Diospyros silicea G.E. Schatz, Lowry & Phillipson, 2020

Schatz, George E., Lowry Ii, Porter P. & Phillipson, Peter B., 2020, Taxonomic studies of Diospyros (Ebenaceae) from the Malagasy region. V. Synoptic revision of the Bernieriana group in Madagascar and the Comoro Islands, Candollea 75 (2), pp. 203-218 : 212

5. Diospyros silicea G.E. Schatz, Lowry & Phillipson , sp. nov.

( Fig. 4 ).

Holotypus: MADAGASCAR. Region Atsimo-Andrefana [Prov. Toliara]: forêt de Zombitsy (= Zombitse-Vohibasia) ( Sakaraha ), [22°52'52"S 44°41'22"E], 600 – 850 m, 26 – 29.III.1955, fr., Humbert, Bégué & Capuron 29598 ( P [ P03974999 ]!; iso-: G [ G00341735 ]!, MO-6956010 !, P [ P00722704 ]!, TAN!, W!).

Diospyros silicea G.E. Schatz, Lowry & Phillipson can be distinguished from other members of the Bernieriana group by its leaves with distinctly undulate margins and its ellipsoid fruit with the apex exserted above the calyx.

Tree 5–10 m tall. Young stems initially covered with erect, very short (<0.1 mm) gray trichomes, glabrescent. Leaves 2.4–7.8 × 1.2–2.7 cm, elliptic, glabrous above and below, base cuneate, margin distinctly undulate and somewhat revolute, apex acute to acuminate with the tip rounded, midrib slightly impressed above, raised below, venation weakly brochidodromous with 6 secondary veins per side, slightly raised and faintly visible above, completely obscure below; petiole 3–7 mm, 0.7 mm diam., canaliculate, initially covered with very short (<0.1 mm), semi-erect white trichomes, glabrescent. Male flowers in fascicles of 3 or 4 in axils of leaves, ellipsoid, 4 – 5 mm long, 2.5– 3 mm in diam. in bud; pedicels 1 mm long, 0.5 mm in diam, covered with very short (<0.1 mm) erect, white trichomes, bearing several caducous bracts; calyx tubular, 4–5 mm long, 2–3 mm in diam., the apex with irregular shallow lobes, densely covered very short (<0.1 mm) semi-appressed, white trichomes and the surface papillate outside, glabrous inside; corolla tubular, 7.5 mm long, 2.2 mm in diam., basal half glabrous, distal half densely covered with very short (0.1 mm) appressed trichomes, lobes 5, 3 × 1.5 mm, narrowly ovate, imbricate, adaxially concave, densely covered with white, appressed trichomes c. 0.1 long outside, glabrous inside; stamens 10, adnate to corolla at the base, filaments 0.5– 0.8 mm, anthers 2– 2.2 mm. Female flowers not seen. Pedicel in fruit 2–3 mm long, to 4–5 mm in diam., covered with very short (<0.1 mm) semi-appressed white trichomes; calyx extending 5–6 mm above fruit, apex with shallow irregular lobes, not completely enclosing the fruit, i.e., the apex of the fruit visible before the calyx lobes break off, glabrous outside, densely covered with very short (<0.1 mm) erect, white trichomes inside. Fruit 15–18 mm long, 9–14 mm in diam., ellipsoid, the apex exserted above the calyx, glabrous to densely covered toward the apex with short (<0.1 mm), appressed, light golden trichomes, crowned by the style/stigma remnant, cone-shaped, 2 mm tall, 1 mm in diam. at base.

Etymology. – The species epithet refers to the weathered siliceous sand substrate where the new species occurs.

Distribution and ecology. – Diospyros silicea is known from only two gatherings in subarid forest and thicket on siliceous sand from Zombitse-Vohibasia National Park south to Tsiombe ( MADAGASCAR CATALOGUE, 2020), at an elevation of 250– 850 m.

Conservation status. – Diospyros silicea has a restricted geographic range in the form of an AOO of 8 km ². It is present from the Zombitse-Vohibasia National Park. At its other known locality, east of Tsiombe, it is threatened by grazing, fire, and exploitation for firewood and construction material, all of which are projected to result in continuing decline. With respect to the principal threat of grazing, it exists at two locations. Therefore, D. silicea can be assessed for its risk of extinction as “Endangered” [EN B2ab(iii)].

Notes. – The two collections Humbert et al. 29598 and Service Forestier 11918 represent a single gathering divided between two separate collection series. Diospyros silicea can be distinguished from other members of the Bernieriana group by its leaves with distinctly undulate margins, and its ellipsoid fruit exserted above the calyx with shallow irregular lobes.

Paratypi. – MADAGASCAR. Reg. Androy [Prov. Toliara]: env. E de Tsiombe, [25°18'45"S 45°30'15"E], 70 m, 14.XI.1967, buds, Service Forestier 27981 ( MO, P, TEF). Reg. Atsimo-Andrefana [Prov. Toliara]: forêt de Zombitsy , à l’Est de Sakaraha , [22°52'52"S 44°41'22"E], [600–850 m], III.1955, fr., Service Forestier 11918 ( G, MO, NY, P [2 sheets], TEF, US).

Figures

Fig. 4. – Diospyros silicea G.E. Schatz, Lowry & Phillipson. A. Flowering branch; B. Fruiting branch; C. Fruit; D. Detail of leaf venation (adaxial surface). [A: Service Forestier 27981, P; B–D: Service Forestier 11918, P] [Drawing: Alain Jouy]