Rudgea leucocarpa O. Lachenaud, 2022

Lachenaud, Olivier, Bruniera, Carla P. & Zappi, Daniela C., 2022, Six new and a little-known species of Rudgea (Rubiaceae-Palicoureeae) from the Guianas, Phytotaxa 531 (3), pp. 154-174 : 171-173

Rudgea leucocarpa O. Lachenaud , sp. nov. ( Fig. 10 )

Fructibus albis vel luteis apice truncato calyce remnante in diametro valde accrescente, pyrenis dorso leviter verrucosis, stipulis brevibus (2-4 mm longis) margine fimbriatis dorso exappendiculatis, foliis glaberrimis costa mediana supra prominente, inflorescentiis glomerulatis vel brevissime ramosis, inter congeneribus satis recedit.

Type: — FRENCH GUIANA: Sommet Tabulaire [Mount Itoupé], versant sud,> 50 km SE de Saül, 24 August 1980 (fr.), J.J. de Granville 3587 (holotype, P [P06800583]; isotypes, CAY [CAY079068, CAY079069], NY n.v.) .

Rudgea sp. B auct. ( Boom & Delprete 2002: 646).

Shrub 0.2 – 2 m tall, much branched; terminal branchlets 1.5 – 2 mm thick, glabrous, long remaining green. Stipules consisting of two flat interpetiolar portions, ovate to triangular, 2 – 4 × 2 – 4 mm, irregularly laciniate with 7 – 10 marginal appendages 0.6 – 1.5 mm long and lacking dorsal appendages, glabrous, marcescent and soon corky, surrounding a very fugacious internal sheath 1 – 2(– 3) mm long. Leaves opposite, petiolate; petiole 0.6-1.5 cm long, glabrous; blades elliptic, 8 – 18.5 × 3 – 7.3 cm, acute at base, narrowly and usually long acuminate at apex, coriaceous or papyraceous when dry, entirely glabrous, drying olive green with shiny underside, midrib convex on both sides, secondary veins 7 – 10 on each side of midrib, weakly to moderately ascending, forming very conspicuous loops 2 – 7 mm from the margin; tertiary veins prominent at least when dry, laxly reticulate, forming areolae ca. 3 mm in diameter; domatia absent. Inflorescences terminal, glomerulate or sometimes very shortly branched, few-flowered, erect, glabrous; peduncle terete, 3 – 9 mm long; main ramifications (when present) 2 per node, 0 – 2 mm long; bracts shortly triangular, 1.5 mm long, glabrous. Flowers sessile, 5-merous, whether distylous unknown. Hypanthium tronco-conical, 1.5 mm long, glabrous. Calyx tube 0.7 mm long, glabrous; lobes triangular, 1 – 1.5 mm long, acute at apex, patent. Corolla unknown. Fruits subglobose to broadly ovoid, 13 – 20 mm in diam. when fresh, 11–16 × 11–15 mm when dry, green when immature, white to yellow when mature, glabrous, sessile; calyx scar much enlarging on fruit, 5–9 mm wide. Pyrenes ellipsoid to ovoid, 10.5 – 12 × 8 – 9 mm, slightly verrucose, with one weak dorsal ridge; seeds with a deep, ± T–shaped ventral groove.

Distribution and ecology: —This species occurs in northern Brazil (Reserva Biologica Uatumã in Amazonas state), extreme southeastern Suriname (Tumuc Humac Mts) and French Guiana, where it is found mostly in the central and southern hill ranges (Tumuc Humac Mountains, Montagne Bellevue de l’Inini, Mount Galbao, Mount Itoupé) with one record in the Approuague River basin in the northeast ( Fig. 9 ). It occurs in lowland forests, and mostly in submontane forests on ridges where locally not uncommon, at 350–730 m in elevation.

Phenology: —Immature fruits collected in January and March; mature fruits in August and early September.

Conservation status assessment:—Least Concern (LC). Rudgea leucocarpa occurs in French Guiana, Suriname and northern Brazil (state of Amazonas), and is known from 13 collections representing eight occurrences. Its extent of occurrence (EOO) is calculated to be 39,915 km ², exceeding the limit for Vulnerable status under subcriterion B1, and its area of occupancy is estimated to be 32 km ², within the limit for Endangered status under subcriterion B2. Four of its occurrences are protected in the Parc Amazonien de Guyane, French Guiana, and in the Reserva Biologica Uatumã, Amazonas state, Brazil. The other occurrences are in areas sparsely populated and difficult to access, where there is no evidence of a particular threat. Consequently, the species is here assessed as LC.

