Sabicea becquetii (N. Hallé 1964: 400 ) Razafimandimbison, B. Bremer, Liede & S.A. Khan

Zemagho, Lise A., Liede-Schumann, Sigrid, Lachenaud, Olivier, Dessein, Steven & Sonke, Bonaventure, 2017, Taxonomic revision of Sabicea subgenus Anisophyllae (Ixoroideae, Rubiaceae) from Tropical Africa, with four new species, Phytotaxa 293 (1), pp. 448-450 : 448-450

4. Sabicea becquetii (N. Hallé 1964: 400) Razafimandimbison, B. Bremer, Liede & S.A. Khan (in Khan et al. 2008:

14) ( Fig. 11 )

Pseudosabicea becquetii N. Hallé (1964: 400) .

Type:— BURUNDI. Bururi, chefferie Ararawe , 1600 m, September 1932, A. Becquet 115 (holotype BR [ BR0000008852151 ]!; isotypes BR [ BR0000008851918 ]!, K [K000414631]!, P [P00077584]!) .

Scrambling shrub or woody vine; stems often sarmentose, up to 3 m long, 2–4 mm thick, sometimes much shorter and prostrate, with sparse felt of woolly hairs often intermingled with long patent hairs 1.5–2 mm long. Leaves opposite, slightly unequal to subequal; petioles 0.1–2.5 cm long, densely felted all around and villose with long stiff hairs on the upper side; blades elliptic, 3.7–14 x 1.8–6.8 cm, +/- symmetrical, acute to obtuse at base, acuminate at apex, strongly discolorous; upper side green, sparsely villose or rarely glabrescent, with stiff hairs 0.5–

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1 mm long, sometimes intermingled with sparse woolly hairs in the young stage; lower side whitish, densely felted and sometimes also with long stiff hairs on the midrib; secondary veins 7–17 on each side of midrib. Stipules opposite, free, interpetiolar, ovate

TAXONOMIC REVISION OF SABICEA SUBGENUS ANISOPHYLLAE

Phytotaxa 293 (1) © 2017 Magnolia Press • 25 to suborbicular, 5–10 x 4–12 mm, acute or obtuse, entire or shortly bilobed at apex, initially erect but soon reflexed, outside densely felted and sparsely villose at least on the margin, inside glabrous except for the base with short stiff hairs ca. 0.5 mm long. Inflorescences axillary on leafy stems, one per node, sessile, densely glomerulate, 1–2.5 cm in diameter, with 5–20 flowers. Bracts whitish outside, green inside, free, in 2 main pairs (sometimes with additional smaller bracts), elliptic to narrowly ovate, entire, acute to obtuse at apex, patent, 7–20 x 3–8 mm, outside densely white-felted and also sparsely villose with stiff hairs 1.2–2 mm long, inside villose with stiff hairs 1–1.5 mm long sometimes intermingled with very sparse woolly hairs; bracteoles narrowly ovate, entire and acute at apex, 5.5–7 x 1–1.5 mm, outside with same indumentum as the bracts, inside glabrous except for short hairs ca. 0.5 mm long at the base. Flower buds nearly cylindrical and only slightly enlarged at apex. Flowers sessile, 5-merous, heterostylous. Hypanthium with long silky and short woolly hairs intermingled. Calyx tube ca. 0.7 mm, densely white-felted with additional sparse long stiff hairs outside, glabrous inside; lobes narrowly triangular and acute, 3– 8 x 0.5–1 mm, patent, densely white-felted with additional sparse stiff hairs outside, glabrous or very sparsely villose inside; 1–2 tiny colleters between every pair of calyx lobes. Corolla white to pinkish-white; tube cylindrical, 8.5–11 x 1.5–2 mm; lobes triangular 3–4 x 1.5–2.3 mm; corolla pubescent outside (except the glabrous base of the tube) with intermingled short woolly and long silky hairs, the latter sometimes restricted to the apex of the lobes; mouth and distal half of tube sparsely pubescent inside with short multicellular hairs ca. 0.5 mm long. Stamens included, subsessile, attached around the middle of the tube in long-styled flowers, with tips exserted, filaments ca. 1 mm long attached near the mouth in short-styled flowers; anthers 2 x 0.4 mm. Disk cylindrical, ca. 0.6 mm long, glabrous. Style glabrous, ca. 13 mm long, exserted in long-styled flowers, ca. 6 mm long, included in short-styled flowers; stigmatic lobes 3 mm long in long-styled flowers, or 1.2 mm long in short-styled flowers, narrowly elliptic and +/- flat. Fruits red, flesh also red, ellipsoid, 5–7 x 4.5–5 mm when dry, sparsely pubescent with long silky and short woolly hairs intermingled (the latter +/- caducous), sessile. Seeds brown, polygonal, ca. 0.8 x 0.5 mm, reticulate.

Distribution: —Lake Victoria Regional Mosaic. Endemic to Burundi, where locally abundant ( Fig. 8 ).

Habitat and ecology: —Savannas and gallery forests; at 1300–2200 m altitude.

Phenology: —Flowers collected in March, May, and from August to January, probably flowering all year round. Fruits collected in March–May, July and October.

