Costus talbotii Ridl.

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 : 311

23. Costus talbotii Ridl. — Plate 4e ; Map 9

Costus talbotii Ridl. (1913) 111. — Type: Talbot 1521 (lecto BM 2 sheets, designated by Turner (2000); isolecto K), Nigeria, Cross River State, Oban , anno 1912 .

Epiphytic or terrestrial herb c. 0.5 m tall. Leaves several; sheaths 0.2–0.5 cm diam; ligule brown, membranous, truncate, 40–55 mm long; petiole 3–10 mm long; sheaths, ligule and petiole glabrous; lamina narrowly elliptic, 10–18 by 3–5 cm, glabrous on both sides, coriaceous and somewhat fleshy, base obtuse to acute, apex acuminate (acumen 10–20 mm long). Inflorescence few-flowered, broadly ovoid, 2–3 by 1.5–2.5 cm, terminating a separate leafless shoot <1 cm long, lateral in the axil of a leaf, or rarely terminal, sheaths dark brown, broadly to transversely elliptic, 6–14 by 9–15 mm; bracts sparsely to rather densely covered with appressed hairs <1 mm long, bracteoles, ovary and capsule rather densely covered with erect hairs <1 mm long, calyx glabrous or sparsely covered with appressed to erect hairs <1 mm long. Flowers 2 per bract; bracts reddish brown to dark brown, coriaceous, broadly ovate-triangular, 1.2–2 by 1.3–2 cm, callus absent or sometimes present and c. 0.5 mm long; appendages absent; bracteole boat-shaped, 15–20 mm long, callus green, 1–2 mm long; calyx green, dark reddish dotted, 11–15 mm long, lobes broadly to shallowly triangular, 2–4 mm, callus 1–2 mm long; corolla tube white, lobes hyaline, dark pink, 35–40 mm long, glabrous, tube c. 10 mm long, lobes narrowly elliptic, 25–30 mm long; labellum white on the outer side, inner side white to dark pink with pink dots in the throat and yellow nectar guide, horizontally flattened, broadly obovate when spread out, 30–40 by 30–40 mm, margin indistinctly ir- regularly 5-lobed, crenate; stamen white with pink dots, c. 25 by 8–9 mm, apex pink, 3-lobed, lobes linear, middle lobe longer than the lateral ones, anther 5–6 mm long. Capsule ovoid to broadly ovoid, 9–15 by 7–9 mm. Seeds 2–2.5 by 1 mm.

Distribution — West Africa (Nigeria, near the border with Cameroon). At unknown elevations.

Habitat & Ecology — Unknown. Flowering and fruiting: unknown.

IUCN Conservation Status — Costus talbotii was collected as a herbarium specimen twice in the wild, both collections were made in the same area over 100 years ago without precise locality information (one location, AOO of 4 or 8 km 2). However, since it apparently was collected more recently (1978) for cultivation in a botanical garden, we do not consider this species as Extinct in the Wild. The area where it was collected (SE Nigeria) is poorly explored over the past 40 years, so it is not a surprise there are no recent collections: on the other hand it was not collected in the decades before that (or only once as living plant) when there was more botanical activity in the region. In this area there are extensive protected areas present, but satellite images show there is also logging, cultivation and mining going on in the area, including in some of the protected areas. So it seems at least part of this area is under serious threat for habitat destruction. We therefore assess the species as Critically Endangered (CR) B2a(iii,v).

Notes — Costus talbotii is distinct from the two other epiphytic African species of Costus by its much broader (to c. 2 cm wide) coriaceous bracts vs the chartaceous bracts (to 1.1 cm wide) in C. lateriflorus and C. lilaceus . Moreover, the flower colour of the three species is clearly different. Costus talbotii is a very incompletely known species: it is only known from the type collection and from cultivation. This plant has been cultivated at the Cambridge Botanical Garden in England under the accession number 19780014. It had been collected in Oban, Cross River State, Nigeria (the type local- ity) in 1978, where it was gathered by P.W. Richards, then Professor at the Cambridge University. This material died in the Cambridge Botanical Garden in 1996. Luckily living material had been sent to the Delft Botanical Garden in The Netherlands where it is still cultivated under the number Delft 46-490. From Delft some living plants were sent to Burgers’ Zoo in Arnhem ( The Netherlands), where it is now grown under the number Burgers’ Bush 2008-0109009. The plant flowered in 2009 and was photographed, described and collected by the second author (Maas et al. 9800). Of the two syntypes of C. talbotii, Zenker 3823 ( BM, E, G, K, US, WRSL), anno 1909, from Bipindi, Cameroon does not rep- resent C. talbotii but belongs to C. lateriflorus or to C. lilaceus .

Figures

Plate 4 a. Costus macranthus K.Schum. Habit, flower and details of stamen, stigma and style. – b. Costus nimba H.Maas & Maas. Basal inflorescence. – c. Costus spectabilis (Fenzl) K.Schum.Habit with flowers. – d. Costus lucanusianus J.Braun & K.Schum. Inflorescence with 4 flowers.– e. Costus talbottii Ridl. Flower. – f. Costus louisii H.Maas & Maas. Inflorescence (a: Wright 1905: t 7992; b: Jongkind 11301; c: photographed in Rumonge, SW Burundi, no specimen collected; d: Maas et al. 10000; e: Maas et al. 9800; f: Maas et al. 10339). — Photos: a, b, d–f: P.J.M.Maas; c: E. Fischer.

Map 9 Distribution of Costus lilaceus Maas & H.Maas (●) and C. talbotii Ridl. (▲).