Lepanthes dignumii B.T.Larsen & Salas Guerr., 2018

Larsen, Bruno, Guerrero, Marcos Salas & Dignum, Johannes H. M., 2018, Two new peruvian species of Lepanthes (Orchidaceae) with a unique column morphology, Phytotaxa 373 (4), pp. 291-296 : 291-294

Lepanthes dignumii B.T.Larsen & Salas Guerr. , sp. nov. ( Figs. 1 , 3A )

Type:— PERU. Amazonas ; Prov. Chachapoyas, Leimebamba Dist., El Negro-Cordillera de Yasgolga , 3228 m, 20 October 2016, Salas, Dignum et al. 117 (holotype: CPUM) .

This species is distinguished from all other known Lepanthes species by the combination of flowers with deeply concave dorsal sepals and spiculate margins and a conspicuous, glabrous, obovate, convex, acutely angled helm-like apex on the dorsal part of the column.

Epiphytic, sympodial, caespitose herbs up to 3 cm tall. Roots slender, to 0.5 mm in diameter. Ramicauls erect, 1.0– 1.5 cm long, enclosed by 3–4, microscopically scabrous lepanthiform sheaths with acuminate, minutely ciliate ostia. Leaves erect, elliptical, obtuse, 0.9–1.5 X 4.0– 4.7 mm, base cuneate into a petiole 1 mm long. Inflorescence a loose, flexuous, successively many-flowered raceme up to 6 cm long, including the 1.5 cm long peduncle; floral bracts 1.5 mm long; pedicels 1.5 mm long; ovary 1.2 mm long with dentate ribs. Sepals pale yellow, suffused with purple along the veins, glabrous, carinate along the veins, margins spiculate, the dorsal sepal ovate, deeply concave, 4.6 X 2.7 mm, 3-veined, connate to the lateral sepals for 0.5 mm, the lateral sepals connate 2.5 mm into an ovate, concave synsepal, 5.5 X 3.0 mm, each 2-veined, the apices acute, acuminate. Petals pale rose, suffused with purple along the inner and outer margins, minutely pubescent, transversely bilobed, 0.7 X 4.0 mm, lobes oblong, subsimilar, with rounded ends. Lip pale rose, bilaminate, the blades oblong, glabrous, the external margins revolute, 2.5 X 0.5 mm, the bases obliquely truncate, the apices truncate, long-ciliate, the connectives cuneate, the body connate to the column above the base, the sinus obtuse with a aristate appendix. Column pale purple, 1.0 X 0.3 mm, the dorsum with a glabrous, obovate, convex, acutely angled apex, 1.0 X 0.7 mm, from above the base of the column, with a smooth median keel, the sides projecting 0.3 mm on each side forcing the blades of the lip to bend outwards at the end of the connectives, base rounded, apex truncate with the dorsal anther, stigma apical. Anther cap pyriform, apex emarginate, sitting on the apex of the column. Pollinia 2, narrowly obpyriform, sub attenuate at the base, on an oblong viscidium. Capsule not seen.

Eponymy:— Dedicated to Johannes Dignum, Dutch ecologist focused on community-based conservation of endangered cloud forest ecosystems in Peru and Colombia through the development of sustainable local economies that support the objective of conservation and co-collector of the type specimen.

Distribution and habitat:— Known from one collection in the El Negro Chico area, in the direction of the Chilchos Valley, epiphytic in humid montane forest.

Conservation Status:— Evaluated as data deficient (DD), according to the IUCN (2001) classification.

Phenology:— Recorded to flower in October.

Comments:— Lepanthes dignumii and L. leimebambana B.T.Larsen, Salas Guerr. & Dignum ( Figs. 2 , 3B , 4 ) are unique in column structure, as described in the introduction. Our initial thought was that this large, oval-shaped structure might be only the anther cap covering the clinandrium, but fruitless attempts were made to lift it up to expose the pollinia. In L. dignumii , as in all Lepanthes species, the anther cap and pollinia are located at the apex of the column. Lepanthes dignumii can be distinguished from L. leimebambana by the shorter pedicels (1.5 mm in L. dignumii vs. 4.0 mm in L. leimebambana ) and flowers with deeply concave dorsal sepal (vs. shallowly concave in L. leimebambana ), Finally, L. dignumii can be easily distinguished from all other species of Lepanthes by flowers with carinate, deeply concave dorsal and lateral sepals and spiculate margins, petals with oblong lobes with rounded ends and an oval-shaped apex in the dorsal part of the column.

Figures

FIGURE 1. Lepanthes dignumii B.T.Larsen & Salas Guerr. A. Habit. B. Flower. C. Dissected flower. D. Lip, column and ovary, lateral view. E. Column and lip, dorsal view. F. Lip, dorsal view. G. Column, dorsal view. H. Anther cap and pollinia. Drawn from the holotype by Bruno Larsen.

FIGURE 2. Lepanthes leimebambana B.T.Larsen, Salas Guerr. & Dignum.A. Habit. B. Peduncle with flower bract and pedicel. C. Flower. D. Dissected flower. E. Column, lip and ovary, lateral. F. Column and lip, dorsal view. G. Lip, dorsal view. H. Column, dorsal view. I. Anther cap and pollinia. Drawn from the holotype by Bruno Larsen.

FIGURE 3. A. Lepanthes dignumii. B. Lepanthes leimebambana (photographs by M. Salas Guerrero).

FIGURE 4. Lepanthes leimebambana at the type locality in Leimebamba, Peru (photograph by M. Salas Guerrero).