Drypetes cauta D.J.Harris, Barberá & Quintanar, 2023

Quintanar, Alejandro, Harris, David J., Nguema, Diosdado & Barberá, Patricia, 2023, Notes on cauliflory, sexual dimorphism and biogeography in Drypetes (Putranjivaceae, Malpighiales) and a taxonomic treatment for D. gabonensis and two new cauliflorous threatened species from Central Africa, D. aphanes sp. nov. and D. cauta sp. nov., European Journal of Taxonomy 888, pp. 175-202 : 190-193

Drypetes cauta D.J.Harris, Barberá & Quintanar sp. nov.

urn:lsid:ipni.org:names:77319369-1

Fig. 3h – n

Type

GABON • Ngounié – Boudyanguila, Pays itsogles; [1º56′S 11º30′E]; 21 Sep. 1925; G.M.P.C. Le Testu 5512; fl. ♀; holotype: P [ P04707049 ]; isotypes: BM, BR [ BR0000015777379 ], P [ P04707045 , P04707048 ].

Diagnosis

Haec species a Drypete gabonensi ramulis junioribus omnino glabris, cortice ramulorum tessellato, petiolis (3.4‒)5.8‒7(‒7.5) mm longis, confertim rugosis, in sicco saepe fuscatis, foliis ad basim plerumque obliquis, inflorescentiis in truncum positis, sepalis masculinis 5, 4.2‒5.3 × 4.1‒4.7 mm, late ovatis, ac abaxialiter glabratis, disco convexo, in diam. 3.1‒3.3 mm, staminibus 16 vel 17, stylis eramosis 0.4‒0.6 mm longis, atque stigmatibus obdeltoideis differt.

Etymology

The specific epithet of this new species is the nominative feminine singular of the Latin adjective ‘ cautus ’, which means ‘cautious, careful, prudent, etc.’ The cautious character of D. cauta sp. nov. seems to be apparent after having spent a long time hidden in herbaria, after the first gatherings made by Le Testu during the first half of the past century, until its description today.

Material examined

GABON – Estuaire • Concession Sud Estuaire, rivière Remboué ; 0º7′S 9º 51′E; 26 Jun. 2021; MBG transect 7194 (J. Klein, E. Akouangou, J.D. Kaparidi, L.C. Moungoudy & C.D. Kombil; veg.; BRLU – Ngounié • G.M.P.C. Le Testu 5512 (type, see above) – Ogooué-Ivindo • SE of Booúe , in Lutexfo timber concession; 0º21′S 12º14′E; 23 Nov. 1993; G.D. McPherson 16249; fr.; K, LBV [ LBV0008206 ], MO [ MO 4647294 ], PRE, WAG [ WAG.1563832 ] – Ogooué-Lolo • Région de Lastoursville, Iméno ; [1º30′S 12º19′E]; 10 Sep. 1930; G.M.P.C. Le Testu 8327; fl. ♂; BM, BR [ BR0000015777188 ], P [ P04707811 , P04707812 ], WAG n.v. – Woleu-Ntem • Concession Rougier du Haut-Abanga, Sud-Est de Mikongo , partie Nord des montagnes Mekié ; [0º25′N 11º13′E]; 17 Jul. 2008; G. Dauby 1022, D. Nguema, E. Mounoumoulossi & P. Bissiemou; fr.; BRLU, MO [ MO 6358905 ].

REPUBLIC OF THE CONGO – Kouilou • Mayombe hills, near Niari River ; 4º2′S 12º9′E; 18 Oct. 2010; R. M’Boungou 462, X. M. van der Burgt & F. Gislain; fl. ♀; IEC [ IEC025751 ], K [ K000683528 ].

