Drypetes aphanes Quintanar, D.J.Harris & Barberá, 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 : 187-189

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

urn:lsid:ipni.org:names:77319368-1

Fig. 3a – g

Type

GABON • Estuaire – ± 26 km before Mbé River on Kango road; 0º21′N 9º58′E; 22 Oct. 2000; F.J. Breteler 15662; fr.; holotype: MO [ MO 6683078 ]; isotypes: WAG [ WAG.1564809 ], LBV [ LBV0002377 ] .

Diagnosis

Haec species a Drypete gabonensi ramulis junioribus omnino glabris, cortice ramulorum tessellato, petiolis (5.3‒)7‒8.1(‒8.6) mm longis, confertim rugosis, in sicco saepe pallidis, foliis ad basim plerumque obliquis, inflorescentiis in corticem veterem truncumque positis, sepalis masculinis 5, (3.9‒)4.4‒5.2(‒5.6) × (4.3‒)4.6‒5.2(‒6.5) mm, late ovatis, ac abaxialiter glabratis, disco convexo, in diam. 3.4‒4.6 mm, staminibus (11 ad)14 vel 15, stylis eramosis, ca 0.1 mm longis, atque stigmatibus obdeltoideis differt.

Etymology

The specific epithet of this new species is the Neolatin adjective ‘ aphanes ’ (from Gr. ἀφᾰνής), which means unseen, invisible, unnoticed, not manifest, unknown, etc. Because of the low number of gatherings of D. aphanes sp. nov. made to date and the recent collection dates of all of them.

Material examined

GABON – Estuaire • F.J. Breteler 15662 (type, see above) • ca 3 km on Kougouleu-Médouneu road; 0º25′ N, 9º55′ E; 14 Oct. 1997; F.J. Breteler 14274, M.E. Leal, J.M. Moussavou & G. Nang; fl. ♂; BR [ BR0000015777454 ], BRLU, LBV [ LBV0030849 ], MO [ MO 6561417 ], WAG [ WAG.1564805 ] – Ogooué-Lolo • ca 30 km E of Lastoursville ; 0º40′ S, 13º0′ E; 18 Nov. 1991; F.J. Breteler 10545 & C.C.H. Jongkind; fr.; LBV, WAG [ WAG.1564829 ] • East of Lastoursville , near Bambidie, C.E.B. chantier; 0º45′S 13º3′E; 25 Sep. 1996; G.D. McPherson 16690; fl. ♂; LBV [ LBV0008192 ], MO [ MO 6343501 ], WAG n.v . • ibid.; 0º46′S 13º3′E; 23 Sep. 1996; G.D. McPherson 16666; fl. ♀; LBV [ LBV0008194 ], MO [ MO 6343499 , MO 6343500 ], WAG n.v . • Makande surroundings, c. 65 km SSW of Booué; 0º41′S 11º55′E; 26 Jan. 1999; F.J. Breteler 14796, G. Caballé, Y.A. Issembé, J.J. Moussavou & O. Pascal; fr.; BR [ BR0000015777386 ], FHO n.v., HUJ n.v., K, LBV [ LBV0030870 ], MO [ MO 6561411 ], NY n.v., P n.v., PE n.v., WAG [ WAG.1564806 , WAG.1564807 , WAG.1564808 ], YA n.v .

Description

Tree to 15 m high, dioecious; trunk to 20 cm in diameter, slightly fluted at the base, bark very finely tessellated, light-coloured; branchlets terete to slightly sulcate, glabrous; apical buds scaly, scales 1.2‒1.4 × 1‒1.6 mm, widely ovate, glabrous. Leaves simple, alternate, lustreless and dark-medium green above, much paler beneath; stipules not seen, deciduous, very soon falling; petiole (5.3‒)7‒8.1(‒8.6) mm long, (1.1‒)1.7‒2.1(‒2.3) mm in diameter, finely and densely wrinkled, channelled above, drying light-coloured, glabrous; leaf blade (12.5‒)14.3‒16.4(‒18.8) × (4.2‒)5.1‒6.1(‒7.4) cm, widely to narrowly elliptic, subcoriaceous or stiffly chartaceous, acuminate, apex (6‒)8‒15(‒18) 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 7‒9, ascending, regularly spaced, slightly depressed above, slightly prominent beneath, noticeably curved and anastomosing well within the margin, forming angles of (54‒)58‒81º to the midrib, glabrous, second order venation hardly raised above and very slightly beneath. Male inflorescence trunciflorous (category I), many-flowered clusters; bracts 0.7‒0.9 × 0.8‒1 mm, ovate to obovate, quite irregular in shape, glabrous, minutely ciliate at margin, cilia to 0.1 mm. Male flowers plate-like at anthesis, white, pedicel 3.8‒4.3(‒5.2) mm long, (0.6‒)0.9‒1.2(‒1.4) mm in diameter, robust, glabrous; sepals 5, (3.9‒)4.4‒5.2(‒5.6) × (4.3‒)4.6‒5.2(‒6.5) mm, widely ovate to slightly obovate, imbricate, slightly cucullate, obtuse, glabrous outside and inside, sometimes minutely ciliate, cilia to 0.1 mm; stamens (11‒)14‒15, apparently one-whorled, surrounding the disk, more or less enveloped by its marginal folds, filaments (3.4‒)4‒6(‒6.3) mm long, anthers 1.6‒1.9 mm long, 0.7‒1.1 mm in diameter, ovate-elliptic, dorsifixed, introrse, yellow, glabrous; disk 3.4‒4.6 mm in diameter, 0.3‒0.5 mm high, convex, very rugose, glabrous. Female inflorescence trunciflorous (category I) from the base up or nearly so to ca 10 m height, occasionally on old wood of branches (category II), many-flowered clusters; bracts 0.9‒1.5 × 0.7‒1.2 mm, as the male ones. Female flowers plate-like at anthesis, white; pedicel 2.9‒3.2 mm long, 1‒1.1 mm in diameter, robust, glabrous; sepals 5, 3.4‒4.1 × 3.9‒4 mm, widely ovate to slightly obovate, imbricate, slightly cucullate, glabrous outside and inside, without cilia; disk 3‒3.2 mm in diameter, 1.1‒1.3 mm high, cupulate, fleshy, glabrous; style 1, to 0.1 mm, hollow, unbranched; stigmas 3, each arm 0.6‒0.8 mm long, stigmatic surface 1‒1.3 mm wide, obdeltoid; ovary 1.4‒1.5 mm long, 2.2‒2.4 mm in diameter, subglobose, apex slightly depressed, 3-celled, glabrous. Fruits (18.2‒) 18.8‒22.6 mm long, (15.7‒)18‒23.1(‒23.4) mm in diameter, subglobose, apex slightly depressed, surface smooth, uneven, green, glabrous, without persistent sepals or stigmas, 3-celled, (2‒)3-seeded, seeds (11.5‒)12.1‒16.1(‒16.4) mm long, (4.8‒)5.9‒6.4(‒6.7) mm in diameter; fruiting pedicel (6.7‒)9‒12.6(‒13) mm long, 1.3‒2.3(‒2.9) mm in diameter, glabrous.

