Pauridiantha principensis Salvator NTORE & Olivier LACHENAUD 2019, sp. nov.
Creators: name: Salvator NTORE
name: Olivier LACHENAUD
Publisher: name: Zenodo
Year: 2019
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Gentianales
Rubiaceae
Pauridiantha
Pauridiantha principensis

description: Pauridiantha principensis Ntore & O.Lachenaud, sp. nov.
(Fig. 5)
Ramis robustis glabris quam stipulis latioribus, foliis subtus dense reticulatis, inflorescentiis laxe cymosis, calyce truncato vel minute lobato P. insulari et P. chlorantha, comb. nov. similis, sed ab ambabus foliis domatiis carentibus et nervis lateralibus valde adscendentibus differt. A P. insulare stipulis glaberrimis (nec sparse pubescentibus) et pedicellis longioribus sub flore 3.5-5 mm longis (nec 2-3 mm) et sub fructu 7.5-10 mm longis (nec 4-7.5 mm) etiam differt; a P. chlorantha, comb. nov. pedunculis ad apicem (nec ad medium vel quartum inferiore) prophyllis munitis, ovarioque basi 2-loculare et apice spurie 4-loculare (nec basi 4-5-loculare et apice spurie 8-10-loculare) etiam distinguitur.
TYPUS. — Príncipe. Plateau avant le Pico do Príncipe, 9.XII.1998, Oliveira 192/98 (holo-, BRLU!).
PARATYPUS. — Príncipe. Caminho do Morro de Leste, 5.IX.1999, Oliveira 149/99 (BRLU!).
ETYMOLOGY. — The species is named after Príncipe Island, where it is endemic.
DISTRIBUTION. — Endemic to Príncipe Island (Fig. 4) where apparently restricted to the highest areas near the peak; only collected twice and presumably uncommon.
HABITAT. — High forest, 675-750 m in altitude.
PHENOLOGY. — Flowers and immature fruits in September and December.
PRELIMINARY CONSERVATION ASSESSMENT. — Vulnerable (VU D2). Pauridiantha principensis, sp. nov. is endemic to Príncipe Island and occurs in submontane forest; it is only known from two specimens, representing two subpopulations. Its extent of occurrence (EOO) therefore cannot be estimated, while its area of occupancy (AOO) is estimated to be 8 km 2, within the limit for Critically Endangered status under criterion B2. Its range entirely lies within a protected area, and its two subpopulations occur in places difficult to access and unlikely to be directly impacted by human activities. However, the potential impacts of climate change on Principe’s submontane forest represent a plausible threat that could drive this species to CR or EN in a very short time, so it is assessed as Vulnerable (VU D2).
AFFINITIES. — This species seems closely related to P. insularis (Hiern) Bremek. from the neighbouring island of Saõ Tomé, and also to P. chlorantha, comb. nov. from Tanzania. All three species have robust and glabrous twigs that are wider than the stipules, densely reticulate tertiary leaf veins, truncate or minutely lobed calyces, and laxly cymose inflorescences. The new species differs from P. insularis by its longer pedicels and entirely glabrous vegetative parts (in P. insularis the stipules, and often also the petioles, have sparse appressed hairs), from P. chlorantha, comb. nov. by the number of ovary locules and the peduncles bearing prophylls at their apex rather than around the middle, and from both species by its much more ascending (and usually fewer) secondary leaf veins that lack domatia in their axils (Table 2).
Shrub (?)
Twigs slightly 4-sulcate when dry, 2.5-5 mm thick, glabrous.
Stipules
± tardily caducous, lanceolate, 5-7 × 1-1.5 mm, markedly thickened with margins recurved inwards, narrower than the twig, glabrous.
Leaves
Petiole. 1.5-3 cm long, glabrous.
Leaf-blade. Elliptic or slightly obovate, 17-23 × 7-11 cm, acute to obtuse at base, acuminate at apex with acumen 0.3-1 cm long, coriaceous, entirely glabrous, drying olive green to grey-green; midrib impressed above; secondary veins 8-11 pairs, ± uniformly curved and strongly ascending, forming inconspicuous loops near the margin; tertiary veins prominently reticulate below, forming areolae 1-1.5 mm in diameter.
Domatia. Absent.
Inflorescences
Axillary, solitary in each axil, laxly cymose, 6-14-flowered, 3-6 cm long, minutely and very sparsely pubescent.
Peduncle. 1-2.4 cm long, with a pair of stipulate prophylls c. 3 × 0.5 mm at apex.
Floral bracts. Absent.
Flowers
(4-)5-merous (see Fig. 5 F-H).
Pedicel. 3.5-5 mm long, slender, glabrous.
Calyx. Cupuliform, shortly and sparsely puberulous on both sides, with a tube 0.5-1 mm high, truncate or with minute triangular lobes 0.2-0.3 mm long, lacking colleters.
Corolla. Colour not known. With barrel-shaped to ± cylindrical tube 3-5 × 1.5-2 mm, puberulous in the upper half outside, densely villose in the upper half inside, and triangular lobes 2.5-3 × 1.3-2 mm, puberulous outside at least near the apex, papillate inside.
Floral bud. Subcylindrical, acute at apex.
Stamens. Exserted with filaments c. 1.8 mm long in brevistylous flowers, included with filaments 0.2-0.3 in longistylous flowers, anthers elliptic-oblong, c. 1.7 × 0.7 mm (including sterile appendage 0.2-0.3 mm).
Disk. ± domed, c. 0.5 mm high, with 5 lateral grooves and 10 apical fossulae formed by the imprints of the stamens, minutely papillose.
Ovary. 2-locular below, 4-locular by false septa in the upper part, c. 1 mm high, sparsely puberulous.
Style. Included, c. 2 mm long in brevistylous flowers, or exserted, c. 3.6 mm long in longistylous flowers, including the bilobed stigma c. 0.9 mm long, shortly pubescent except at base.
Fruits
Only known when very young. Subglobose, c. 3.5 mm in diameter, minutely and sparsely puberulous, crowned with persistent calyx; pedicels slightly accrescent in the fruiting stage, 7.5-10 mm long.
Seeds
Unknown.
REMARKS
The habit of P. principensis, sp. nov. and the colour of its flowers are not recorded, but it is presumably a shrub, like P. insularis and most other species of the genus.
description: Published as part of Salvator NTORE & Olivier LACHENAUD, 2019, Two new species and a new combination in the genus Pauridiantha Hook. f. (Rubiaceae) from tropical Africa, pp. 29-40 in Adansonia 41 (4) on pages 38-39, DOI: 10.5252/adansonia2019v41a4, http://zenodo.org/record/2653394