Rudgea glomerulata Zappi & 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 : 159-162

Rudgea glomerulata Zappi & O. Lachenaud , sp. nov. ( Fig. 3 )

Stipulis et bracteis valde laciniatis, calyce tubo conspicuo 1.5 – 4 mm longo lobisque triangularibus, inflorescentiis pendulis et disco bipartito Rudgeae itoupensi valde similis, sed differt bracteis externis maioribus et angustioribus, 9 – 28 × 2.5 – 3.5 mm (vs. ca. 7 × 7 mm) apice longe acuminatis et calycibus valde excedentibus, corollaque tubo 18 – 20 mm longo (vs. 11.5 mm)

Type: — FRENCH GUIANA. Montagne de Kaw , route de Kaw, p.k. 46, 4°33’N, 52°09’W, 14 December 1986 (fl.), J.J. de Granville 9075 (holotype, MO [MO-2365274]; isotypes, CAY [CAY079168], P [P03985332], U [U 0130743]) .

Shrub, 1 – 3 m tall, much-branched; terminal branchlets 2–3 mm thick, densely pubescent with appressed hairs, soon covered with a pale brownish bark. Stipules consisting of two flat interpetiolar portions, narrowly ovate, 8 – 13 × 2 – 5 mm, deeply laciniate with 15 – 20 marginal appendages 1.5–5 mm long and lacking dorsal appendages, surrounding an internal sheath 2 – 3.5 mm long bearing ca. 10 lateral appendages 1.5 – 3 mm long in the axils of the petioles, pubescent, soon corky and eventually caducous. Leaves opposite, petiolate; petioles 0.5 – 2 cm long, pubescent like the stems; blades elliptic to narrowly obovate, 10.5 – 24 × 3 – 8 cm, acute to obtuse at base, acuminate at apex, the margin slightly revolute, papyraceous to slightly coriaceous when dry, glabrous above, pubescent below with sparse appressed hairs 0.2 mm long, drying olive green to olive brown; midrib convex on both sides, secondary veins 7 – 14 on each side of midrib, weakly ascending, forming loops at 1–5 mm from the margin; tertiary veins concolorous, prominently and rather laxly reticulate in the dry state; domatia absent. Inflorescences terminal, capitate to shortly branched, 4.5 – 15 cm long, many-flowered, ± pendulous, densely appressed hairy; peduncle terete, 2.5 – 13.5 cm long; flowering portion 1 – 3 × 2 – 5.5 cm; ramifications absent or very short (<1 mm) at anthesis, sometimes accrescent to 1 cm long in the fruiting stage; bracts green, numerous and long exceeding the calyces, the basal ones lanceolate, 9 – 28 × 2.5 – 3.5 mm, deeply and irregularly laciniate towards their base, the upper ones similar but narrower, 9 – 11 × 1.5 – 2 mm, all densely appressed hairy outside and glabrous inside. Flowers (4)5-merous, whether distylous unknown, sessile. Hypanthium tronco-conical to subcylindrical, 1 – 1.5 mm long, densely villose. Calyx deeply cupuliform, pubescent outside; tube 1.5 – 4 mm long; lobes triangular, 1 – 2 mm long, the apex acute but often damaged. Corolla white; tube narrow and almost cylindrical, 18 – 20 × 1.5 mm, glabrous throughout; lobes triangular, 4.5 – 6 mm long, broadly corniculate at apex, glabrous on both sides except the cornicula minutely puberulous. Stamens fully exserted; filaments exserted 3 mm beyond corolla mouth; anthers 2.5 × 0.4 mm, dorsifixed. Disk bipartite, cylindrical, 1 mm long, glabrous. Style included, 5 mm long, branches 1 mm long. Fruits ellipsoid to ovoid or rarely subglobose, 15 – 18 × 10 – 15 mm when fresh, 7.5 – 17 × 7.5 – 13 mm when dry, dark green when immature, pale yellow to yellow-orange when mature, glabrous, on short accrescent pedicel 2 – 5 mm long, crowned with persistent calyx tube; mesocarp yellowish-white. Pyrenes ellipsoid, 10.5 – 13.5 × 8 – 9 mm, the dorsal surface minutely verruculose, smooth; seeds with a deep T-shaped ventral furrow.

Distribution and ecology: —Only known from northern French Guiana, where it occurs mostly in the northeastern hill ranges (Montagne des Trois Pitons, Nouragues, and eastern side of the Kaw mountain) with an isolated record further west in the Sinnamary basin ( Fig. 4 ). The species occurs in the undergrowth of mature forest, at 90–400 m elevation.

Phenology: —The species was collected with flowers in November and December, corresponding to the beginning of the first rainy season. Immature fruits have been found in February (end of first rainy season) and mature ones from April to July (second rainy season).

Conservation status assessment:—Vulnerable (VU) (B1ab(iii)+2ab(iii)). Rudgea glomerulata is endemic to French Guiana, and is known from 16 collections, representing eight occurrences. Its extent of occurrence (EOO) is calculated to be 5,026 km ², within the limit for Vulnerable status under subcriterion B1, and its area of occupancy is estimated to be 40 km ², within the limit for Endangered status under subcriterion B2. Two of its occurrences are protected in the Réserve Naturelle des Nouragues and Réserve Naturelle des Marais de Kaw-Roura. The other occurrences are unprotected but most of them are found in remote areas with currently low level of threat. However, one on the Kaw Mountain is in an area experiencing some level of timber exploitation, and also harboring important bauxite and gold deposits; mining projects there were abandoned in 2008, but may resurface in the future. Another potential threat to this occurrence comes from touristic development and related infrastructure. We may therefore project a decline in habitat extent and quality. The eight occurrences represent eight locations in the sense of IUCN, and the species qualifies for Vulnerable status under the conditions B1ab(iii)+2ab(iii).