Description

Treelet to 8 m high, dioecious; trunk to ca 15 cm in diameter, bark finely tessellated, somewhat flaky, dark-coloured; branchlets terete or slightly flattened, sulcate, glabrous; apical buds scaly, scales 1.3‒1.7 × 2.1‒2.7 mm, ovate-suborbicular, strongly cucullate, glabrous, minutely ciliate, cilia to 0.1 mm. Leaves simple, alternate, lustreless above and beneath; stipules 1.4‒1.6 × 0.2‒0.4 mm, narrowly triangular, deciduous, very soon falling, glabrous, ciliate at the margin, trichomes to 0.2 mm; petiole (3.4‒)5.8‒7(‒7.5) mm long, 1.4‒2 mm in diameter, finely and densely wrinkled, channeled above, drying dark-coloured or blackish, glabrous; leaf blade (10.5‒)12.6‒15.6(‒19.2) × (2.4‒)3.8‒5.2(‒6.2) cm, narrowly elliptic, subcoriaceous, acuminate, apex (4‒)8.1‒11.2(‒17) mm, base acute to slightly obtuse, oblique, margin obscurely and shallowly crenulate-serrulate, crenulae to 0.2 mm, flat to slightly recurved near the blade base, underside of the lamina glabrous; midrib longitudinally wrinkled, glabrous, first order lateral veins (6‒)8(‒10) pairs, ascending, somewhat irregularly spaced, depressed above, prominent beneath, obscurely diminishing and anastomosing near the margin, forming angles of 45‒60º to the midrib, glabrous, second order venation hardly raised above and very slightly beneath. Male inflorescence trunciflorous (category I), many-flowered clusters; bracts 1.2‒1.5 × 1.3‒1.6 mm, ovate to obovate, quite irregular, glabrous, minutely ciliate at margin, cilia to 0.2 mm. Male flowers plate-like at anthesis, yellow, pedicel 3.6‒7.7 mm long, 0.3‒0.8 mm in diameter, more or less robust, glabrous; sepals 5, 4.2‒5.3 × 4.1‒4.7 mm, widely ovate, obtuse, imbricate, cucullate, glabrous outside and inside, minutely ciliate at margin, cilia to 0.1 mm; stamens 16‒17, obscurely whorled, mainly surrounding the disk and enveloped by its marginal folds, some of them (2 or 3) penetrating, filaments 2.2‒2.3 mm long, anthers 1.4‒1.5 mm long, 0.6‒0.7 mm in diameter, ovate-elliptic, dorsifixed, introrse, glabrous; disk 3.1‒3.3 mm in diameter, ca 0.4 mm high, convex, strongly plicate, convolute, glabrous. Female inflorescence trunciflorous (category I) from the base up or nearly so to ca 4 m height, many-flowered clusters; bracts 1‒1.9 × 1.3‒1.6 mm, as the male ones. Female flowers plate-like at anthesis, with pedicel 7.5‒10.9 mm long, 0.7‒0.9 mm in diameter, more or less robust, glabrous; sepals (4‒)5, 4.1‒4.7 × 4.2‒4.8 mm, widely ovate, imbricate, cucullate, glabrous outside and inside, minutely ciliate at margin, cilia to 0.1 mm; disk 4.1‒4.3 mm in diameter, 0.3‒0.8 mm high, cupulate, fleshy, glabrous; style 1, 0.4‒0.6 mm long, hollow, unbranched; stigmas 3, each arm 0.8‒1.1 mm long, stigmatic surface 1.5‒2.3 mm wide, obdeltoid; ovary 2.5‒2.8 mm long, 4.1‒ 3.9 mm in diameter, globose, longitudinally flattened, apex depressed, 3-celled, glabrous. Fruit 15‒16.8 mm long, 12.1‒15.4 mm in diameter, widely elliptic, apex depressed, surface smooth, even, green, glabrous, without sepals, stigmas subpersistent, 3-celled, 2(‒3)-seeded, seeds ca 9 mm long, ca 2.2 mm in diameter; fruiting pedicel 11.3‒12.2 mm long, 0.8‒1.1 mm in diameter, glabrous.

Distribution and habitat

Central Africa. Gabon (Estuaire, Ngounié, Ogooué-Ivindo, Ogooué-Lolo and Woleu-Ntem) and Republic of the Congo (Kouilou) ( Fig. 4 ). Primary evergreen forests; 400‒650 m a.s.l.

Phenology

Flowering specimens were collected from September to October, fruiting specimens from July to November.

