Drypetes stevartii Sonke & Quintanar, 2023

Quintanar, Alejandro, Sonke, Bonaventure, Simo-Droissart, Murielle, Barbera, Patricia, Libalah, Moses & Harris, David J., 2023, A matter of warts: a taxonomic treatment for Drypetes verrucosa (Putranjivaceae, Malpighiales) and a new cauliflorous species from Cameroon and Nigeria, D. stevartii, Plant Ecology and Evolution 156 (2), pp. 160-173 : 160

Drypetes stevartii Sonke & Quintanar sp. nov.

Figs 2 , 3 , 4

Type.

CAMEROON • [Littoral] Binoum ; 4°12'N, 11°02'E; 22 Dec. 2022; fr.; B. Sonké & M. Simo 7127; holotype: YA; isotypes: BR, BRLU, E, K, MA [ MA 959269 ], MO, P .

Diagnosis.

Haec species a Drypete verrucosa Pierre ex Hutch. stipulis 1.9-2.2 mm longis anguste triangularibus caducis, petiolis (2.6-)3-4.6(-5.1) mm longis confertim subtiliter rugosis, laminis foliorum (6.5-)7-11.1(-13.7) cm longis ad basim plerumque obliquis aliquando asymmetricis subter pubescentibus imprimis in nervis, inflorescentiis in truncum et ramorum principalium positis constantibus ex 1-7(-18) floribus, pedicello florum masculinorum (9.2-)14.7-20 mm longo, sepalis florum masculinorum 4.7-4.9 mm longis, disco florum masculinorum 3.1-3.3 mm diametro aliquantum exili sparsim pubescenti, staminibus 19-20, filamento 1.5-1.6 mm longo, anthera 2.2-2.4 mm longa anguste ellipsoidea sparsim pubescenti, pedicello florum femininorum 5.5-6.2 mm longo, sepalis florum femininorum 2.6-3.2 mm longis, disco florum femininorum 2.1-2.4 mm diametro glabro, fructibus (18-)20-29(-31) × 17-23(-25) mm late ovoideis, exocarpio 1-3 mm lato phymatodeo brunneo diluto luteolo tum aurantiacescenti vel rubescenti differt.

Description.

