Sabicea floribunda var. anisostegia O. Lachenaud, Zemagho & Sonké, 2020

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 : 129

3b. Sabicea floribunda var. anisostegia O. Lachenaud, Zemagho & Sonké , var. nov.

( Fig. 1E–F ).

Holotypus: CAMEROON. Reg. East: près Yenga Port Gentil , village situé à 35 km au NNE de Moloundou, 21.IV.1971, fl., Letouzey 10716 ( BR!; isotype: K!, P!, YA!) .

Ab alteribus varietatibus differt bracteis valde inaequales majoribus in inflorescentia dispersis (nec bracteis superioribus gradualiter minoribus quam inferioribus).

Etymology. – The varietal epithet anisostegia refers to the bracts of very unequal sizes, which are the main diagnostic character of this taxon.

Distribution, ecology and phenology. – This variety occurs from southeastern Cameroon to southwestern D.R. Congo, and disjunctly in eastern D.R. Congo ( Fig. 8 ), but is mostly absent from the central depression of the Congo basin (“cuvette congolaise”) where replaced by var. paludosa . Its range closely approaches that of the latter in both Gabon and D.R. Congo, and locally overlaps that of var. floribunda in Gabon. It is found in forest edges and regrowth, 180–1250 m in elevation.

Flowers have been recorded from October to January and April to July, probably all year; fruits from January to July and in September-October, probably all year as well.

Conservation status. – The extent of occurrence (EOO) of S. floribunda var. anisostegia is calculated to be 1,349,092 km ², well above the limit for “Vulnerable” status under subcriterion B1. Its area of occupancy (AOO) is estimated to be 124 km ², which falls within the limit for “Endangered” status under subcriterion B2, but is an obvious underestimation, given the low collecting density in most of its range. The taxon occurs in Central Africa from Cameroon to the Democratic Republic of Congo, where it grows in secondary forest, and is known from 40 specimens. Its situation is rather comparable to that of the species as a whole, and it is assessed as “Least Concern” [LC] using the IUCN Red List Categories and Criteria ( IUCN, 2012) for the same reasons.

Notes. – This is the most distinctive variety of S. floribunda , and further work may show it to be specifically distinct. It is best recognised by the arrangement of the bracts in the inflorescence: var. anisostegia has a few large bracts occurring at scattered nodes and the remainder much smaller, while in other varieties the bracts are more or less gradually decreasing in size from lower to upper nodes (except the lowest pair, which is often smaller than those above it). It is also usually more hairy than other varieties, especially on the stems.

Paratypi. – ANGOLA. Cabinda : near the village Caio in the Hombe country , 9.I.1917, fl. & imm.fr., Gossweiler 7665 ( BM, K).

CAMEROON. Reg. Central: Réserve forestière Mbalmayo , 15.IV.1967, fl., Mezili 80 ( BR, P); Atotzok , 1953, fl. & imm.fr., Surville 312 ( YA). Reg. East: 22 km E of Lomié, 12.II.1977, fr., Lowe 3149 ( K, YA) ; Near Echiambor , 18.II.1977, fr., Lowe 3500 ( YA) ; Nkamouna, 11.VI.2004, fl., Sonké 3481 ( BR, BRLU) ; ibid. loco, 11.VI.2004, fr., Sonké 3482 ( BR, BRLU) ; Mbalam II: Mbarga , 24.VI.2008, fl., Sonké 4943 ( BR). Reg. South: Bitye , 1917, fl., Bates 885 ( BM) ; Bitye, 1917, buds, Bates 1120 ( BM) ; à l’W d’Alati (100 km SE de Djoum), 12.I.1973, imm.fr., Letouzey 11832 ( BR, P, YA).