Notes: —This species is quite distinct from all other so far recorded in the Guianas, though in the absence of flowers it is difficult to suggest any affiliation with other species of the genus. The large white to yellow fruits with a conspicuously enlarged calyx scar are especially diagnostic (species of Rudgea occurring in the Guianas have mostly red or orange fruits, or if white, much smaller). In this character, and also in the leaves, pyrenes, seeds and inflorescences, Rudgea leucocarpa resembles Carapichea verrucosa C.M. Taylor (in Taylor & Gereau 2013: 124) from western Amazonia ( Peru, Colombia, Brazil), although the latter has even larger fruits (2.5 – 3 × 2 – 2.5 cm) with a distinctly warty surface, and its stipules are distinctly longer than broad and apparently not fimbriate. Both species are known from fruiting material only, and have never been studied phylogenetically, so it is unclear whether their resemblance is superficial or indicative of a true relationship. Carapichea verrucosa is unusual in its genus and its position remains uncertain, although the stipules seem to exclude it from Rudgea . In vegetative characters R. leucocarpa also shows a superficial resemblance to R. graciliflora , but the latter has smaller fruits with the calyx not enlarged and a purplishbrown (when immature) or orange-red (when mature) colour, the leaf midrib concave above, and the stipules with a dorsal keel bearing apical appendages, while those of R. leucocarpa are dorsally flat and marginally fimbriate.

This species was already recognized as probably new by Boom & Delprete (2002: 646). The inflorescences, described by these authors as paniculate, are in fact more commonly glomerulate (the ramifications, if present, being very short). The internal sheath of the stipules apparently tends to disintegrate early in their development, and is often not visible on herbarium material. According to the label of Bordenave 1248, the texture of the fruits is reminiscent of marshmallow paste (“pâte de guimauve”).

Additional specimens examined (paratypes): — FRENCH GUIANA. Saut Tortue , 4°11’N, 52°24’W, 17 November 1994 (fr.), B. Bordenave 1248 (P); Tumuc Humac, forêt dense sur la crête du Mitaraka sud, à 1,5 km environ à l’ouest du sommet, 17 August 1972 (fr.), J.J. de Granville 1280 ( CAY); Monts Galbao, à 10 km WSW de Saül, 14 March 1973 (imm. fr.), J.J. de Granville 1536 ( CAY, P); Pente NE des Monts Galbao, 11 March 1975 (imm. fr.), J.J. de Granville 2386 ( CAY, P) . Montagne Bellevue de l’Inini , extrémité SW, versant NW, 15 August 1985 (fr.), J.J. de Granville, L. Allorge, G. Cremers, A.R.A. Görts-van Rijn & J.F. Kodjoed 7525 ( CAY); Montagne Bellevue de l’Inini , zone orientale, versant sous le vent, 28 August 1985 (fr.), J.J. de Granville, L. Allorge, G. Cremers, A.R.A. Görts-van Rijn & J.F. Kodjoed 7858 ( CAY); Montagne Bellevue de l’Inini , zone centrale, 8 September 1985 (fr.), J.J. de Granville, L. Allorge, G. Cremers, A.R.A. Görts-van Rijn & J.F. Kodjoed 8109 ( CAY); Mont Galbao , secteur Sud, 3°35’N, 53°20’W, 22 January 1986 (imm. fr.), J.J. de Granville, C. Feuillet, L. Hollenberg, O. Poncy & H. Sangray 8912 ( CAY); same locality, 27 January 1986 (imm. fr.), J.J. de Granville, C. Feuillet, L. Hollenberg, O. Poncy & H. Sangray 9002 ( CAY) .

SURINAME. Tumuc Humac Mts , Talouakem, 2°31’N, 54°45’W, 9 August 1993 (fr.), P. Acevedo-Rodriguez, J.J. de Granville, L . Hollenberg, A. Joly & C. Avril 5969 ( CAY); Tumuc Humac , frontière Brésil – Surinam, brousse et forêt basse sur le sommet du Paloulouiméenpeu, 2 August 1972 (fr.), J.J. de Granville 1087 ( CAY) .

BRAZIL. Amazonas. Mun. Presidente Figueiredo, Rebio [Reserva Biologica] Uatumã, grade do PPBio, Baixio, 10 July 2008 (fr.), J.F. Stancik, S. Sakagawa, M.S. Tavares, R. L. da Silva & F.C. Costa 449 (K) .

Figures

FIGURE 9. Distribution of Rudgea jadinii (circles) and R. leucocarpa (triangles).

FIGURE 10. Rudgea leucocarpa. A, fruiting branch; B–D, stipules; E, fruit; F, pyrene, dorsal view; G, seed, cross-section.A, E–G from Granville 3587, B–C from Granville 1280, D from Granville 2386. Drawn by O. Lachenaud.