-198 : 194-197

Pleurothallis flavomarginata A.Doucette, H.Medina, & J.Portilla sp. nov. ( Figs. 1–2 )

Type:— ECUADOR. Lita: El Cristal, 800 m, 9 November 2016, Ivan Portilla s.n. (holotype: QCNE).

Diagnosis:— Pleurothallis flavomarginata is most similar to the Panamanian Pleurothallis allenii L.O.Williams in Allen et al. (1940: 275), but differs from it by its longer stem (97–141 mm vs. 35–50 mm), broader leaf (19–20 mm vs. 5–8 mm), concave and apically incurved dorsal sepal (vs. slightly concave and apically straight), long acuminate and incurved petals (vs. acute and straight), and long acuminate and apically incurved lip with triangular-uncinate lateral lobes (vs. acute, apically straight with oblong lateral lobes).

Epiphytic, caespitose herbs, roots 0.9 mm in diam. Stems unifloliate, 96.9–141.0 mm long, 1.1–1.4 mm in diam., enveloped by 2–3 tubular, adpressed, papery sheaths, 15.7–31.0 mm long, 1.1–1.4 mm in diam. Leaves erect, coriaceous, broadly elliptic, acute, tridenticulate at the apex, 71.0–80.0 × 18.8–20.3 mm, attenuated towards the base into a short channeled petiole. Inflorescence formed by a fascicle of solitary flowers, successively open; peduncle filiform, glabrous, persistent, 14.2–21.0 mm long, 0.3–0.9 mm in diam.; bracts tubular, membranous 3.1–4.6 × 0.9–1.1 mm; pedicel terete, glabrous 3.2–3.7 × 0.5–0.7 mm; ovary glabrous, 6-sulcate, 3.6–3.9 mm long, 0.9–1.0 mm in diam.; dorsal sepal purple with a yellow margins, concave, ovate, acute, acuminate, 11.1 × 2.8 mm; lateral sepals purple with a yellow margins and cream along the line of connation, fused for all their length into a slightly concave, narrowly ovate, acute synsepal, 11.5–11.7 × 3.6 mm, channeled near the base; petals purple with a yellow margin, obliquely ovate, acute, acuminate, the apex incurved, 10.1 × 1.5 mm; lip purple, yellowish at the base with a low smooth callus, 3-lobed, triangular, long acuminate, incurved at the apex, adaxially glandular-papillose, 3.6 × 1.4 mm unexpanded; lateral lobes near the base, triangular-uncinate, held freely around the column; column purple, subterete 1.4–1.6 × 0.8 mm; stigma apical, bilobed, greenish; anther apical.

Etymology: —From the Latin flavum, yellow and marginatus (adjective for margin). The name refers to the yellow margin of the sepals and petals of the species.

Notes:— Presently the new species is only reported from Ecuador and given the narrow distribution of other species of attributable to Pleurothallis subgen. Pleurothallis sect. Acroniae ser. Amphygiae we expect Pleurothallis flavomarginata to occupy a similarly narrow distribution in cloud forest habitats of the Andean region. Species attributable to the series are distributed across Colombia (12 spp.), Ecuador (13 spp.), Venezuela (one sp.), and Panama (four spp.). No species are known to have a range across both Central and South America with only a few species reported to occur in both Ecuador and Colombia. The new species is free flowering in cultivation. The phenology of the new species in nature is unknown.

Despite the atypical leaf morphology, Pleurothallis flavomarginata is best accommodated in Pleurothallis subgen. Pleurothallis sect. Acroniae ser. Amphygiae given the morphological traits it shares with the series. The series Amphygiae is “characterized by a single-flowered, long-pedunculate inflorescence” and a “lip triangular and acute with the basal angles sometimes lobe-like” ( Luer 1998). The monophyly of the series remains to be established, however, we follow Luer’s (1998) circumscription of the group given the lack of an alternative, formalized system of classification backed by the results of a molecular phylogenetic analysis.

The new species described here is easily distinguished from all species attributable to the series based on the petiolate (vs. sessile, subcordate/cordate) leaves and the coloration of the flowers, which lends to the species’ striking resemblance to the Panamanian Pleurothallis allenii . Despite the similar coloration, the new species can be distinguished from P. allenii by the longer stem (97–141 mm vs. 35–50 mm), broader leaf (19–20 mm vs. 5–8 mm), concave and apically incurved dorsal sepal (vs. slightly concave and apically straight), long acuminate and incurved petals (vs. acute and straight), and long acuminate and apically incurved lip with triangular-uncinate lateral lobes (vs. acute, apically straight with oblong lateral lobes). The biogeography of the species in the series seems to indicate narrow endemism with an Andean center of diversity and limited dispersal to Central America. As such, we hypothesize that both concepts represent separate, morphologically distinct, geographically isolated populations. Ecologically, both species are reported to occur as epiphytes around or below 1,000 m elev., and are likely fly-pollinated.

Two species attributable to series Amphygiae were described after Luer’s (1998) monograph on the series: Pleurothallis grobleri (Luer & Hirtz in Luer 2009: 3) Shaw (2014: 76) and P. thoerleae (Luer in Luer & Thoerle 2012: 337) Shaw (2016: 39). We consulted these descriptions in order to confirm that our new species was not one of them. Rodolfo Solano (pers. comm.) suggested the new species may also be compared to Pleurothallis amphigya Luer & Escobar (1981: 128) and P. quadricuadata Schlechter (1920: 112) . Pleurothallis flavomarginata can be distinguished from all four by the petiolate leaves, which is a unique trait in the series, the yellow margins of the sepals and petals, which is shared only by P. allenii , and the incurved lip apex, another trait that appears to be unique in the series.

Figures

FIGURE 1. Pleurothallis flavomarginata. A. Habit, drawn to 5 cm scale. B. Flower. C. Dorsal sepal. D. Synsepal. E. Petal. F. Upper surface of lip. G. Profile of the ovary, column and lip. B–G drawn to 1 mm scale. Drawn from the holotype.

FIGURE 2. Pleurothallis flavomarginata. Detail of the flower, photograph taken from the holotype.