Distribution and habitat

Central Africa. Endemic to Gabon (Estuaire and Ogooué-Lolo) ( Fig. 4 ). Primary and secondary evergreen forests; 30‒660 m a.s.l.

Phenology

Flowering specimens were collected from September to October, fruiting specimens from October to January.

Notes

The inflorescences of this new species of medium-sized tree, according to the information supplied by herbarium labels, belong to category I, although in Breteler 14796 we have found a fruit on the old wood of a branch, which may imply the existence of inflorescences of category II. As for D. gabonensis , only future field observations can help to assess the frequency with which inflorescences can be found on the main branches of D. aphanes sp. nov. The overall morphology of D. aphanes let us classify it in D. sect. Sphragidia , i.e., deciduous stipules, high number of stamens, 3-celled smooth ovaries and subsessile stigmas.

The fruits, subglobose with slightly depressed apex and uneven surface, recall those of D. gabonensis , a species from which, as we have commented above, it differs by a series of vegetative and reproductive characters (see above the notes under D. gabonensis , as well as Table 1 for a summary of diagnostic characters). No colour except green has been recorded for these fruits and fruit colour may have diagnostic value ( D. gabonensis bears red ripe fruits), it will be necessary to wait for new gatherings of this species to find out if they remain green in a mature state. Drypetes aphanes sp. nov. also differs from D. gabonensis by the leaf nervation, because the courses of the first order lateral veins are strongly arched and loop clearly well within the margin, while those of this later species and D. cauta sp. nov. are not so strongly arched and loop obscurely near the margin; as well, the petiole of D. aphanes often dries light-coloured in herbarium specimens, while those of the others dry dark-coloured or even blackish.

Both D. aphanes sp. nov. and D. cauta sp. nov. present inflorescences mostly from category I. However, the petiole of D. aphanes is often longer than that of D. cauta ((5.3‒)7‒8.1(‒8.6) vs (3.4‒)5.8‒7(‒7.5) mm) and the courses of the first order lateral veins run at greater angles to the midrib ((54‒)58‒81º vs 45‒60º). Neither of these species shows the high degree of morphologic dimorphism of D. gabonensis regarding their flowers and the flowers of different sexes in these two species have corresponding dimensions and characteristics. In both species the flowers are shortly stalked, glabrous, sometimes with minute marginal cilia, and plate-like when fully open during anthesis. The number of stamens is lower in D. aphanes ((11)14‒15 vs 16‒17) and their arrangement also differs: while those of this species surround the disk and are more or less enveloped by the disk marginal lobes, in D. cauta they show a similar disposition, but are quite obscurely whorled and some of them penetrate within a different, very plicate and convolute disk, while the male disk of D. aphanes is just rugose. Female flowers and fruits of these species also offer diagnostic characters, such as shorter pedicels (2.9‒3.2 × 1‒1.1 vs 7.5‒10.9 × 0.7‒0.9 mm, flower) which are much thicker in the fruit of D. aphanes (1.3‒2.3(‒2.9) vs 0.8‒1.1 mm wide), and shorter styles (to 0.1 vs 0.4‒0.6 mm), which are quite persistent in D. cauta sp. nov. and not observed in any fruit of D. aphanes . Finally, the fruit body of D. aphanes sp. nov., as well as that of D. gabonensis , is bigger than the fruit of D. cauta ((18.2‒)18.8‒22.6 × (15.7‒)18‒23.1(‒23.4) vs 15‒16.8 × 12.1‒15.4 mm) and also differs by its shape (subglobse vs widely elliptic) and surface (uneven vs even).

IUCN Red List preliminary status

The extent of occurrence (EOO) of D. aphanes sp. nov. is estimated to be 8 756 km 2, which falls within the limits for ‘Vulnerable’ status under the 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 1991 and 2000, and three subpopulations. All of the occurrences are located outside of protected areas. The two occurrences in Estuaire province are threatened by shifting agriculture and wood harvesting (two locations). The three occurrences in Ogooué-Lolo province are located within two different forest concessions, and are, therefore, threatened by logging (two locations). All activities induce a decline in the extent and quality of the habitat of this species. As a consequence, these six occurrences represent four locations (cf. IUCN Standards and Petitions Committee 2022) with regard to the most serious plausible threat (logging). Drypetes aphanes is therefore assigned a preliminary status of ‘Endangered’ [EN 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).