Discussion: — Sabicea becquetii resembles S. arborea and S. bequaertii , from which it can be distinguished by much the longer calyx lobes. It also differs in having the leaves usually villose above (rarely glabrescent, e.g. in Bouharmont 13179) and the bracts generally larger; see Table 2 for a summary of morphological differences. Furthermore, it has a different geographic range, the other two species are not known from Burundi.

The habit of Sabicea becquetii seems to be quite variable according to collectors notes, and needs further field study. It is apparently not a free-standing shrub, but rather a scrambling plant, which might start as a small shrub and become sarmentose as it gets older. The seeds of S. becquetii , which have been described as smooth by Hallé (1964), are in fact conspicuously reticulate ( Fig. 6 ).

Conservation status:— IUCN Red List Category: Vulnerable [VU B1ab(i,ii,iii,iv,v) + 2ab(i,ii,iii,iv,v)]. The extent of occurrence is estimated as 3868.579 km 2 and the area of occupancy as 80 km 2, both within the limit for Endangered under criteria B1 and B2. Based on herbarium records, the species is known from 15 subpopulations (sensu IUCN 2012), but 7 of them are likely to be extinct, and others are threatened. Only two populations are present in protected areas, namely the Bururi Forest Reserve and Kinoso Nature Reserve, both of which are very small in surface area. The species occurs in a densely populated region, where clearance of its habitat for agriculture represents the main threat; a decline in the extent of occurrence, area of occupancy, extent and quality of the habitat, number of locations (sensu IUCN 2012) and number of individuals can therefore be assumed. It qualifies as Vulnerable under conditions B1ab(i,ii,iii,iv,v) and B2ab(i,ii,iii,iv,v), and is likely to become Endangered in the near future.

Additional specimens examined:— BURUNDI. Munini (Mashuha, préfecture de Bururi), source de la Sikuvyaye , 22 September 1974, P. Auquier 4195 ( BR) ; Entre Bujumbura et Bugarama , 2 March 1980, J. Bouharmont 13179 ( BR) ; Rushubi , 2 January 1966, J. Lewalle 170 ( BR) ; Route entre Bururi et Makamba, 21 November 1966, J. Lewalle 1306 ( BR, MO) ; Kayanza: Route de Butara près de Ndora , 17 December 1967, J. Lewalle 2556 ( BR, MO) ; Kumuyange , 29 May 1971, J. Lewalle 5830 ( BR) ; Honga , 14 October 1971, J. Lewalle 6229 ( BR, MO) ; Buta , Bururi, 24 April 1953, G. Michel 4446 ( BR) ; Source du Nil, Bututsi , 5 March 1955, G. Michel 4686 ( BR) ; Makamba, 29 October 1980, P. Ndabaneze 1272 ( BR) ; Centre provincial de Makamba, à côté

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de l’école primaire, 20 December 2007, F. Niyongabo 44 ( BR) ; Réserve Naturelle Forestière de Bururi, 25 June 2004, F. Niyongabo 58 ( BR) ; Réserve Naturelle de Kinoso , 24 December 2007, F. Niyongabo 62 ( BR) ; Réserve forestière de Bururi, 28 July 2014, S. Ntore 777 ( BR) ; Nördlich von Mukayagoro , 7 March 1926, A. Peter 38402 ( BR, WAG) ; Munini , 22 September 1974, J. Rammeloo 4756 ( BR) ; Vallée Sikuvyaye , 28 August 1971, M. Reekmans 934 ( BR) ; Honga , 14 October 1972, M. Reekmans 1062 ( BR, MO) ; Vallée Siguvyaye , 20 September 1974, M. Reekmans 3577 ( BR) ; Vallée Siguvyaye , 31 December 1974, M. Reekmans 4054 ( BR, GH) ; Kwitaba , 19 October 1977, M. Reekmans 6532 ( BR, P, MO) ; Kwitaba , 15 December 1977, M. Reekmans 6824 ( BR, MO) ; Vyanda-Kigwena , 6 May 1982, M. Reekmans 11116 ( BR, MO, UPS, WAG) .

Figures

FIGURE 6. Variation of the seed-coat in Sabicea subg. Anisophyllae. A–B, Sabicea becquetii (Becquet 115); C–D, S. bequaertii (Troupin 12423); E–F, S. tersifolia (Lotter 1486); G–H, S. aurifodinae (Wieringa 5026); I–J, S. jacfelicis (Letouzey 9280); K–L, S. medusula (Letouzey 8469); M–N, S. mildbraedii var. glabrescens (Binot & Lejoly 147); O–P, S. sthenula (Cheek 11557); Q–R, S. sciaphilantha subsp. sciaphilantha (Sonké & Ikabanga 6182). Photos: Iris van der Beeten.

FIGURE 8. Distribution of Sabicea arborea, S. aurifodinae and S. becquetii.

FIGURE 11. Sabicea becquetii. A, flowering stem; B, flower; C, calyx lobe viewed from inside; D, hairs from the corolla mouth; E, anthers; F, style; G–H, placenta with ovules; I, fruit; J, placenta, the ovules removed; K, seeds. All details from Becquet 115. Drawing by N. Hallé, reprinted with permission from Hallé (1964: 401).