Promenaea microptera Reichenbach 1881
Creators: name: Barberena, Felipe Fajardo V. A.
name: Gastin, Jorge Rodrigues
name: Smidt, Eric De Camargo
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Liliopsida
Asparagales
Orchidaceae
Promenaea
Promenaea microptera

description: Promenaea microptera Reichenbach (1881: 134). Figs. 1; 2 A–B.
Type:—S. loc., ex hort., fl. cult. at “James Veitch & Sons”, Chelsea, London, July 1881, A. d’Haene sub H.J. Veitch s.n. (lectotype designated by Meneguzzo 2020: W-R 40606 [W0132796] pencil icon on left, digital image!). Remaining original material:—S. loc., ex hort., fl. cult. at London, July 1881, B.S. Williams s.n. (remaining syntype W-R not found).
= Zygopetalum micropterum Reichenbach (1881: 134), nom. nud.
= Zygopetalum micropterum (Rchb.f.) Bentham & Hooker ex Bois (1893: 133).
Rupicolous herb, 18–25 cm. Rhizome up to 2.0 cm long. Pseudobulbs 2.0–2.5 × 0.3–0.5 cm, ovate to fusiform. Leaves 19–25 × 0.9–1.3 cm, linear-lanceolate, apex acute. Inflorescence 1–2-flowered, 2–4 cm long, bracts 0.8–1.0 × ca. 0.3 cm; bracteoles ca. 0.8 × 0.3–0.4 cm, shorter than the pedicellate ovary; pedicellate ovary ca. 1 cm; sepals and petals ochre-green, spotless, ovate; dorsal sepal 1.8–2 × 0.4–0.5 cm, apex acute, lateral sepals 2–2.1 × 0.6–0.7 cm, apex acute; petals ca. 1.7 × 0.6 cm, apex acuminate; lip ca. 1.4 × 0.6 cm, white, outline elliptic, lateral lobes ca. 0.5 × 0.6 cm, with vinaceous stripes and spots, ovate, erect, apex obtuse, median lobe ca. 0.9 × 0.6 cm, with vinaceous stripes at the base, elliptic, apex acuminate; disk with apex emarginate to 2-toothed, attached to the base on both sides of the two lateral lobes, bearing a transverse crest; callus ca. 0.3 × 0.2 cm, subcylindrical, erect, inserted on the center of the crest, not extending over lateral lobes, apex bilobed; column ca. 1.2 cm long, ochre-green with margins and ventral portion vinaceous, subcylindrical, column foot ca. 0.4 cm long; anther cap ca. 0.4 × 0.3 cm, broadly oblong. Capsule not seen.
Additional examined material:— BRAZIL. Rio de Janeiro: Nova Friburgo, 28 December 2018, J. R. Gastin s.n. (UPCB 93053!). S. loc., ex hort., fl. cult. at Glasnevin Botanic Garden, June 1890, F. W. Moore s.n. (K 879642, digital image!). S. loc., ex hort., fl. cult. at Upper Holloway, London, May 1896, B. S. Williams & Son (H. Williams) s.n. (K 879641, digital image!). S. loc., ex hort., fl. cult. at Glasnevin Botanic Garden, June 1900, s.coll. s.n. (F. W. Moore?) (K 879640, digital image!). S. loc., ex hort., fl. cult. at Kew Gardens, June 1915, s.coll. s.n. (K 879639, digital image!). S. loc., ex hort., s.d., s.coll. s.n. (W-R 31572 [W0132797], digital image!).
Reichenbach (1881) characterized P. microptera by its light ochre-colored flowers, obtuse lateral lobes and lanceolate median lobe of the lip, with some narrow purple zones on the disk, similar maculae on the callus and the base of the lip, and a column with vinaceous margins at the basal portion. He highlighted that the shape of the flower was remarkably similar to that of P. xanthina, but with smaller lateral lobes, the keels at the base of the lip distinctly emarginate in front and with a small, peculiar callus on the disk. In the protologue of P. microptera, two specimens used by Reichenbach (1881) to describe the species are cited. The first was cultivated by Benjamin S. Williams (1822–1890, English horticulturist and orchidologist), but not found, since the location of his herbarium is unknown (Stafleu & Cowan 1988: 315). The second (W-R 40606), cultivated by Adolphe d’Haene in Ghent, Belgium and sent to Harry J. Veitch (1840–1924, English horticulturist), consists of two illustrations made in pencil, which are partially congruent with the original description, as differ a little as to the distribution of the maculae of the lip. Details of the floral morphology of the species can also be seen in the illustrations by Smith & Fitch (1915) (Figure 1).
