Rudgea bolivarensis Steyermark (1967: 415)

Lachenaud, Olivier, Bruniera, Carla P. & Zappi, Daniela C., 2022, The Rudgea hostmanniana complex (Rubiaceae) in the Guiana Shield region, Phytotaxa 561 (3), pp. 219-242 : 226-227

2. Rudgea bolivarensis Steyermark (1967: 415) . Fig. 1A , 2A

Type: — VENEZUELA. State of Bolivar, Gran Sabana, along wooded portion of quebrada tributary to Río Kukenan , south of Mount Roraima , 1005–1065 m, 2 October 1944 (fr.), J.A. Steyermark 59118 (holotype, VEN! [ VEN15991 ] ; isotype, NY! [ NY00133207 ]) .

Much-branched shrub or tree 3–15 m tall; twigs 3–5 mm thick, glabrous, soon covered with a pale buffish-straw bark. Stipules 3.5–5 × 3–10 mm, glabrous, marcescent but soon damaged, consisting of a ± truncate sheath (usually split at flower-bearing nodes) bearing on each side of the node a dense mass of 10–25 thick aculeiform dorsal appendages 1–1.3 mm long, shorter than the sheath and inserted between 1/3 and 2/3 of its length from the base. Leaves opposite; petioles 0.3–2 cm long, glabrous; blades elliptic, 4–18.5 × 1.8–9 cm, acute to rounded at base, obtuse to hardly acuminate at apex, very coriaceous with thickened margin, entirely glabrous, drying olive brown to olive green; midrib slightly concave above; secondary veins 7–12 on each side of midrib, moderately ascending, forming irregular loops 1.5–8 mm from the margin; tertiary venation densely reticulate and prominent below (at least in the dry state); domatia absent. Inflorescences terminal, in rather lax panicles, 6.5–14 cm long, erect, minutely spreading-puberulous (the peduncle ± glabrous); peduncle terete, 4.5–8.5 cm long; branched portion 1.5–5.5 × 3.5–7.8 cm; secondary branches 3–4 per node, 0.4–2.8 cm long; bracts minute, ca. 0.7 x 0.5 mm long, triangular to linear, puberulous. Flowers sessile, 5(–6)- merous. Hypanthium cylindrical, 0.7 mm long, glabrous. Calyx tube extremely reduced, lobes triangular to narrowly elliptic, 0.5–1 × 0.3–0.5(–1) mm, obtuse to acute at apex, glabrous or minutely ciliate at apex. Corolla only known in young bud stage; tube glabrous outside, villose at distal portion inside; lobes not dorsally corniculate, glabrous outside. Stamens not seen. Disk shortly cylindrical, 0.3 mm long, glabrous. Style not seen. Fruits obovoid to ellipsoid, 5.5–9 × 4–6 mm when dry, green when immature, bright orange when mature, glabrous, sessile or with pedicel <1 mm long, crowned by the persistent calyx 1.5–2 mm in diameter, i.e. not markedly accrescent. Pyrenes plano-convex, hemiobovoid, 6–8 × 4.5–5.5 mm, dorsal side faintly ridged with 3–4 dorsal and 2 lateral ridges, smooth between the ridges, ventral side smooth. Seeds with a deep T-shaped ventral furrow.

Distribution and ecology: —This species occurs in southeastern Venezuela (Mt. Roraima area) and adjacent Guyana and Brazil ( Fig. 5 ), in forest/savanna edges, at 700–1100 m altitude.

Phenology: —Specimens with flower buds were collected in December; and with fruits in June-July (immature), October and December (mature or nearly so).

Notes: —The original description of this species was based on two specimens, one from Venezuela, and one from Brazil. Several additional specimens from Guyana have since been found, and represent a new record for the country. Strangely enough, two Guyanan specimens (Henkel et al. 5675, Henkel & Chin 5709) have coordinates falling in Brazil, which may be due to an error either of country or of coordinates reported on the label. Mature flowers are still unknown.

Zappi & Steyermark (2004: 808) included Rudgea bolivarensis in synonymy under R. hostmanniana , which is similar in inflorescence and fruit characters. The stipules of R. bolivarensis , however, are very different and diagnostic, bearing only dorsal appendages that are shorter than the sheath (all other species of the complex have the stipular appendages exceeding the sheath, except R. coussareoides , which is easily recognized by its ternate leaves). Rudgea bolivarensis also differs from R. hostmanniana by having the corolla glabrous outside, leaves more coriaceous with a conspicuously thickened margin and an evident tertiary venation, and pyrenes with much less prominent dorsal ridges. The supposed differences in inflorescence structure, mentioned by Steyermark (1967), are actually not reliable; he described the pedicels of R. bolivarensis as 5–8 mm long, but the flowers are sessile and the fruits are sessile or subsessile (pedicel <1 mm long).

Additional Specimens Examined: — BRAZIL. Roraima [“ Rio Branco ”]: along igarapé 5 km SE of Serra Sabang, 720 m, 16–18 December 1954 (fl. buds & fr.), B. Maguire & C. K. Maguire 40276 ( NY, VEN) .

GUYANA. Pakaraima Mountains , Upper Ireng R . watershed, Malakwalai-Tipu, 300 m downslope from NE escarpment, 4°48’N, 60°18’W, 1100 m, 17 July 1994 (imm. fr.), T. W . Henkel, M . Chin & L . Williams 5675 ( CAY, U); Pakaraima Mountains , upper Ireng River watershed, E bank Kaalmang River at base of Achiknang, 4°59’N, 60°08’W, 700 m, 19 July 1994 (imm. fr.), T. W . Henkel & M . Chin 5709 ( K); Pakaraima Mountains , upper Ireng River, hills 2–3 km E of Cipo settlement, 4°48’N, 60°2’W, 760 m, 12 October 1994 (fr.), P . Mutchnik, T. W . Henkel & L . Williams 1 ( K); Northern Pakaraimas , Koa Valley, Annuyeng Creek from mouth to falls, 4°39’48”N, 59°48’33”W, 834 m, 10 June 1995 (imm. fr.), P . Mutchnick 1620 ( K) .

Figures

FIGURE 1. Stipules in the Rudgea hostmanniana complex.A, R. bolivarensis; B, R. coussareoides; C, R. cornigera; D, R. hostmanniana subsp. hostmanniana; E, R. maypurensis; F, R. tanaosepala. A from Mutchnick 1620 (K), B from Diaz et al. 7727A (K), C from Schulz 7539 (U), D from Lachenaud 1011 (BR), E from Williams 12972 (K), F from Clarke & Hoffman 584 (U). Drawing by O. Lachenaud.

FIGURE 2. Calyx and corolla in the Rudgea hostmanniana complex.A, R. bolivarensis, calyx; B, R.coussareoides, calyx; C, R. cornigera, flower bud; D, R. hostmanniana subsp. hostmanniana, flower bud; E, R. maypurensis, flower bud; F, R. tanaosepala, flower bud. A from Henkel 5675 (U), B from Liesner 24924 (K), C from Procter 4769 (U), D from Lachenaud 981 (BR), E from Plowman 13733 (K), F from Clarke & Hoffman 584 (U). Drawing by O. Lachenaud.

FIGURE 5. Distribution of Rudgea billietiae (black triangles), R; bolivarensis (grey circles), R. cornigera (black squares), R. pungens (grey squares) and R. tanaosepala (grey triangles).