Sabicea floribunda var. paludosa 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 : 129-130

3c. Sabicea floribunda var. paludosa O. Lachenaud, Zemagho & Sonké , var. nov.

Holotypus: DEMOCRATIC REPUBLIC OF CONGO. Tshopo: Lilanda ( Yangambi ), 15.VIII.1940, fl., Germain 449 ( BR!; isotype: K!).

Ab alteribus varietatibus differt bracteis ± obovatis utrinque dense pubescentibus (nec orbicularibus, ovatis vel late ellipticis, glabris vel pilis sparsis munitis).

Etymology. – The epithet paludosa refers to the fact that this taxon is most commonly found in swamp and riverine forests, while other varieties usually grow on drained soils.

Distribution, ecology and phenology. – This taxon occurs in northeastern Gabon, and in D.R. Congo where it is found mostly in the central depression of the Congo basin (“cuvette congolaise”) with isolated records further east (Kivu) and south (near the border with Angola) ( Fig. 8 ). Its range closely approaches that of var. anisostegia in both Gabon and D.R. Congo. It grows mostly in swamp and riverine forest, but apparently also in secondary forest regrowth on drained soils, 350–1000 m in elevation.

Flowers have been recorded in January, from April to June and from August to October; fruits from April to October.

Conservation status. – The extent of occurrence (EOO) of S. floribunda var. paludosa is calculated to be 759,404 km ², well above the limit for “Vulnerable” status under subcriterion B1. Its area of occupancy is estimated to be 64 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 eastern Gabon and the Democratic Republic of Congo, and is known from 21 specimens representing 15 subpopulations, one of which occurs in a protected area (Kahuzi-Biega National Park in D.R. Congo). It is found in swamp forest and secondary forest regrowth, and appears to be not rare in its range. Given its ecology and wide distribution there is no evidence of a particular threat, and it is here assessed as Least Concern [LC] using the IUCN Red List Categories and Criteria ( IUCN, 2012).

Notes. – This taxon differs from other varieties by its more or less obovate and densely pubescent bracts (vs. orbicular, ovate or broadly elliptic, with indumentum sparse or absent) which are also usually narrower in proportion – hence a similarity with S. segregata , but that species does not occur in its range. In all other characters, especially leaves and indumentum, it comes very close to var. floribunda .

Paratypi. – DEMOCRATIC REPUBLIC OF CONGO. Bandundu : Iküma , 13.X.1948, fl., Jans 807 ( BR). Equateur : Ikelemba , VI.1934, fl., Dubois 423 ( BR); rte Bikoro-Inongo, km 27 , 17.X.1957, imm.fr., Evrard 2674 ( BR); rte Flandria-Makako (territoire Ingende ), 9.IV.1959, fl., Evrard 6054 ( BR); Bondombe, 9.IX.1942, buds, Hulstaert 843 ( BR); Lac Tumba-I.R.S.A.C. Mabali , 20.VI.1958, imm.fr., Thonet 221 ( BR, K). Kwango: entre Popokabaka et Kimabaka , près rivière Pumbu , 18.IV.1959, fl., Pauwels 2495 ( BR, P). Kwilu: vallée de la Djuma , VII.1902, imm.fr., Gentil s.n. ( BR); région de Bampumu, X.1922, fl., Vanderyst 12481 ( BR). Sud-Kivu: Kiaselela , territoire Shabunda , 19.IV.1959, imm.fr., A. Léonard 3900 ( BR, P). Tshopo: Opala , 15.VI.1949, imm.fr., Germain 5116 ( BR, WAG); Yabahondo ( rive gauche du Lomami ), 15.X.1952, fl. & imm.fr., Germain 8116 ( BR); Yangambi , 3.VI.1958, imm.fr., A. Léonard 759 ( BR, K); env. de Kisangani , à 3 km à l’E de Kabondo, 24.X.1977, buds, Lisowski 47453 ( BR, K); Kisangani, Kabondo , 6.V.1979, fl. (fallen), Lisowski 52401 ( BR, K); 20 km à l’W de Yangambi, 27.X.1938, fl., J. Louis 12110 ( BR). Tshuapa: Befale , IX.1934, imm.fr., Dubois 767 ( BR); Befale-Tolongote , 5.VI.1958, fl., Evrard 4185 ( BR, K, WAG). Sine loco: sine loco, s.d., fl., Pauwels 660 ( BR).

GABON. Ogooué-Ivindo: 10 km on road Malassa to Madouma, 8.I.2001, fl., Wieringa et al. 4028 ( LBV, WAG).

Figures

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).