Tree up to 20 m tall, with plagiotropic sinuous branches; trunk up to 20 cm in diameter, fluted; bark greenish-brown, smooth, rough and flaking off when old, slash light brown, later dark brown; young branchlets subterete, slightly sulcate, dark-coloured when dry, sparingly and shortly pubescent, glabrescent, trichomes 0.1-0.3 mm; terminal buds scaly, scales 1.8-2.8 × 0.7-2 mm, ovate, firm, slightly keeled, shortly pubescent outside with trichomes 0.1-0.3 mm, glabrous inside, ciliate, cilia 0.1-0.3(-0.5) mm. Leaves: stipules 1.9-2.2 × 0.5-0.9 mm, narrowly triangular, sparsely and shortly pubescent outside, glabrescent, trichomes 0.2-0.3 mm, glabrous inside, sparingly ciliate near the base, cilia 0.2-0.4 mm, caducous; petiole (2.6-)3-4.6(-5.1) mm long, (0.9-)1.1-1.6(-1.8) mm in diameter, finely transversely wrinkled, sparsely and shortly pubescent, glabrescent, old ones slightly blistered, trichomes 0.1-0.4 mm; blade (6.5-)7-11.1(-13.7) × (2.8-)3-5.8(-6.4) cm, elliptic, papery to subcoriaceous, base acute, sometimes slightly obtuse, oblique, sometimes asymmetrical, rounded on one side, basal sides usually meeting the petiole at the same point, margin crenulate-serrulate for most of its length, crenulae/teeth 0.1-0.6 mm, acute, frequently blunt, flat to slightly recurved near the blade base, shortly acuminate, apex 4-8 mm, abaxial surface between the nerves glabrous; midrib smooth, slightly longitudinally wrinkled when dry, glabrous; first order lateral veins 5-8 pairs, ascending, more or less regularly spaced, slightly depressed above, prominent beneath, courses curved and anastomosing well within the margin, oriented at (55-)60-73(-77)° to the midrib, glabrous; second order venation loosely reticulate, hardly or not raised above, slightly so beneath. Male inflorescence borne on small cushion-like excrescences of the trunk and main branches (categories I and II), in clusters of (1-)3-7 flowers; bracts 0.7-0.8 × 0.5-0.9 mm, ovate to suborbicular, minutely pubescent outside, glabrous inside, minutely ciliate, trichomes and cilia 0.1-0.2 mm, barely distinguishable. Male flowers pedicellate, yellowish green or brownish green; pedicel (9.2-)14.7-20 mm long, 0.5-0.9 mm in diameter, slender, very sparingly and shortly pubescent, trichomes 0.1-0.2 mm; sepals 5-6, 4.7-4.9 × 4.2-5.1 mm, widely ovate, acute, cucullate, imbricate, the outer often smaller than the inner, glabrous outside and inside, margin minutely ciliate for most of its length, cilia 0.1-0.2 mm; stamens 19-20, one-whorled, surrounding the disc, more or less enveloped by its marginal lobes, filaments 1.5-1.6 mm, white, anthers 2.2-2.4 mm long, 0.6-0.8 mm in diameter, narrowly ellipsoid, sub-basifixed, introrse, pale yellow, sparsely pubescent, trichomes 0.1-0.2 mm; disc ca 0.2 mm high, 3.1-3.3 mm in diameter, rather flat, thin, rugose, sparsely and minutely pubescent, trichomes to 0.1 mm, pistillode to 0.4 mm, laminate, 3-branched. Female inflorescence borne on small cushion-like excrescences of the trunk and main branches (categories I and II), in clusters of 1-7(-18) flowers; bracts 0.7-1.1 × 0.5-0.6 mm, otherwise similar to the male ones. Female flowers pedicellate, yellowish green or brownish green, sometimes pinkish; pedicel (5.5-)12-26 mm long, 0.5-0.9 mm in diameter, more or less robust, very sparingly and shortly pubescent, trichomes 0.1-0.2 mm; sepals 5-6, 2.6-3.2 × 2.5-3.4 mm, otherwise similar to the male ones; disc 0.2-0.3 mm high, 2.1-2.4 mm in diameter, concave, cupulate, fleshy, glabrous; style 1, sessile, unbranched; stigmas 3, obdeltoid, stigmatic surface ca 0.5 mm long, 1.1-1.2 mm wide; ovary 1.3-1.4 mm long, 2-2.2 mm in diameter, subglobose, 3-celled, densely and minutely pubescent, trichomes 0.1-0.2 mm. Fruits (18-)20-29(-31) mm long, 17-23(-25) mm in diameter, widely ovoid, with caducous sepals and stigmas, exocarp warty, yellowish brown turning orange or red when ripe, shortly pubescent, trichomes 0.1-0.4 mm, mesocarp 1-3 mm thick when dried, hard, endocarp 0.8-1.3 mm thick, bony, 3(-4)-seeded; seeds ca 16.8 mm long, ca 17.2 mm in diameter; fruiting pedicel (15-)21-39(-42) mm long, 1.7-3.6 mm in diameter, very sparingly and shortly pubescent, trichomes 0.1-0.2(-0.4) mm.

Distribution and chorology.

Cameroon (Centre, East, Littoral, and West Regions) and eastern Nigeria (Adamawa) (Fig. 2 ). Lower Guinea subcentre of endemism ( White 1979).

Habitat.

Primary or secondary evergreen and semi-deciduous forests; at 230-620 m a.s.l.

Phenology.

Flowering specimens were collected in October and November, and fruiting specimens from November to April.

Etymology.

