Sabicea proselyta (N. Hallé) Razafim. et al.

Lachenaud, Olivier, Zemagho, Lise & Sonké, Bonaventure, 2020, A synopsis of the Sabicea floribunda group (Rubiaceae) from Central Africa, including three new species, Candollea 75 (1), pp. 115-143 : 133-134

5. Sabicea proselyta (N. Hallé) Razafim. et al. in Taxon 57: 20. 2008

( Fig. 2A–B , 7E–F ).

≡ Pseudosabicea proselyta N. Hallé in Adansonia ser. 2, 3: 172. 1963.

Holotypus: GABON. Estuaire: Nkoulounga , 11.VII.1959, N. Hallé 748 ( P [ P00077595 ]!).

Distribution, ecology and phenology. – Sabicea proselyta occurs in southern Cameroon, Equatorial Guinea ( Rio Muni), western and central Gabon (but not in the lower Ogooué basin) and the Mayombe range in southwestern Republic of Congo ( Fig. 10 ). It grows in secondary forest, edges and regrowth, on drained soils or sometimes along rivers, 50–1080 m in elevation.

Flowers have been collected in April, June-July and November; fruits in January (immature), February to May (mature), July (immature) and November (mature).

Conservation status. – The extent of occurrence (EOO) of S. proselyta is calculated to be 162,301 km ², well above the limit for Vulnerable status under subcriterion B1. Its area of occupancy (AOO) is estimated to be 92 km ², within the limit for “Endangered” status under criterion B2, but is evidently underestimated because most of its range is not well prospected. The species occurs in Central Africa from south Cameroon to the Congo Republic, and is known from 28 specimens representing 22 subpopulations. It occurs in four protected areas, the Monte Alén National Park in Equatorial Guinea, Waka and Doudou Mountains National Parks in Gabon, and Dimonika Biosphere Reserve in the Republic of Congo. Most of its range is sparsely populated, and because it is a plant of forest edge habitats, it is likely to benefit from small-scale forest clearing, e.g. that induced by selective logging. As a result there is no evidence of a particular threat, and the species is here assessed as “Least Concern” [LC] using the IUCN Red List Categories and Criteria ( IUCN, 2012).

Notes. – Although the protologue ( HALLÉ, 1963) does not specify in which herbarium the type of S. proselyta was deposited, this collection has only one sheet in P, which is therefore considered as the holotype.

Probably because Sabicea proselyta has no very striking characters, it has often been confused with its relatives S. couteronii , S. dichrosepala , S. rubiginosa and S. sanguinosa . The differences between them are summarised in Table 1 . Among the 18 Gabonese specimens cited as Pseudosabicea proselyta by SOSEF et al. (2006), only nine are correctly identified; six belong to S. rubiginosa (Breteler 9576; Haegens 222; van Nek 128 & 190; Wieringa 2389; J.J.F.E. de Wilde 9688), one to S. dichrosepala (J.J.F.E. de Wilde 284) and two to S. sanguinosa subsp. sanguinosa (Sosef 1613, 1745). Another collection from the Republic of Congo, Kimpouni 600, cited by LACHENAUD (2009) as Pseudosabicea proselyta , actually represents S. couteronii . The two collections from the Republic of Congo cited here are therefore the first authentic records of S. proselyta from this country.

The indumentum of the lower leaf surface is usually appressed in this species, but in two collections (J.J.F.E. de Wilde 7762 from Cameroon and van Valkenburg et al. 3140 from Gabon) it is mostly erect with appressed hairs restricted to the veins. These collections match S. proselyta in other characters and are therefore regarded as conspecific.

Additional material studied. – CAMEROON. Reg. South: station du Cacaoyer de N’koemvone , S. of Ebolowa, 14 km on the road to Ambam, 28.XI.1974, fl. & fr., J.J.F.E. de Wilde 7762 ( BR, K, P, WAG, YA); E Sangmelima , 16.V.2016, fr., Sonké & Zemagho 6329 ( BR, BRLU, K, MO, WAG, YA); Campo Ma’an area , Onoyong , in the National Park , 20.III.2001, imm.fr., Tchouto Mbatchou et al. ONOX 93 ( WAG).

EQUATORIAL GUINEA. Centro-Sur: Monte Alen, 25.III.1997, fr., Ngomo 78 ( BRLU); Monte Alen, Transecto 3,900 m del transecto, 21.VII.1998, imm.fr., Ngomo & Ndong 368 ( BRLU); PN de Monte Alen , dalle rocheuse d’Engong , 5 km à l’W du village d’Engong, 12.V.2002, fr., Parmentier & Esono 2780 ( BRLU); PN de Monte Alen-transect de Monte Chocolate , 8.I.1998, imm. fr., Van Reeth 141 ( BRLU). Litoral: Rte de Nco vers Misobong au niveau de la grande cascade , 9.I.1998, imm.fr., N. Nguema & Lejoly 202 ( BRLU). Wele-Nzas: entre Nsuamayong et inselberg Akuom , 23.I.1998, imm.fr., Obama & Lejoly 656 ( BRLU).