Notes: —This species is similar to R. itoupensis , described below; the two are remarkable in the genus by their deeply laciniate bracts and stipules (shallowly laciniate in most other species), ± pendulous inflorescences, welldeveloped calyx tube, and bipartite disk (the disk in Rudgea species is usually entire). It differs from R. itoupensis by its larger and narrower bracts that long exceed the calyces, and its longer corolla tube ( Table 2 ). The two species also have different geographical and altitudinal ranges. In view of their stipule morphology and fruit colour, these species probably belong to the informal “ lanceifolia clade” defined by Bruniera (2015).

Another species resembling R. glomerulata is Palicourea yneziae C.M.Taylor (Taylor 2015: 81) [Syn. Rudgea mexiae Standley (1936: 165) ] from Peru and southern Colombia. This species was recently transferred from Rudgea to Palicourea , although it is unusual in the latter genus – especially due to its fimbriate stipules – and its placement there is provisional (Taylor 2015: 59–60). Its stipules, bracts and calyces are quite similar to those of R. glomerulata , although the leaf venation, disk, and fruit colour are different in both taxa ( Table 2 ). In the absence of phylogenetical analysis including these species, it is unclear whether the resemblance between them is due to convergence or indicative of an affinity.

There is also some resemblance between R. glomerulata and R. lanceifolia , especially in the shape of the stipules, but the differences are numerous: R. lanceifolia is a taller plant 3-10 m high, with more strongly ascending secondary leaf veins, an erect and usually branched inflorescence, entire or shortly dentate bracts, a calyx divided almost to the base, a usually longer (17-80 mm) corolla tube that is pubescent on both sides, and fruits dark red when immature and black when mature, crowned with an entire markedly accrescent disk 2-3 mm long and 5-10 mm in diameter.

The inflorescences of Rudgea glomerulata are often capitate, but may have short ramifications, especially at the fruiting stage, as the rachis might expand after anthesis. It is not known whether the flowers are heterostylous; the only open flowers seen (on the type) are short-styled.

Two collections, one from the Pakaraima Mountains in Guyana, K.M. Redden, R. Williams, C. Perry, C. Paul & M. Lyle 1927 (P [P01019851]) and the another from Araracuara in Colombia, H. Vester & A. Matapi 754 (L.4195512]), very closely resemble R. glomerulata in characters of the bracts, inflorescences and stipules, as well as in leaf shape and venation, but have a hirsute (rather than appressed) indumentum on the petioles and lower surface of leaf veins. The former specimen also has a much shorter peduncle, while the latter appears to have an erect inflorescence. More material is required to decide whether these collections are conspecific or not with R. glomerulata .

Additional specimens examined (paratypes): — FRENCH GUIANA. Nouragues , 13 May 1985 (fr.), A. Cockle 101 ( CAY) ; Eastern Plateau of Montagne Tortue , 11 km WNW of Approuague River, 4°18’N, 52°22’W, 12 June 1988 (fr.), C. Feuillet 10045 (K) ; Station des Nouragues , 4°03’N, 52°42’W, 22 November 1989, (fl. buds), G. Cremers 10928 ( CAY) ; forêt sur la rive gauche de l’Arataye, à environ 2 km du Saut Pararé , 14 February 1969 (imm. fr.), J.J. de Granville 82 ( CAY, P) ; estuaire de l’Oyapock, entre le village de Petit Toucouchi et la montagne des Trois Pitons, 20 January 1981 (fallen fl.), J.J. de Granville 4279 ( CAY, P, U) ; Kaw : Montagne Favard, 20 April 1984 (fr.), J.J. de Granville 6880 ( CAY, MO) ; Montagne de Kaw , extrémité est, versant sud, 3 November 1985 (fallen fl.), J.J. de Granville 8245 ( CAY, MO) ; Station des Nouragues , 4°03’N, 52°42’W, 23 February 1991 (imm. fr.), J.J. de Granville 11173 ( CAY, MO) ; D.Z. de Crique Jupiter, bassin du Sinnamary , 24 April 1991 (imm. fr.), J.J. de Granville, C. Roesel & L. Brothers 11497 ( CAY) ; Station des Nouragues , 4°03’N, 52°42’W, June 1989 (fr.), D. Larpin 643 ( CAY) ; montée du Pic des Trois Pitons , 9 June 1980 (fr.), C. Moretti 1166 ( CAY, P) ; Nouragues Field Station , 4°05’N, 52°40’W, 27 February 2002 (imm. fr.), S.A. Mori, F. Blanchard & T.A. Lobova 25483 ( CAY, NY, P) ; Arataye (affluent de l’Approuague) au saut n°1, rive droite, 10 February 1969 (imm. fr.), R.A.A. Oldeman B-2127 ( CAY) ; Fleuve Arataye , Saut Pararé, 27 July 1984 (fr.), B. Riéra 659 ( CAY) ; station des Nouragues , bassin de l’Arataye, 4°03’N, 52°42’W, 11 July 1989 (fr.), D. Sabatier & M.-F. Prévost 2533 ( CAY, P, U) .

Figures

FIGURE 3. Rudgea glomerulata. A, flowering branch; B, stipules; C, outer bract, seen from outside; D, flower bud; E, flower (calyx removed); F, cross-section of calyx, disk and ovary; G, hypanthium, calyx and style; H, fruit; I, pyrene, dorsal view; J, seed, cross-section. A, C–G from Granville 9075, B from Granville 82, H from Moretti 1166, I–J from Larpin 643. Drawn by O. Lachenaud.

FIGURE 4. Distribution of Rudgea glomerulata (squares) and R. itoupensis (star).