Sabicea urniformis Zemagho, O. Lachenaud & Sonké,
Zemagho, Lise A., Lachenaud, Olivier, Dessein, Steven, Liede-Schumann, Sigrid & Sonke, Bonaventure, 2014, Two new Sabicea (Rubiaceae) species from West Central Africa: Sabicea bullata and Sabicea urniformis, Phytotaxa 173 (4), pp. 285-292: 286-288
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|Sabicea urniformis Zemagho, O. Lachenaud & Sonké|
Creeping and twining liana; stems up to 5 m long; 2–3 mm thick; twigs hirsute with long (ca. 2 mm) patent hairs intermingled with short appressed woolly hairs. Stipules persistent, entire, reflexed (rarely erect), ovate to suborbicular, acute at the top, 5–10 × 3–6 mm, glabrous on adaxial surface, hirsute on the abaxial surface. Leaves opposite, equal; petioles 0.2–3 cm long, with same indumentum as the twigs; blades elliptic, 3–15.8 × 1.6–7.4 cm, upper side darkish green, densely to sparsely villose with straight hairs, lower side grey white to pale buff, with a dense felt of short woolly hairs (sometimes sparser) intermingled with sparser, long stiff hairs; base obtuse, rarely acute; apex acuminate; secondary nerves 9–17 on each side of the mid-vein, distinctly bullate above in life. Inflorescences capitate and involucrate, 9–14 flowered, sessile or shortly (to 0.4 cm) pedunculate; involucre narrowly urn-shaped at anthesis, patent and star-like in fruit, consisting of at least two pairs of bracts; bracts green, ovate to narrowly ovate, apex acute, densely villose on both sides with straight hairs, sometimes intermingled with woolly hairs on outer side; the outer pair (11–)14–30 × 6–13 mm, shortly connate at base at anthesis, splitting in fruit; the inner pairs slightly smaller and free. Flowers 5-merous, sessile. Calyx green, tube ca. 1 mm long; lobes narrowly triangular to linear, 3–5 mm long, apex acute, densely covered with long silky hairs. Corolla white, tube 15–20 mm long, lobes 2–3 mm long, covered with long appressed silky hairs outside, shortly pubescent in upper half inside. Stamens half-exserted (short-styled flowers) or included (long-styled flowers); anthers 1.25–1.5 mm long, base glabrous, apex pubescent. Ovary 5-locular; style 5- lobed, included, ca. 12 mm long (short-styled flowers) or exserted, 17–19 mm long (long-styled flowers). Fruits sessile, ovoid to obovoid, 17 × 15 mm in vivo, hirsute, white, topped with persistent calyx. Seeds, numerous, not mature.
Distribution and Ecology:— Sabicea urniformis is known from southwest Gabon, where it is locally common, and adjacent Congo-Brazzaville ( Fig. 2). It grows in forest edges and in secondary forest.
Phenology:—Probably flowering and fruiting the whole year round.
Notes:—This plant was first recognized as new species by N. Hallé, as indicated on the specimen Dowsett- Lemaire 1434. Sabicea urniformis is remarkable in its involucre, of which the two outer bracts are shortly connate into a narrow urn-shaped structure at anthesis (hence the specific name) before splitting and becoming patent in fruit. This is unusual in Sabicea , where most species have free bracts. In this character S. urniformis superficially resembles S. urceolata Hepper (1958: 293) , but the latter has bracts almost entirely connate, red fruits, and the leaves are green on both sides.
In general habit, S. urniformis also resembles S. becquetii (N.Hallé) Razafim., Bremer, Liede & Khan ( Hallé 1964: 400; Khan et al. 2008: 20), but the two species have widely separate ranges and are presumably not related; S. becquetii differs in its free bracts and red 2-locular fruits. Sabicea urniformis is probably more closely related to S. capitellata Benth. ( Hooker 1849: 398) s.l., also with discolorous leaves and white 5-locular fruits, but differing in having much smaller flowers and bracts, the latter free. Differences between all these species are summarized in Table 1.
Leaves discolorous discolorous green on both sides discolorous
Involucre shape hemispherical hemispherical narrowly urceolate narrowly urceolate in flower, patent and star-like in fruit
Bracts free free almost entirely connate, splitting shortly connate at base, splitting in fruit down one side in fruit
Corolla tube 9 –11 mm 7 –8 mm ca. 25 mm 15 –20 mm
Ovary 2-locular 5-locular 5-locular 5-locular
Fruit colour red white red white
Distribution Burundi Cameroon to D.R. Nigeria to Gabon Gabon and Republic of Congo
Conservation status: — Under Criterion B, Sabicea urniformis qualifies for vulnerable based on the Extent of Occurrence (14981.96 km 2) and endangered based on Area of Occupancy (44 km 2, grid cell size 2 km). However, there is no clear threat for the species at present. Forests are relatively well managed in the area where the species is found, and in addition S. urniformis , like most of its congeners, is a forest edge species, relatively adaptable to habitat degradation. Therefore the species is for now considered as Least Concern.
Paratypes:— REPUBLIC OF CONGO (BRAZZAVILLE). Kouilou : Mayombe à Béna, 20 December 1990, Dowsett-Lemaire 1434 (BR); Béna, Lisowski B-7164 (BR) .
GABON. Rabi Kounga site 2 S, 1 June 2002, Bouroubou et al. 681 (MO); between Rabi-Kounga and Yeno, 16 May 1992, Breteler et al. 11478 (LBV, WAG); Rabi-Kounga , 9 July 1998, Breteler et al. 14362 (BR, LBV, WAG); concession de Rabi-Shell, entre Rabi et Toucan, 23 January 2010, Dauby et al. 2108 (BRLU); Nyanga, Gamba, 12.4 km from Gamba airport in SE direction; 30 November 1994, J.J.F.E. de Wilde & de Wilde-Bakhuizen 11259 (WAG); concession Maurel & Prom près du Lac Ezanga, 22 November 2013, Lachenaud et al. 1532 (BR, BRLU, LBV, MO, P, WAG); road between Rabi and Eshira, 22 January 1988, J.M. & B. Reitsma 3571 (LBV, WAG); Rabi-Kounga , southside, 9 October 1991, Schoenmaker 2 (LBV, WAG); Nyanga, Mayumba, ca. 20 km along the road to Ndindi, 31 March 2001, Tabak & van Os 235 (WAG); Ogooué-Maritime: Rabi , 4,5 km on road to Divangui, roadside, 4 March 1994, Wieringa & Haegens 2390 (LBV, WAG); Ngounié, 52 km road Mandji to Yeno , 19 January 2005, Wieringa et al. 5584 (WAG) .
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