Costus loangensis H.Maas & Maas

Kamer 1, H. Maas-van de, Maas 1, P. J. M., Wieringa 1, J. J. & Specht, C. D., 2016, Monograph of African Costaceae, Blumea 61 (3), pp. 280-318 : 304

15. Costus loangensis H.Maas & Maas — Map 7

Costus loangensis H.Maas & Maas (2012) 12, f. 1. — Type: Maas et al. 10184 (holo WAG 2 sheets [ WAG0380168 , WAG0380169 ]; iso K, LBV, MO, P, UC), Gabon, Ogooué-Maritime, Parc Nacional de Loango , between Lodge and Staff building, wet forest on white sand, along forest trail, at about sea level, 9 Nov. 2011 .

Etymology. Costus loangensis is named after the place where it has been collected near Loango Lodge, in Parc Nacional de Loango in Gabon. Costus loangensis was discovered upon seeing a photograph of an unknown Costus in Vande Weghe’s book on plants and animals of Gabon’s National Parks (2007:278, f. 623).He describes and publishes a photo of a specimen of Costus ‘which seems to be quite typical for these coastal forests’. We, however, found only a single population.

Terrestrial herb, 0.5–0.6 m tall, shoots dark brownish red. Leaves few (6–7) concentrated at the apex of the shoot; sheaths dark red, 0.6–0.8 cm diam; ligule membranous, 2-lobed, 15–18 mm long; petiole 5–6 mm long; sheaths sparsely to rather densely covered with erect to half-appressed hairs c. 2 mm long, ligule and petiole densely to rather densely so; lamina dark olive-green, zone along midrib sometimes reddish, nar- rowly elliptic to elliptic, 14–16 by 5–6 cm, densely to rather densely covered with erect to half-appressed hairs 1.5–2 mm long on both sides, base attenuate, apex acute. Inflorescence 3–5-flowered, ovoid, c. 2 by 1–1.5 cm, terminating the leafy shoot; outer side of bracts, bracteoles and calyx densely covered with appressed to half-appressed hairs <1 mm long, ovary sparsely so. Flowers 1 per bract; bracts reduced, brown to reddish brown, chartaceous, narrowly ovate-triangular to ovate-triangular, 1.7–2 by 0.5–1 cm, callus 2.5–3 mm long; appendages absent; bracteole boat-shaped, 15–18 mm long, callus 1.5–2 mm long; calyx 11–12 mm long, lobes deltate, c. 2 mm long, callus c. 1 mm long; corolla yellow, 50–55 mm long, rather densely covered with half-appressed hairs <1 mm long, particularly near the apex, tube 20–25 mm long, lobes narrowly elliptic, 30–35 mm long, together forming a hood over the throat opposite the labellum, apex with a callus-like thickening; labellum completely yellow, horizontally flattened with funnel-shaped base, broadly obovate when spread out, 30–40 by 40–50 mm, margin fimbriate (fimbriae 2–3 mm long); stamen yellow, 25–30 by 7–10 mm, anther 5–7 mm long. Capsule and seeds not seen.

Distribution — Central Africa ( Gabon). Only known from the type collection.

Habitat & Ecology — In wet rainforest, on white sand, at elevations of about sea level. Flowering and fruiting: November.

IUCN Conservation Status — Costus loangensis has only been collected once (AOO = 4 km 2), just outside a National Park. Although this locality is within the buffer zone around the park, this locality is used for the construction of tourist accommodations. To our knowledge there exist only few mature individuals of this species. We therefore access this species as Critically Endangered (CR) B2ab(iii,v); D .

Notes — Costus loangensis , known only from the type collection, is a species of small (c. 0.5 m tall) plants with few (6 or 7) leaves, completely yellow flowers and unappendaged bracts. Shoots and leaves are covered with a dense indument of erect to half-appressed hairs. Costus loangensis differs from the very similar C. ligularis , another species of small size with a dense indument, by the colour of its flowers; those of C. ligularis are pale pink rather than bright yellow in C. loangensis . Moreover, the bracts of C. ligularis are generally appendaged.

Figures

Map 7 Distribution of Costus gabonensis Koechlin (●) and C. loangensis H.Maas & Maas (■