Notes

This new treelet to 8 m high from the rainforests of Gabon and Republic of the Congo also shows the inflorescences placed on the trunk, like D. aphanes sp. nov. As for D. aphanes , the overall morphological characteristics of D. cauta sp. nov. let us classify it in D. sect. Sphragidia , due to its deciduous stipules, high number of stamens, 3-locular smooth ovaries and subsessile stigmas.

Drypetes cauta sp. nov. differs from the species treated above by a series of vegetative and reproductive characters (see above the notes under D. gabonensis and D. aphanes sp. nov., as well as Table 1 for a summary of diagnostic characters). The petiole of D. cauta is often shorter than that of D. aphanes ((3.4‒)5.8‒7(‒7.5) vs (5.3‒)7‒8.1(‒8.6) mm) and the courses of the first order lateral veins form lower angles to the midrib (45‒60º vs (54‒)58‒81º). The number of stamens is lower in D. cauta (16‒17 vs (11)14‒15) and they are obscurely whorled, some of them (2‒3) penetrating within a very plicate and convolute disk of complex structure, while in D. aphanes the stamens do not penetrate a rugose disk. Drypetes cauta additionally has longer female pedicels (7.5‒10.9 vs 2.9‒3.2 mm), which are much thinner in the fruit than those of D. aphanes (0.8‒1.1 vs 1.3‒2.3(‒2.9) mm); it also bears longer styles (0.4‒0.6 vs to 0.1 mm) that remain, along with the stigmas, for a long period of time on the fruit than those of D. aphanes . As we have mentioned, the fruit of D. cauta is different and not to be confused with that of the previous species, smaller (15‒16.8 × 12.1‒15.4 vs (18.2‒)18.8‒22.6 × (15.7‒)18‒23.1(‒23.4) mm) and widely elliptic with a quite even surface, while the fruit of D. aphanes is subglobse and its surface is uneven.

IUCN Red List preliminary status

The extent of occurrence (EOO) of D. cauta sp. nov. is estimated to be 66 594 km 2, exceeding the upper threshold for ‘Vulnerable’ status under subcriterion B1, whereas its area of occupancy (AOO) is estimated to be 24 km 2, which falls within the limits for ‘Endangered’ status under the subcriterion B2. The species is known from six gatherings, representing six occurrences, all made between 1925 and 2021, and six subpopulations. Considering the forest cover, which is still significant in these countries, we do not regard any of these occurrences as extirpated. All of the occurrences are located outside of protected areas. The five occurrences in the different provinces of Gabon and the one in the Republic of the Congo are located within six different forest concessions, and are, therefore, threatened by logging. This activity presumably induces a decline in the extent and quality of the habitat of this species. As a consequence, these six occurrences represent six locations (cf. IUCN Standards and Petitions Committee 2022) with regard to the most serious plausible threat (logging). Drypetes cauta is therefore assigned a preliminary status of ‘Vulnerable’ [VU B2ab(iii)].

Figures

Fig. 3. Drypetes aphanes Quintanar, D.J. Harris & Barberá sp. nov. a. Branch and leaves. b. Petiole and leaf base, adaxial view. c. Female inflorescence. d. Female flower. e. Female sepal, abaxial view. f. Male flower. g. Fruit. – h–n. D.cauta D.J.Harris, Barberá & Quintanar sp. nov. h. Branch and leaves. i. Petiole and leaf base, adaxial view. j. Terminal bud and stipules. k. Female flower. l. Female sepal, abaxial view. m. Male flower. n. Fruit [a–c, g. Breteler 14796 (MO 6561411). d–e. McPherson 16666 (MO 6343500). f. McPherson 16690 (MO 6343501). h–i, m. Le Testu 5512 (P04707049). j. M’Boungou462 (K). k–l. Le Testu 8327 (P04707812). n. McPherson 16249 (MO 04647294)]. Illustration by Román García Mora.

Fig. 4. Distribution of Drypetes gabonensis Pierre ex Hutch. (blue circles), Drypetes aphanes Quintanar, D.J.Harris & Barberá sp. nov. (red triangles) and D.cauta D.J.Harris, Barberá & Quintanar sp. nov. (green squares).