According to the wishes of Bonaventure Sonké, the collector of the type specimen, we have named this new species after the botanist Tariq Stévart (b. 1974, Coordinator, West and Central Africa Program, Missouri Botanical Garden, Africa & Madagascar Department), in recognition of his helpful collaboration to our research on Drypetes and especially of his constant support to the second and third authors.

Preliminary IUCN conservation assessment.

Drypetes stevartii is known from 26 gatherings representing 24 occurrences and three to seven subpopulations. The extent of occurrence (EOO) is estimated to be 88,152 km2, far exceeding the upper limit for Vulnerable under subcriterion B1, whereas the area of occupancy (AOO) is estimated to be 60 km2, which falls within the limits for Endangered under subcriterion B2. One occurrence is located within the Gangume Forest Reserve in Nigeria (one location), five others are located within the Mpem et Djim National Park in Cameroon (one location), while the two occurrences located at Bilangue and Kikot do not appear under threat (one location). The rest of the occurrences are located outside of protected areas and are threatened by small-scale shifting agriculture (5 locations), industrial sugar plantations (one location), logging (located in a logging concession, representing one location), and quarrying for a dam project (one location). These activities indicate a decline in the quality and extent of the habitat of the species. With regard to the most serious plausible threat (shifting agriculture), the 24 occurrences represent 11 locations (sensu IUCN Standards and Petitions Committee 2022), which is just more than the upper limit for Vulnerable under the condition ‘a’ of subcriterion B2. We consider that habitat loss will continue in the near future, leading to the disappearance of the 5 occurrences threatened by quarrying. These future disappearances will thus lead to a continuing decline in AOO, number of locations, and mature individuals. Drypetes stevartii is therefore assessed as Near Threatened (NT).

Additional material examined.

