Costus oreophilus Maas & D.Skinner, 2023

Maas, Paul J. M., Maas-van de Kamer, Hiltje, Andre, Thiago, Skinner, David, Valderrama, Eugenio & Specht, Chelsea D., 2023, Eighteen new species of Neotropical Costaceae (Zingiberales), PhytoKeys 222, pp. 75-127 : 75

Costus oreophilus Maas & D.Skinner sp. nov.

Diagnosis.

Costus oreophilus sp. nov. (Fig. 15 ) can be confused with C. laevis Ruiz & Pav., with which it shares the mostly green bracts and adaxially oriented flowers, but it is distinguished by the puberulous sheaths and leaves and a smaller ligule (3-10 mm vs. 5-20 mm long); moreover the corolla lobes are often recurved, a feature rarely seen in Costus .

Type.

Ecuador, Tunguruhua : Río Verde Grande, 1500 m, 30 Mar 1956, Asplund 20068 (holotype S, 2 sheets S06-1367 & S06-13643; isotype GB) .

Description.

Herb 3-4 m tall. Leaves sheaths 15-20 mm diam; ligule truncate, 3-10 mm long; petiole 5-10 mm long; sheaths, ligule and petiole densely to sparsely puberulous; lamina narrowly elliptic, 20-38 × 7-11 cm, adaxially shiny, glabrous, sometimes rather densely puberulous, abaxially green, densely to sparely puberulous to velutinous, base cordate to acute, apex acuminate (acumen 5-10 mm long). Inflorescence cylindric to ovoid, 7-12 × 3-6 cm, wrapped tightly by the upper leaves, terminating a leafy shoot; bracts, bracteole, calyx, ovary, and capsule sparsely puberulous to glabrous. Flowers adaxially oriented to erect; bracts green in the exposed part, red in the covered part, sometimes completely red, coriaceous, broadly ovate, 3.5-4.5 × 3-4 cm, apex obtuse, callus inconspicuous; bracteole boat-shaped, 18-31 mm long; calyx red, 6-12 mm long, lobes shallowly triangular, 3-4 mm long; corolla white to yellow, 50-60 mm long, glabrous, lobes recurved, narrowly obovate, 40-55 mm long; labellum white, distal edge horizontally spreading, broadly obovate, 70-75 × 70-75 mm, lateral lobes striped with red, middle lobe reflexed, with yellow honey mark, margin irregularly crenulate; stamen red to pink, 35-40 × 12-13 mm, not exceeding the labellum, apex red, irregularly dentate, anther 10-12 mm long. Capsule ellipsoid, c. 15 mm long.

Distribution.

Ecuador (Pastaza, Tungurahua, Zamora-Chinchipe) (Fig. 22D ).

Habitat and ecology.

In forests, at elevations of 1150-1600 m. Flowering in the rainy season.

Etymology.

The species name " Costus oreophilus " is derived from the Greek words oros (= mountain) and philos (= beloved) as this is a mountain-loving species.

Paratypes.

Ecuador. Pastaza: road to Puyo, km 45-60, 1300-1400 m, 8 Oct 1961, Dodson & Thien 913 (WIS). Tungurahua: valley of Río Pastaza, Hacienda Verde Grande, 1500 m, 26 Jul 1939, Asplund 7833 (GB, S); between Río Mapoto and Río Margaritas, along Canelos trail, 1225 m, 20 Mar 1939, Penland & Summers 179 (BM, F, MO). Zamora-Chinchipe: along road Loja-Zamora, km 45-51, 1400-1600 m, 20 Nov 1961, Dodson & Thien 1441 (WIS). Cultivated material: Ecuador, Zamora Chinchipe, Parque Nacional Podocarpus, 1175 m, 25 Jan 2013, Skinner R 3332; Ecuador, Zamora Chinchipe, Río Numbamia, 1270 m, Skinner R 3333.

Notes.

Most collections of Costus oreophilus sp. nov. were placed by Maas (1972) under Costus laevis Ruiz & Pav. with a note saying: "Three Ecuadorian collections deviated by being densely puberulous to velutinous on the lower side [abaxial surface] of the leaves. The flower material being incomplete, I could not determine their taxonomic status, i.e., whether it is a variety of C. laevis or a distinct species". Now, 50 years later, we recognize these specimens merit specific rank. Costus oreophilus differs from C. convexus sp. nov. Maas & Skinner by various features such as the hairy instead of glabrous sheaths and leaves, a smaller calyx (6-12 vs. 15-25 mm long), a smaller ligule (3-10 vs. 20-45 mm long), and recurved corolla lobes, a feature quite rare in Costus .

The authors are indebted to orchid specialist Marco Jiménez Villata of Zamora, Ecuador, who has explored the forests of Zamora-Chinchipe for over 30 years. He showed Dave Skinner several localities in the province, where he was able to make photographs of this species. Skinner later found the living plants of this new species in Tungurahua, which were consistent with the plants in Zamora-Chinchipe but usually with less dense hairs on the undersides of the leaves. Moreover, in living material, the corolla lobes were found to be sharply recurved, which is very unusual in the genus Costus .

Figures

Figure 15. Costus oreophilus Maas & D. Skinner A plant in habitat B inflorescence showing clasping upper leaves and recurved corolla lobes on a fresh flower C flowering shoot showing narrowly elliptic leaf lamina D upper part of inflorescence showing recurved corolla lobes and adaxially oriented to erect labellum. Photos A-D by Dave Skinner taken near La Molienda along the Rio Estancia, Tungurahua, Ecuador.

Figure 22. Distribution maps for new species of Costaceae. Costus gibbosus - Costus whiskeycola m A Costus gibbosus D. Skinner & Maas B Costus mollissimus Maas & H. Maas C Costus obscurus D. Skinner & Maas D Costus oreophilus Maas & D. Skinner E Costus pitalito C. D. Specht & H. Maas F Costus prancei Maas & H. Maas G Costus pseudospiralis Maas & H. Maas H Costus rubineus D. Skinner & Maas I Costus whiskeycola Maas & H. Maas.