Drypetes verrucosa Pierre ex Hutch. (Hutchinson 1912: 677)

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 verrucosa Pierre ex Hutch. (Hutchinson 1912: 677)

Figs 1 , 2

Type.

GABON • [Estuaire] Environs de Libreville, Sibang , [0°25'N, 9°30'E]; 23 Oct. 1902; fl. ♀, fr.; T.J. Klaine 2382; lectotype (designated here): P [P04777265]; isolectotypes: BM, BR [BR0000006238162, BR0000006238490, BR0000006238827, BR0000006239152], K [K000406384, K000406385], P [P04777262, P04777263, P04777264, P04777266]; syntypes : GABON • [Estuaire] Environs de Libreville; 19 Feb. 1902; fl. ♀, fr.; T.J. Klaine 2482; BM, K, P [P04777258, P04777259, P04777260, P04777261] • Environs de Libreville ; 26 Dec. 1901; fl. ♀, fr.; T.J. Klaine 2589; P [P04777257, P04777267] ).

Description.

Tree up to 25 m tall, with plagiotropic branches; trunk up to 16 cm in diameter, fluted or slightly fluted at the base; bark greenish-brown, smooth, rough and flaky when old; young branchlets subterete, slightly sulcate, shortly pubescent, trichomes 0.1-0.3(-0.6) mm; terminal buds scaly, scales 2.5-2.6 × 0.7-1 mm, ovate, firm, slightly keeled, shortly pubescent outside with trichomes 0.1-0.3 mm, glabrous inside, ciliate, cilia 0.1-0.3 mm. Leaves: stipules (3.7-)5.9-8(-12.5) × 0.2-0.5 mm, linear, laciniate, often with a single lacinia of 1.5-4.1 mm near the base, sometimes with 1-2 pairs of lateral laciniae, shortly pubescent outside, glabrous inside, ciliate, trichomes 0.2-0.5 mm, cilia 0.2-0.4 mm, subpersistent; petiole (4.5-)5.2-6.7(-9) mm long, (1.4-)1.7-2 mm in diameter, smooth or hardly wrinkled when dried, densely and shortly pubescent, glabrescent when old, trichomes 0.1-0.2(-0.3) mm; blade (9.3-)11-16.6(-17.7) × (3.4-) 5.4-7.6(-8.8) cm, elliptic to broadly elliptic, papery to subcoriaceous, glossy and dark-medium green above, dull pale green beneath, base slightly obtuse to obtuse, markedly asymmetrical, rounded on one side, less often oblique, basal sides meeting the petiole up to 0.4 mm apart along the petiole length, margin crenulate-serrulate for most of its length, teeth to 1.3(-2.4) mm, acute, frequently blunt, flat to slightly recurved near the blade base, shortly acuminate, apex 10-20 mm, abaxial surface between the nerves sparingly pubescent, trichomes 0.1-0.4 mm; midrib smooth, slightly longitudinally wrinkled when dry, shortly and densely pubescent, trichomes 0.1-0.5 mm; first order lateral veins 6-8 pairs, ascending, more or less regularly spaced, slightly depressed above, prominent beneath, curved and anastomosing well within the margin, oriented at (49-)63-74(-79)° to the midrib, minutely pubescent, trichomes 0.1-0.2 mm; second order venation loosely reticulate, hardly or not raised above, slightly so beneath. Male inflorescence borne on more or less horizontal cushion-like excrescences of the trunk (category I), in many-flowered clusters, often in groups of 30 or more flowers; bracts 0.6-0.9 × 0.7-0.8 mm, ovate to suborbicular, minutely pubescent outside, glabrous inside, minutely ciliate, trichomes and cilia 0.1-0.2 mm, barely distinguishable with a × 10 handlens. Male flowers long pedicellate, pinkish; pedicel 22-35(-40) mm long, 0.3-0.7 mm in diameter, slender, very sparingly and shortly pubescent, trichomes 0.1-0.2 mm; sepals (4-)5, 4.9-5.3 × 4.1-5.5 mm, widely ovate to suborbicular, cucullate, imbricate, the inner often smaller than the outer, glabrous outside and inside, margin margin minutely ciliate for most of its length, cilia 0.1-0.2 mm; stamens 14-16, one-whorled, surrounding the disc, more or less enveloped by its marginal lobes, filaments 4.4-4.5(-9.8) mm, white, anthers 1.2-1.5(-2) mm long, 0.9-1(-1.3) mm in diameter, ellipsoid, cream-coloured, subbasifixed to dorsifixed, introrse, pale yellow, glabrous; disc (0.3-) 0.8-0.9 mm high, (2.7-)4.3-4.7 mm in diameter, convex, thick, very rugose, cream-coloured, densely and shortly pubescent, trichomes 0.1-0.3 mm, pistillode absent. Female inflorescence borne on cushion-like excrescences of the trunk (category I), in clusters of 10-35 flowers; bracts (0.6-)0.9-1.1 × 0.7-0.9 mm, otherwise similar to the male ones. Female flowers pedicellate; pedicel (6.3-)7.9-13.2(-20) mm long, 0.9-1.4 mm in diameter, robust, sparsely and minutely pubescent, glabrescent, trichomes 0.1-0.2 mm; sepals 5, 5-5.7 × (4-)6-6.3 mm, otherwise similar to the male ones; disc 0.9-1 mm high, (2.5-)4.2-4.4 mm in diameter, concave, cupulate, fleshy, shortly pubescent, more densely towards the margin, trichomes 0.2-0.3 mm; style 1, to 0.5 mm, unbranched; stigmas 3, obdeltoid, stigmatic surface 1.9-2.5 mm long, 1.3-3(-3.4) mm wide; ovary 2.4-3.4 mm long, 4.1-4.7 mm in diameter, subglobose, 3(-4)-celled, densely and shortly pubescent, trichomes 0.2-0.5 mm. Fruits (27-) 29.5-34(-38.1) mm long, (15-)23-29 mm in diameter, ellipsoid, sepals, style, and stigmas caducous, exocarp uneven, yellowish brown turning yellowish orange when ripe, shortly pubescent, trichomes 0.1-0.3 mm, mesocarp 2-5 mm thick when dried, hard, endocarp 1-2 mm thick, bony, 1-3-seeded; seeds 17.1-21 mm long, 8-9 mm in diameter; fruiting pedicel 21-33 mm long, 1.2-2.7 mm in diameter, sparsely and shortly pubescent, trichomes 0.1-0.3 mm.

