Vanilla arcuata Pansarin & M. R. Miranda. A. Habit. B. Inflorescence 2016, sp. nov.
Creators: name: Pansarin, Emerson R.
name: Miranda, Marcelo R.
Publisher: name: Zenodo
Year: 2016
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Liliopsida
Asparagales
Orchidaceae
Vanilla
Vanilla arcuata

description: Vanilla arcuata Pansarin & M.R. Miranda, sp. nov. (Fig. 1)
Vanilla arcuata differs from the remaining species of the Vanilla mexicana Miller (1798: without page number) group by its strongly arcuate column and its convex and white labellum that contrasts with the yellow central crest.
Type: — BRAZIL. São Paulo: Mun. Caraguatatuba, Mata de Restinga, 7 March 2015, E.R. Pansarin & M.R. Miranda 1514 (holotype: LBMBP!, Dried Collection).
Hemiepiphyte herbs ca. 7–18 m tall, marshy. Aerial roots 18–35 × 1.8–2.5 mm, whitish, glabrous. Aerial stem 3–4.5 cm diam., green, ramified at the apical portion, with up to seven racemose inflorescences; internodes 3.5–15 cm long. Leaves 12–18 × 4.5–9.5 cm, oval, plain, coriaceous, distichously disposed, green or green-yellowish, with dark green veins forming a network, margin entire, apex acute to acuminate, reflex. Inflorescence ca. 5–6 cm long, lateral, erect, with 2–3 flowers opening in succession; scape ca. 2–3 mm diam., cylindrical, sinuous, green-yellowish; floral bracts 1.8–4 × 0.9–1.6 cm, elliptic to oval, green-yellowish, persistent. Flowers resupinate, predominantly greenish; ovary and pedicel 4.3–6.1.6 × 0.32–0.4 cm, green-yellowish; abscission layer between perianth and ovary present; sepals elliptic to lanceolate, enrolled, pale green, margin undulate, apex acute, lateral sepals ca. 4.5 × 1.7 cm, asymmetrically elliptic; apical sepal ca. 4.7 × 1.5 cm, symmetrically lanceolate; petals 4.4–4.6 × 1.6–1.8 cm, asymmetrically lanceolate, enrolled, pale green, margin undulate, apex acute; labellum 3–lobed, 3.8–4.2 × 2.8–3 cm long, oval, white with a prominent central callus; margins united to the basal portion of the column forming a yellow mentum of 0.7–0.9 mm long; central callus with three longitudinally disposed yellow keels; lateral lobes round enrolled back, margin entire; apical lobe oval, margin undulate. Column ca. 3 cm long, strongly arched, clavate, white, with a yellow keel at the base (mentum region), and with only the basal and the apical portions inside the labellum; stigma ca. 3 × 1 mm, transversally oblong; anther ca. 5 × 3.5 mm, versatile, white, with two projections at the apical portion; rostellar flap semicircular, prominent; pollen free, yellow. Fruits linear green, opening through two longitudinal valves. Seeds crustose, spherical, black.
Distribution and ecology: —The species has been reported for the Atlantic Coast of the state of São Paulo, municipality of Caraguatatuba, Brazil. In this locality, Vanilla arcuata occur in coastal plain (“restinga” vegetation), in marshy forests, and growing as hemiepiphyte on sandy soil and close to the beach. The mean elevation is ca. 3 m. a.s.l..
Phenology: — The species has been collected with flowers from February to March.
Etymology:— The specific epithet (arcuata) makes reference to the strongly arched column, which is outside of the convex labellum.
Conservation status: —Based on the evidence that natural habitat has been devastated in the interior costal plane of the state of São Paulo, Vanilla arcuata can be considered as a vulnerable (VU) species according to IUCN Red List Category (2001).
Additional specimens examined (paratypes):— BRAZIL, São Paulo: Mun. Caraguatatuba, Mata de Restinga, 7 March 2015, Pansarin & Miranda 1515; 7 March 2015, Pansarin & Miranda 1516 (LBMBP, Dried Collection).
Taxonomic relationships: — Vanilla arcuata is easily recognized by its strongly arcuate column and its convex and white labellum that contrasts with the central and yellow crest. These characters differ significantly from the remaining species of the Vanilla mexicana group, which are characterized by the occurrence of a yellowish-green central crest made by numerous keels or an elevated callus. In the remaining species of the Vanilla mexicana group the column is inside a tubular labellum and the basal keel on abaxial surface of the column has been considered as absent.
Discussion:— The vegetative and floral morphology of Vanilla arcuata is related to the V. mexicana group. The Vanilla mexicana group includes eight species characterized by the presence of usually enrolled sepals, undulate petals, a very wide labellum with three to five lobes and numerous keels or an elevated callus (Soto Arenas & Cribb 2010). Furthermore, the absence of a keel on the abaxial surface of the column has been considered as a characteristic common to members of the Vanilla mexicana group (Soto Arenas & Cribb 2010). The use of columnar keel to define the groups within Vanilla needs a revaluation. Vanilla paludosa Pansarin, et al. (2012b: 157), has been considered as a member of the V. parvifolia Barbosa Rodrigues (1881: 271) group based on the presence of a keel on abaxial surface of the column, (Pansarin et al. 2012b). However, the inclusion of V. paludosa in a molecular phylogenetic analysis reveal this species is more closely related to species of the V. mexicana group (E.R. Pansarin, unpubl. data). According to Soto Arenas & Cribb (2010), the Vanilla parvifolia group, which includes the reticulate-veined vanillas, is characterized by the presence of non-undulate petals, not coiled sepals, 3-lobed lip with a rounded apical lobe and also a column with a basal triangular keel on the abaxial surface. According to our our investigations, however, some members included in the V. parvifolia group (Soto Arenas & Cribb 2010), possess undulated petals, revolute sepals and labellum with acute to triangular apical lobe (Pansarin et al. 2012b).
The marshy and hemiepiphyte habit as recorded here for V. arcuata is an uncommon condition within Vanilla. The majority of the hemiepiphyte species show a terrestrial habit, except V. paludosa, which occur in marshy forests adjacent to Cerrado areas in the state of São Paulo, Southeastern Brazil (Pansarin et al. 2012b).
According to Pansarin (2010a) and Pansarin et al. (2012a), the Brazilian biomes are the center of diversity for the main genera of vanilloid orchids. Consequently, the knowledge about the taxonomy and phylogenetic analysis including members of Brazilian Vanilloideae are fundamental to understand the evolution of this orchid subfamily (Pansarin et al. 2012a).
description: Published as part of Pansarin, Emerson R. & Miranda, Marcelo R., 2016, A new species of Vanilla (Orchidaceae: Vanilloideae) from Brazil, pp. 84-88 in Phytotaxa 267 (1) on pages 85-87, DOI: 10.11646/phytotaxa.267.1.9, http://zenodo.org/record/13657442