GABON. Estuaire: km 18 Kougouleu-Kouamé road , 15.XI.1982, fl., Leeuwenberg 12511 ( BR, K, LBV, WAG); km 13 Tchimbélé-Kinguélé , 7.II.2008, fr., Dessein et al. 1747 ( BR, LBV, WAG); Monts de Cristal, 5 km de Kinguélé, 18.I.1968, imm.fr., N. Hallé & Villiers 4540 ( P); Crystal Mountains , 250 m on transect D 4, 25.XI.2000, fl., N. Nguema 1459 ( BR, LBV, WAG). Moyen-Ogooué : Mboumi , 16.II.2000, imm.fr., Champluvier 6163 ( BR, K); c. 10 km NNW of Ndjolé, on BSO forestry road , 26.II.2008, fr., Dessein et al. 2150 ( BR, LBV, WAG); C.E.F.A. Ayem , 10 km SW Ndjolé, 29.IV.1963, fr., N. Hallé 1918 ( K, P); ibid. loco, 29.IV.1963, buds, N. Hallé 1918bis ( BR, K, P); ibid. loco, 30.IV.1963, fl., N. Hallé 1955 ( K, P); ibid. loco, 8.V.1963, fr., N. Hallé 2022 ( P); Abanga , chantier CEFA , 1.VI.1963, fl., N. Hallé 2126 ( P). Ngounié : Parc national de Waka , 1°10'34"S 11°08'02"E, 28.XI.2007, imm. fr., Boussengui-Nongo et al. 312 ( LBV); Ovala, 16.V.1963, fr., N. Hallé & Cours 5937 ( P). Nyanga : chantier SFN , 28.XI.2003, fl. & imm.fr., van Valkenburg et al. 2646 ( BR, K, LBV, P, WAG). Ogooué-Maritime : logging road CBG concession eastward of Peni , 20.IV.2005, fr., van Valkenburg et al. 3140 ( BR, K, WAG). Woleu-Ntem : 15 km SE of Mitzic, FOREENEX forest exploitation , road from FOREENEX forestry camp to Madouaka village , 7.XI.2009, fl., Bissiengou et al. 752 ( LBV, WAG).

REPUBLIC OF CONGO. Kouilou: rte de Dimonika à Pounga , 24.XI.1978, fl., Cusset 514 ( P). Niari : Col du Bamba , 6.I.1969, imm.fr., Attims 58 ( P).

Figures

Fig. 2. – Seeds of Sabicea spp. viewed in electron microscopy. Sabicea proselyta (N. Hallé) Razafim. et al.: A. Entire seed; B. Detail of seed surface. Sabicea rubiginosa O. Lachenaud, Zemagho & Sonké: C. Entire seed; D. Detail of seed surface. Sabicea sanguinosa subsp. sanguinosa: E. Entire seed; F. Detail of seed surface. Sabicea segregata Hiern: G. Entire seed; H. Detail of seed surface. [A–B: van Valkenburg et al. 3140; C–D: Lachenaud et al. 2105; E–F: A. M. Louis & Reitsma 2004; G–H: J.J.F.E. de Wilde et al. 9485] [Photos: I. van der Beeten]

Fig. 7. – Sabicea floribunda var. floribunda: A. Inflorescence. Sabicea floribunda var. paucinervis Wernham: B. Fruits. Sabicea nobilis R.D. Good: C. Lower side of leaf; D. Stem with mature infructescence. Sabicea proselyta (N. Hallé) Razafim. et al.: E. Fruiting stem; F. Mature infructescence. [A: near Tchimbélé, Gabon, plant not collected; B: Sonké 5915; C–D: Texier et al. 706; E: Sonké & Zemagho 6329; F: van Valkenburg et al. 3140] [Photos: A: S. Dessein; B: B. Sonké; C–D: N. Texier; E: B. Sonké; F: J. Degreef]

Fig. 10. – Distribution map of Sabicea proselyta (N. Hallé) Razafim. et al. (circles), S. rubiginosa O. Lachenaud, Zemagho & Sonké (stars) and S. sanguinosa (N. Hallé) Razafim. et al. (triangles: subsp. sanguinosa; squares: subsp. viridis O. Lachenaud, Zemagho & Sonké).