Distribution and chorology.

Endemic to Gabon, mostly distributed in the northwest: Estuaire, Moyen-Ogooué, Ngounié, and Woleu-Ntem (Fig. 2 ). Lower Guinea subcentre of endemism ( White 1979).

Habitat.

Primary or secondary evergreen forests, sandy or calcareous soils, sometimes on periodically flooded soils; at 40-205 m a.s.l.

Phenology.

Flowering specimens were collected from June to February, and fruiting specimens from October to April.

Nomenclature.

Hutchinson described D. verrucosa on the basis of three gatherings made by Théophile J. Klaine in the surroundings of Libreville in 1901 and 1902 ("Lower Guinea. Gaboon: in the neighbourhood of Libreville, Klaine 2382 2482! 2589!", see Hutchinson 1912), as well as on an unnumbered illustration with analysis drawn by E. Delpy in 1902 (February), based on Klaine 2589, kept in the herbarium of the National Museum of Natural History in Paris and previously reproduced in Harris et al. (2021). We have chosen the specimen P04777265 of the gathering Klaine 2382 as lectotype, since we consider it to be the most suitable specimen located among the syntypes cited in the protologue. The illustration belongs to the Tabulae herbarii L. Pierre ( Delpy 18??-19??) opera utique rej., a suppressed work ( Rijckevorsel 2011; Turland et al. 2018). Consequently the designation " Cyclostemon verrucosus " is not effectively published in those printed and distributed drawings, and not validly published in the protologue of D. verrucosa as it is listed as a synonym. Therefore, we have not listed it above.

Etymology.

The specific epithet comes from the Latin adjective verrucosus, which means warty, rough, or rugged. Hutchinson (1912) did not specify the reason for the epithet of this species name in the protologue, though it seems reasonable to assume that he referred to the rough, uneven surface of the fruit.

Preliminary IUCN conservation assessment.

Drypetes verrucosa is known from 20 gatherings made from the beginning of the XXth century to 2021. However, we have excluded from our analysis three historical gatherings made in the area of Libreville (Klaine 2382, 2482, and 2589) and the region between Ogooué and Cameroon (Le Testu s.n.) because their localities are too imprecise. The 16 remaining gatherings represent 14 ocurrences and 9-11 subpopulations. The extent of occurrence (EOO) is estimated to be 25,131 km2, which falls within the limits for Near Threatened under subcriterion B1, whereas the area of occupancy (AOO) is estimated to be 56 km2, which falls within the limits for Endangered under subcriterion B2. Two occurrences are located within protected areas: one within Pongara National Park and another within Akanda National Park. Six occurrences are located within six different forestry concessions and are threatened by logging activities. The two occurrences at Mabounié are threatened by ongoing mining exploration activities. One occurrence at the Ndombo oil concession area is threatened by sand extraction. The other three occurrences from Lambarene ( Moyen-Ogooué), Mondah-Liby (Estuaire), and Lalara (Woleu-Ntem) are threatened by (local) wood harvesting. These activities indicate a decline in the extent and habitat quality of the species. As a consequence, the 14 occurrences represent 13 locations (sensu IUCN Standards and Petitions Committee 2022), with regard to the most serious plausible threats (sand extraction and mining exploration activities), being more than the upper limit for Vulnerable under subcriterion B2. We consider that habitat loss will continue in the near future, which could lead to the disappearance of at least two occurrences, representing two locations. These future disappearances will thus lead to a continuing decline in AOO, number of locations, and mature individuals. Drypetes verrucosa is therefore assessed as Near Threatened (NT).