CAMEROON - Centre • Goura; [4°33'N, 11°24'E]; Nov. 1938; fr.; H. Jacques-Félix 2383; P [P04765168, P04765171, P04765172, P04765173] • Goura, entre Bafia et Ntui; [4°33'N, 11°24'E]; fl. ♂; B. Mpom 520; P [P04707491], YA [YA0029435] • Mindou; 5°10'N, 11°35'E; 20 Jan. 2020; fr.; B. Sonké & M. Simo 6398; YA • Mpem et Djim, Malabo, plot Mpem 001, tag 245; 5°01'N, 11°39'E; 14 Feb. 2019; fr.; IRD plot 2354 (B. Sonké & al.); BRLU, YA • Parc National du Mpem et Djim; 5°08'N, 11°32'E; 12 Dec. 2022; fr.; F. Nzoyeuem & H. Leblanc 158; BR, BRLU, MA, MO, YA • Parc National du Mpem et Djim, Kounoungou; 5°02'N, 11°37'E; veg.; 24 Mar. 2023; B. Sonké & al. 7267; BR, BRLU, MO, YA • Parc National du Mpem et Djim, Kounoungou; 5°01'N, 11°36'E; fr.; 27 Mar. 2023; B. Sonké & al. 7303; BR, BRLU, MO, P, YA • Vers Biakoa à 117 km de Ntui ; [4°33'N, 11°28'E]; 18 Nov. 1969; fr.; B. Mpom 535; P [P04707489, P04707490], YA [YA0029434] • Versant septentrional des monts Meiki (983 m) au Sud de Ndo (25 km NNE d’Esse); [4°19'N, 11°58'E]; 9 Nov. 1969; fl. ♀, fr.; R. Letouzey 9543; BR [BR0000015776754], COI, P [P04707446], YA, WAG [WAG.1564736]. - East • 60 km south of Yokadouma , 30 km after Ngato, 15 km after river, ALPICAM 'base de vie’, then on forestry road starting 4 km before Masea village ; 3°09'N, 14°44'E; 4 Mar. 2019; fr.; T.L.P. Couvreur & al. 1194; YA . - Littoral • Bilangue; 4°10'N, 11°00'E; 29 Apr. 2022; fr.; B. Sonké & al. 6975; BR, BRLU [BRLU0032163], K, MO, P, WAG, YA • Bindamongo, km 106.5 sur route Yaounde-Bafia , à 15 km WNW de Ntui; [4°31'N, 11°30'E]; 18 Nov. 1969; fl. ♂; R. Letouzey 9568; BR [BR0000015776730], P [P04707231], YA [YA0029469] • Bindamongo , km 106,5 sur route Yaounde-Bafia , à 15 km WNW de Ntui; [4°31'N, 11°30'E]; 18 Nov. 1969; fr.; R. Letouzey 9568bis, BR [BR0000015776747], P [P04707227], YA [YA0029462] • Binoum ; 4°12'N, 11°02'E; 18 Oct. 2022; fl. ♂; B. Sonké 7097; BR, BRLU, M, MA [ MA 959273 ], MO, P, YA • Binoum; 4°12'N, 11°02'E; 18 Oct. 2022; fl. ♀; B. Sonké 7096; BR, BRLU, M, MA [ MA 959272 ], MO, P, YA • Binoum; 4°12'N, 11°01'E; 18 Oct. 2022; fl. ♀; B. Sonké 7095; BR, BRLU, M, MA [ MA 959277 ], MO, P, YA • Binoum; 4°12'N, 11°02'E; 18 Oct. 2022; fr.; B. Sonké 7094; BR, BRLU, E, MA [ MA 959271 ], P n.v., YA • Binoum; 4°12'N, 11°02'E; 13 Oct. 2022; fr.; B. Sonké & M. Libalah 7074; BR, BRLU, MA [ MA 959276 ], MO, P, YA • Binoum; 4°12'N, 11°02'E; 13 Oct. 2022; fr.; B. Sonké & M. Libalah 7072; BR, BRLU, MA [ MA 959275 ], MO, P, YA • Binoum; 4°12'N, 11°02'E; 13 Oct. 2022; fr.; B. Sonké & M. Libalah 7071; BR, BRLU, M, MA [ MA 959274 ], MO, P, YA • Binoum; 4°12'N, 11°02'E; 22 Dec. 2022, fr.; B. Sonké & M. Simo 7126; BR, BRLU, E, K, MA [ MA 959270 ], MO, P, YA • Binoum, sur une coline; 4°12'N, 11°02'E; 15 Oct. 2022; fl. ♂; F. Nzoyeuem & al. 149; BRLU, YA • Kikot, en Aval du pont sur la Sanaga; 4°09'N, 11°00'E; 10 Nov. 2022; fl. ♀; TRCam plot 618 (F. Nzoyeuem & al.); BRLU, YA. - West • Près Mankare, 45 km SE Foumban; [5°24'N, 11°10'E]; 23 Oct. 1974; fl. ♀, fr.; R. Letouzey 12989; BRLU [BRLU0000164], MO [MO-5594595], P [P04707473], YA [YA0029404] .

NIGERIA - Adamawa • Gangumi , on the second mile line from the base line; [7°56'N, 11°11'E]; 11 Dec. 1954; fr.; FHI 28890 (M.G. Latilo & B.O. Daramola); FHO [FHO 00018584], K [2 sheets] .

Figures

Figure 2. Distribution of Drypetes verrucosa (green circles) and D. stevartii (red circles).

Figure 3. Drypetes stevartii Sonke & Quintanar. A. Branchlet and leaves. B. Female inflorescence. C. Male inflorescence. D. Infructescences on the trunk. E. Infructescence with ripe fruits. F. Infructescence with immature fruits. A, C from Sonke 7097; B from Sonke 7096; D from Sonke 7127 (type); E from Sonke 6975; F from Sonke 7094. Photographs A-F by Bonaventure Sonke, E by Murielle Simo-Droissart.

Figure 4. Wild Apis mellifera visiting a male flower of Drypetes stevartii.