Keetia namoyae O. Lachenaud & Q. Luke

Olivier Lachenaud, Quentin Luke & Benny Bytebier, 2017, Keetia namoyae (Rubiaceae, Vanguerieae), a new species from eastern Democratic Republic of Congo, Candollea 72 (1), pp. 23-26 : 24-26

Keetia namoyae O. Lachenaud & Q. Luke , spec. nova ( Fig. 1 ).

Typus: DEMOCRATIC REPUBLIC OF CONGO. Prov. Maniema: Namoya, Mwendamboko Hill , 4°00’05”S 27°32’94”E, 12.IV.2008, fl. & fr., Bytebier & Luke 2796 (holo-: BR [ BR000000524731 ]!; iso-: EA!).

Foliis glabrescentibus et coriaceis venulis tertiariis inconspicuis K. tenuiflorae (Hiern) Bridson et K. mannii (Hiern) Bridson similis, sed ab ambabus speciebus conspicue differt ramis floriferis alternis (nec oppositis) cum indumento sparso et valde appresso, inflorescentiis paucifloris, floribus majoribus corollae tubo c. 4 mm longo (nec c. 2 mm) fructibusque majoribus c. 20 x 20 mm apice paullo emarginatis.

Scandent shrub to 2 m high, with branches alternate and directed backwards, subtended by normal (not modified) leaves. Twigs rather sparsely covered with very stiffly appressed hairs, which persist for a long time on the woody, medium brown bark. Stipules c. 2 mm long, shortly triangular with apex laterally compressed, with same indumentum as twigs, very soon caducous. Leaves with petiole 4-7 mm long, stiffly appressedpubescent; blade elliptic, acute at base, acuminate at tip, 4-9 x 2.2-4 cm, very coriaceous, glabrous above, sparsely appressedpubescent on midrib beneath, drying dull brownish-green with underside paler; lateral nerves 4-6, not strongly prominent; tertiary veins invisible or almost so; small tuft-domatia present in axils of lateral nerves along midrib. Inflorescences cymose, 10-15-flowered, c. 1.5 cm long including c. 0.5 cm long peduncle, shortly branched, sparsely pubescent. Bracts small, c. 1.5 mm, triangular and acute at apex, ciliate. Flowers (4-)5-merous; pedicels 2-5 mm, densely appressed-pubescent. Calyx split almost to the base into narrowly triangular teeth c. 0.75 mm long, shortly ciliate on the margin. Corolla cream; tube cylindrical, 4 x 1.5 mm, glabrous outside, hairy inside with a ring of long (c. 1 mm) abruptly deflexed hairs near the lower 1/4th, and short sparse hairs above reaching just under the throat; lobes 2 mm long, reflexed, glabrous. Flower buds cylindrical with a rounded head. Anthers almost completely exserted, erect, c. 1 x 0.5 mm. Disk shortly pubescent. Style glabrous, exceeding throat by 3 mm and ending in a hood-like stigma c. 0.7 mm long. Fruit slightly obovate, 20 x 20 mm, rounded at base, very shallowly emarginate at apex, glabrous; pedicel reaching c. 8 mm.

Etymology. – The species is named after its only known locality.

Distribution and ecology. – Keetia namoyae is only known from the type locality in Maniema Province, eastern D.R. Congo ( Fig. 2 ). It was found only once in disturbed, open secondary rain forest, at an altitude of 977 m. The following species were recorded in the vicinity: Adenia tricostata De Wild. , Aidia micrantha (K. Schum.) F. White , Aptandra zenkeri Engl. , Argomuellera pierlotiana J. Léonard , Boehmeria macrophylla Hornem. , Celosia globosa var. porphyrostachya C.C.Towns. , Crassocephalum rubens (Jacq.) S. Moore , Cyperus distans L.f., Dichapetalum sp., Dichapetalum parvifolium Engl. , Dioscorea sp., Monanthotaxis sp., Justicia tenella (Nees) T. Anderson , Lindackeria schweinfurthii Gilg , Macaranga sp. nov. (Bytebier & Luke 2805), Puelia ciliata Franch. , Rhabdophyllum welwitschii Tiegh. , Rutidea insculpta Bridson , Solanum welwitschii C.H. Wright , Spermacoce exilis (L.O. Williams) W.C. Burger & C.M. Taylor , Thecacoris lucida (Pax) Hutch. and Tricalysia pallens Hiern.

Fig. 1. – Keetia namoyae O. Lachenaud & Q. Luke. A. Flowering twig; B. Fruiting twig; C. Node with stipules; D. Detail of a domatia; E. Flower bud; F. Open flower; G. Longitudinal section of flower; H. fruit.

[Bytebier & Luke 2796, BR] [Drawing: Antonio Fernandez]

Conservation status. – This plant is known from a single location sensu IUCN (2012); the extent of occurrence is therefore not calculable, and the area of occupancy is estimated as 4 km ². It was collected on a hill that was due to be mined for gold; a decline in the area of occupancy, habitat extent and quality, number of locations and number of individuals is therefore expected. No other individuals are known, although the area has several other hills and is at the edge of extensive primary forest. The species is therefore assessed to be “Critically Endangered” [CR B2ab(ii,iii,iv,v)+D1] of the IUCN (1991).

Notes. – Keetia namoyae is a rather distinctive species due to its very large fruits, small coriaceous leaves with inconspicuous tertiary venation, and twigs with sparse and very stiffly appressed hairs. Due to the appressed-pubescent twigs and lack of conspicuous tertiary veins, K. namoyae most closely resembles K. tenuiflora (Hiern) Bridson and some forms of K. mannii (Hiern) Bridson (the latter usually has glabrous twigs, but occasional variants with pubescent twigs occur). However, these two species differ from K. namoyae in many characters, including: flowering twigs opposite, with indumentum not so stiffly appressed; flowers more numerous (at least 25 per inflorescence, often more) and distinctly smaller, with corolla tube c. 2 mm long only; fruits smaller, <12 mm long, frequently 1-seeded, or if 2-seeded then strongly bilobed. Keetia tenuiflora further differs from K. namoyae in having a pale buff-grey bark.

Although BRIDSON (1991: 921) described the fruits of K. tenuiflora as “ 1.2-1.5 cm long, 2 cm wide”, this appears to be erroneous; the largest fruits we have seen in this species are 12 mm long and 17 mm wide.

Figures

Fig. 1. – Keetia namoyae O. Lachenaud & Q. Luke. A. Flowering twig; B. Fruiting twig; C. Node with stipules; D. Detail of a domatia; E. Flower bud; F. Open flower; G. Longitudinal section of flower; H. fruit. [Bytebier & Luke 2796, BR] [Drawing: Antonio Fernandez]

Fig. 2. – Distribution map of Keetia namoyae O. Lachenaud & Q. Luke (white square).