Additional material examined.

GABON - Estuaire • Concession Sud Estuaire, rivière Remboué; 0°07'S, 9°52'E; 19 Jun. 2021; fl. ♂; J. Klein & al. 564; BR n.v., BRLU, P n.v. • Mondah-Liby; [0°46'N, 9°38'E]; 30 Sep. 1952; veg.; F. Bernard 889; LBV [LBV0030789] image, NHN [NHN4557230] n.v. • National Park Akanda, Ngounzi débarcadère; 0°34'N, 9°41'E; 11 Dec. 2012; fr.; E.L.A.N. Simons & al. 1001; BR n.v., LBV n.v., MO [MO-6561895] • Ndombo oil-concession area of CONOCO, ca 4 km SW of No Ayong; 0°37'N, 9°39'E; 22 Feb. 1991; fr.; J.M. Reitsma 3683; LBV [LBV0030851] image • Remboué; [0°02'N, 9°50'E]; 30 Jul. 1951; veg.; Sabire & S. Etasse 340; LBV image. - Moyen-Ogooué • Au Nord-est du lac Azingo; 0°19'S, 10°03'E; 4 Jun. 2014; veg.; A. Boupoya & al. 944; BR [BR0000016171442], BRLU n.v. • Au sud de Lambaréné, entre 5 et 10 km depuis la ville, entre l’Ogooué et la route de Fougamou; 0°55'S, 10°21'E; 15 Apr. 2015; fr.; E. Bidault & al. 1940; BR [BR0000016172166], BRLU [BRLU0002958] n.v., P [P00854948] • Lambaréné, along the Ogooué stream; 0°53'S, 10°09'E; 15 Oct. 2012; fl. ♂; B. Sonké & al. 6041; BR [BR0000024385589], BRLU, MO [MO-6729952] • Route menant au lac Azingo, à 35 km au nord-ouest de Lambarené; 0°27'S, 10°05'E; 26 Oct. 2014; fl. ♂; E. Bidault & al. 1861; MO [MO-6681694] • Zone de Mabounié, à 45 km au sud-ouest de Lambaréné, rive nord de la rivière Ngounié; 0°45'S, 10°36'E; 4 Feb. 2013; fr.; E. Bidault & al. 1054; BRLU [BRLU0000151], LBV image, MO [MO-6729953], NHN [NHN1380674] n.v., P [P00854579] • Zone de Mabounié, à environ 45 km au sud-est de Lambaréné, rive ouest de la Ngounié, plot Mabou 009; 0°49'S, 10°29'E; 14 Oct. 2012; veg.; IRD plot 332 (N. Barbier & al.); BRLU • Zone de Mabounié, à environ 45 km au sud-est de Lambaréné, rive ouest de la Ngounié, plot Mabou 009; 0°49'S, 10°29'E; 14 Oct. 2012; veg.; IRD plot 331 (N. Barbier & al.); BRLU. - Ngounié • Forêt au Nord de Lambarénékili, à environ 5 km au nord de la rivière Niambo-Kamba; [1°26'S, 10°17'E]; 15 Aug. 2008; veg.; G. Dauby & al. 1375; BRLU • Sindara; 1°02'S, 10°39'E; 16 Jul. 1979; fl. ♂; G.M.P.C. Le Testu 2291; B [B 10 0366532], BM, BR [BR0000015019523, BR0000015019547], K, LISC, P [P04777254, P04777255, P04777256]. - Woleu-Ntem • [La] Lara; [0°21'N, 11°28'E]; 27 Oct. 1933; fl. ♂; G.M.P.C. Le Testu 9349; K, BM, BR [BR0000015019554], MO [MO-5594599], P [P04707826], WAG [WAG.1564868] • [La] Lara; [0°21'N, 11°28'E]; 27 Oct. 1933; fl. ♀; G.M.P.C. Le Testu 9347; K, BM, BR [BR0000015777539], P [P04707828, P04707829, P04707831], WAG [WAG.1564872, WAG.1564873] • Région entre Ogooué et Cameroon; 19 May 1936; veg.; G.M.P.C. Le Testu s.n.; P [P04707827, P04707830].

Figures

Figure 1. Drypetes verrucosa Pierre ex Hutch. A. Stipule and petiole. B. Branchlet and leaves. C. Male inflorescences on the trunk. D. Male flower. E. Fruits, detail. F. Infructescences with ripe fruits on the trunk. A, F from Bidault 1940; B, D from Bidault 1861; C from Sonke 6041; E from Bidault 1054. Photographs taken by the collectors.

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