Bois (1893) and Cogniaux (1906) described the sepals and petals of P. microptera as creamy white or ochre-yellow and the lip as white, although the latter author has stated that he did not observe the specimens mentioned. Schlechter (1921) relied solely on the illustrations in the W-R herbarium (including most likely the lectotype designated by Meneguzzo 2020) to draw his taxonomic conclusions about P. microptera, highlighting the absence of dry material associated with the species. Hoehne (1953) drew on Cogniaux (1906) and Schlechter (1921) to describe P. microptera and considered that it has unique characters (yellowish white flowers, short and triangular lateral lobes and narrow and acute median lobe of the lip), which would certainly allow the easy recognition of the species in the field, should it be found again. Hoehne (1953) also pointed out with some surprise that Reichenbach had not conserved the specimens on which he based his original illustrations and that the species had not been collected since.
Pabst and Dungs (1977) divided the genus into three informal groups, inserting P. microptera in the Promenaea xanthina alliance, characterized by the callus on the disk of the lip that does not reach the lateral lobes and the yellow flowers. The color of the flowers and the immaculate sepals and petals led Barberena (2014) to suggest the synonymization of P. microptera under P. xanthina. More recently, Meneguzzo (2020) synonymized P. microptera under Promenaea stapelioides subsp. xanthina (Lindley) Meneguzzo (2020: 165), but without detailing the reasons for this decision.
However, the analysis of materials deposited in K, UPCB and W-R herbaria, mainly the specimen Gastin s.n. (UPCB 93053), together with the photographs of the specimen taken in the field (Figure 2), are conclusive and allowed us to affirm P. microptera as an autonomous species. Promenaea microptera is mainly characterized by its ochre-green and immaculate sepals and petals; white lip, with reddish-purple areas on the disk of the lip, on the callus, on the lateral lobes and more or less on the basal half of the median lobe, a bilobed callus at the apex, and column with vinaceous maculae mostly at the basal portion and margins. These morphological features are congruent with the protologue of the species. The characterization of P. microptera sepals and petals as creamy white, yellowish white or similar in color, was based on the colored illustration in the W-R herbarium, as indicated by Schlechter (1921). However, this floral coloration has not yet been observed in any living individual or mentioned on the label of any exsiccatae, which may be a morphological variation of the species or a misinterpretation.
Therefore, Promenaea microptera is distinguished from P. xanthina, the closest species morphologically, mainly in the ochre-green sepals and petals (vs. bright yellow sepals and petals, rarely white), disk of the lip with a 2-toothed (vs. 3(–5)- toothed) and bilobed callus at the apex (vs. entire callus). Promenaea microptera can also be confused with P. guttata by having an elliptical median lobe, but they are also primarily distinguished by the color of the sepals and petals (ochre-green vs. pale-yellow) and callus of the lip (bilobed vs. entire).
The scarcity of materials and information on P. microptera is notorious and highlighted by several authors in the last decades. The original protologue offers no information on the geographical origin of the original material used by Reichenbach. Bois (1893) was possibly the first to assume data on geographic distribution of the species when indicating Brazil. This position was maintained by other authors (e.g., Cogniaux 1906; Schlechter 1921; Hoehne 1953), considering that P. xanthina and the other species of Promenaea were known only from Brazil, although the true origin of the species has never been proven. Our findings, however, allowed us to put an end to this situation. Promenaea microptera is a microendemic species to the Brazilian Atlantic Forest, occurring around Nova Friburgo, in the state of Rio de Janeiro. The species was found growing rupicolously in moss-covered granitic rocks, near a stream in dense montane forests, at 800–1,000 m altitude. Given the absence of collections for over 100 years and the punctual distribution, P. microptera can be considered a rare species and conservation actions need to be taken in order to maintain the local population and ensure the species’ existence.
E. C. S. was supported by Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) for a “Bolsa de Produtividade em Pesquisa CNPq - Nível 1D” [grant number 314642/2020-0].
description: Published as part of Barberena, Felipe Fajardo V. A., Gastin, Jorge Rodrigues & Smidt, Eric De Camargo, 2022, Taxonomical remarks on Promenaea microptera (Orchidaceae: Epidendroideae): the rediscovery of a poorly known micro-endemic orchid from the Brazilian Atlantic Forest, pp. 229-233 in Phytotaxa 545 (2) on pages 229-232, DOI: 10.11646/phytotaxa.545.2.12, http://zenodo.org/record/6534614