Senegalia lötterii N. Hahn, N. Hahn, 2013

Hahn, Norbert, 2013, Senegalia lotterii (Fabaceae) a new species endemic to the Barberton Centre of Endemism, South Africa, Phytotaxa 119 (1), pp. 51-54 : 51-53

Senegalia lötterii N. Hahn , sp. nov. ( Fig. 1)

Differs from all southern African Senegalia species with paired prickles pointing straight ahead or slightly upwards one of which often fails to develop ( Fig. 2 ). The species is morphologically similar to the tropical species Acacia rovumae Oliver (1871: 353) differing from it by its fewer leaflets pairs per pinna 9–17 opposed to 13–31 and smaller pods 30–65 × 10–16 mm opposed to 70–150 × 17–25 mm. S. lotterii is geographically separated from A. rovumae by over 2000 km, ecologically S. lotterii is an edaphic specialist growing on ridges of ultramafic intrusions of the Barberton Centre of Endemism (van Wyk & Smith 2001) whereas A. rovumae is found in low altitude riverine forest and saline swamp forests of northern Mozambique, Tanzanian and Zambia (Ross 1975). S. lötterii having prickles in pairs differs from the S. senegal (Linnaeus 1753: 521) Britton (1930: 538) group which has its prickles in groups of three, the two outside ones being straight pointing ahead or slightly upwards, the central one downward.

Type:— SOUTH AFRICA. Mpumalanga: Opsaal , 25°40'04.476"S, 31°02'48.588"E, elev. 716 m, 29 December 2007 (fl), N . Hahn 2267 (holotype PRE!; isotype PRU!, ZPB!) .

Multi stemmed shrub, 3.5 m high bark grey smooth, young braches covered with lenticels. Stipules not spinescent in pairs filiform up to 2.5 mm long. Prickles in pairs often one being lost due to malformation, below the nodes, thorns almost straight light brown up to 6 mm long, pointing at 90°–110°. Leaves petiole 4.8–11.3 mm long, gland 2.2–3.4 mm long oblanceolate glabrous, rhachis 21.6–90.1 mm long, glabrous often with up to two glands between the upper pinna pairs, pinnae 3–12 pairs, rahillae 20.0– 36.9 mm long glabrous, leaflets 9– 17 pairs per pinna, 7.6–6.1 × 1.6–2.0 mm narrowly oblong, margins entire glabrous, glaucescent; apex obtuse to rounded, base oblique. Inflorescences spicate, abaxially situated. Flowers cream coloured, sessile spikes 30.1–45.5 mm long, glabrous; peduncle 10.1–16.4 mm long; calyx glabrous tube 1.7–1.9 mm long, lobes 0.8–1 mm long; corolla glabrous, tube 2.6–3.9 mm long, lobes 0.9–1.1 mm long, filaments 7.1–8.0 mm long; anthers 0.18–0.23 mm; ovary glabrous 1.18 × 0.31 mm long. Fruit a light brown pod, 30–65 × 10–16 mm.

Distribution and ecology:— Senegalia lotterii is presently only known from the near vicinity of its type locality falling within the Barberton Centre of Endemism, an area noted for its high percentage edaphic endemics (van Wyk & Smith 2001) ( Fig. 3 ). Senegalia lotterii grows in “ Acacia ” dominant open bush land, on poorly drained clay soils derived from ultramafic intrusions (Anhaeusser 2006).

Diagnostics and relationship:— Acacia chariessa Milne-Redhead (1933: 143) sensu Lötter (2002) was thought to belong to the A. ataxacantha De Candolle (1825: 459) group. The A. ataxacantha group is characterised by woody plants armed with simple, recurved prickles scattered irregularly along the internodes and by having spicate inflorescence. Senegalia lotterii differs from the above mentioned group by its thorns being in pairs one of which is often lost due to malformation, thus being confused with the A. ataxacantha group. The almost straight thorns of S. lotterii pointing at 90°–110° is an unique feature not found in the biprickled species of South Africa. Within this region the only species of Senegalia sharing this feature is S. senegal differing from S. lotterii in being a tri-prickled species with its two outside thorns being straight pointing ahead or slightly upwards and the central one downward.

Etymology:—The author has the honour of naming this species after Mervyn Lötter who was the first to discover the plant and pronounce its existence.

Additional specimen examined (paratype):— SOUTH AFRICA. Mpumalanga; Mundt’s Concession , 6 April 2001 (fl), P . J . D. Winter et al. 4758 ( PRE) .

Figures

FIGURE 2: Characteristic thorns of Senegalia lotterii with the upper malformed and the lower projecting at 110°.

FIGURE 3: Distribution of Senegalia lotterii.