DEMOCRATIC REPUBLIC OF CONGO. Ituri: Ituri , Lodjo , near AGK mining camp , 25.I.2011, imm.fr., Bytebier et al. 3343 ( BR); Ituri , mont Hoyo , 2.VIII.1975, imm.fr., Lisowski 40879 ( BR). Kongo Central: Kimuenza, X–XI.1900, fl., Gillet 1749 ( BR); Entre Luzumu et Sanda , vallée de la Ma Ngo , 25.II.1965, fr., Pauwels 4905 ( BR). Nord-Kivu: entre Walikale et Kalehe ( Kivu ), III.1932, fl. & imm.fr., Lebrun 5267 ( BR, WAG); Rte Kavumu-Walikale, vers km 110, env. d’Irangi , 11.III.1960, fr., Troupin 12067 ( BR). Tshopo: km 58 , rte de Kisangani vers Ubundu (rive gauche), 6.IV.1977, fr., Lejoly 1278 ( BR, BRLU); rte Kisangani-Ubundu, km 58 , 7.IV.1977, fr., Lisowski 44605 ( BR, K).

GABON. Haut-Ogooué: 5 km rte Moanda-Bakoumba, 16.IX.1970, fr., F.J. Breteler 6475 ( BR, K, LBV, P, WAG); de Zanaga à Franceville , 21.X.1954, fl., Trochain 9099 ( P). Ogooué-Ivindo: 7 km N of km 49 Makokou-Mekambo road which is bifurcation with Bélinga road, near Djadie R. , 15.XI.1977, fl., Leeuwenberg 11545 ( BR, K, P, WAG); Babièl-Nord ridge , 4 km from camp Bélinga, X.1987, fl., A.M. Louis et al. 2312 ( BR, LBV, WAG); Rte de Babiel Nord , few km W of Belinga, 18.VII.1985, fl. & imm.fr., Bos et al. 10658 ( BR, K, LBV, P, WAG) ; Bélinga, 9.VI.1978, fr., Florence 1217 ( P); Belinga , 25.VII.1981, fr., Gentry 33569 ( P) ; piste du Bouéni , 20 km SE Makokou, 11.II.1961, fr., N. Hallé 1130 ( K, P) ; 7 km NE Makokou, 11.III.1961, fr., N. Hallé 1454 ( P) ; Bélinga , 26.X.1964, fl., N. Hallé 2804 ( K, P); ibid. loco, 28.X.1964, buds, N. Hallé 2866 ( BR, P); ibid. loco, 31.X.1964, fl. & fr., N. Hallé 2951 ( BR, K, P); ibid. loco, 11.XI.1964, buds, N. Hallé 3126 ( P); ibid. loco, 1.I.1980, fl., Pierre-Baltus 98 ( P); 25 km on road Mékambo to Madjingo, 27.XII.2000, fl., Wieringa et al. 3648 ( BR, LBV, WAG). Ogooué-Lolo: Chantier Bambidie, c. 52 km on the road to Okondja-Lelama, along Sebe river , 31.X.2005, fr., Sosef et al. 2123 ( LBV, WAG). Woleu-Ntem: behind the WWF-station , at entrance to Bordamur consession area , 8.X.2002, fr., Strijk 54 ( WAG); ibid. loco, 1 km from Assock Begue, 8.X.2002, fl., Strijk 59 ( LBV, WAG).

REPUBLIC OF CONGO. Bouénza: forêt de la Bouénza , piste de l’Espérance du village de M’Boumou vers la Bouénza , 16.XI.1964, buds, Bouquet 757 ( P). Sangha: West slope of Mt. Nabemba , 15.XI.1991, buds, Thomas et al. 8892 ( WAG).

Figures

Fig. 1. – Seeds of Sabicea spp. viewed in electron microscopy. Sabicea couteronii O. Lachenaud, Zemagho & Sonké: A. Entire seed; B. Detail of seed surface. Sabicea dichrosepala O. Lachenaud, Zemagho & Sonké: C. Entire seed; D. Detail of seed surface. Sabicea floribunda var. anisostegia O. Lachenaud, Zemagho & Sonké: E. Entire seed; F. Detail of seed surface. Sabicea nobilis R.D. Good: G. Entire seed; H. Detail of seed surface. [A–B: Sonké & Zemagho 6334; C–D: Dessein et al. 2028; E–F: N. Hallé 2951; G–H: Sosef et al. 2529] [Photos: I. van der Beeten]

Fig. 8. – Distribution map of Sabicea floribunda K. Schum. (squares: var. anisostegia O. Lachenaud, Zemagho & Sonké; stars: var. floribunda; triangles: var. paludosa O. Lachenaud, Zemagho & Sonké; circles: var. paucinervis Wernham).