Paracephaelis aristata De Block 2022, sp. nov.
Creators: name: Block, Petra De
Publisher: name: Zenodo
Year: 2022
Subjects: Biodiversity
Taxonomy
Plantae
Tracheophyta
Magnoliopsida
Gentianales
Rubiaceae
Paracephaelis
Paracephaelis aristata

description: Paracephaelis aristata De Block sp. nov.
urn:lsid:ipni.org:names:77260704-1
Fig. 5
Diagnosis
Differing from Paracephaelis saxatilis by having narrowly obovate leaves (vs elliptic, ovate, rarely obovate or orbiculate), longer and oblong calyx lobes in flowering stage (2.5–5 mm vs 0.8–1.5 mm long and triangular), and glabrous inner calyx surfaces (vs densely covered with long appressed hairs).
Etymology
The specific epithet refers to the aristate leaf apex.
Type material
MADAGASCAR – Toliara Province, Anosy Region, Taolagnaro District • Ambatorongorongo, Amboavola, Sarisambo; 297 m a.s.l.; 7–10 Jun. 1999; fr; Rabenantoandro, Randrihasipara & Ramisy 115; holotype: MO scan; isotypes: BR [BR000000906218], K n.v., P [P00274306] n.v., TAN n.v.
Description
Shrub, ca 2 m tall; pubescence tawny. Young shoots brownish, densely covered with ± short appressed hairs; older branches pale greyish or fawnish, glabrous; internodes short, 0.3–2 cm long. Petioles 2–6 mm long, densely covered with ± short appressed hairs. Leaf blades narrowly obovate, (1.2–)1.5–5.5 × 0.5– 1.5 cm, thickly coriaceous, drying brown and not discolorous, upper surface glossy and glabrous, lower surface densely covered with long erect or spreading hairs (but ± appressed on midrib); base attenuate; tip shortly aristate; domatia absent; 4–7 secondary veins on each side of midrib, inconspicuous above, raised below; higher order venation inconspicuous on both surfaces. Stipules triangular with needle-like awn, outer surface densely covered with ± short appressed hairs, inner surface glabrous with row of colleters at the base; sheath 1–2 mm long; awn 2–4 mm long. Inflorescences sessile, 1–2 × 1.5–3 cm, with (3–)5–15 flowers; inflorescence parts densely covered with ± short appressed hairs; first order axes 0.2–1.5 cm long; higher order bracts with stipular parts reduced or absent, foliar parts narrowly triangular and vaulted, 5–10 mm long, or, linear leaf-like, up to 15 mm long; bracteoles on pedicel just below ovary, opposite, stipular parts absent, foliar parts narrowly triangular, 3–5 mm long, tips acute. Flowers sessile or shortly pedicellate, pedicels 0–3 mm long (in fruiting stage). Calyx densely covered with appressed to spreading hairs outside, inner surface glabrous; tube ca 1 mm long in flowering stage, ca 2 mm long in fruiting stage; lobes oblong, often somewhat unequal in length, 2.5–3 mm long in flowering stage, 4–5 mm long in fruiting stage, tips rounded with small acumen. Mature corolla, stamens, style and stigma unknown. Ovary 1.5–2 mm long, densely covered with spreading hairs; per locule 6–10 ovules arranged at periphery of placenta attached to upper half of septum. Fruits spherical, ca 1 cm in diam., glossy (when dried), densely covered with spreading hairs. Mature pyrenes and seeds unknown.
Distribution
Only known from Ambatorongorongo Mountain in Taolagnaro District, Anosy Region (Toliara Province) (Fig. 23A).
Habitat and phenology
Low-elevation forest; elev. ca 300 m. Flowers: unknown; Fruits: June.
Vernacular name
Mantsaka (Rabenantoandro et al. 115).
Provisional IUCN assessment
Critically Endangered: CR B2ab(iii). Paracephaelis aristata sp. nov. is only known from a single collection, which means that the extent of occurrence (EOO) cannot be calculated. The area of occupancy (AOO) is 4 km 2, which complies with the Critically Endangered category under criterion B2. The species occurs in a single location, which complies with the Critically Endangered category under subcriterion ‘a’ of criterion B2. The only material was collected in 1999 on Ambatorongorongo Mountain, located ca 25 km W-SW of Taolagnaro. This isolated mountain close to Ranopiso can be viewed as the southernmost extension of the Anosyennes Mountains (Nussbaum & Raxworthy 1994). In south-eastern Madagascar, littoral, lowland, and montane humid, as well as dry forest come together (Goodman et al. 1997). In between those different forest types, transitional forests with intermediate characteristics exist. These forests have a high conservation priority (Nicoll & Langrand 1989; Ganzhorn et al. 1997). The Ranopiso region hosts many endemic species of reptiles and amphibians (Ganzhorn et al. 1997) and the forest on Ambatorongorongo Mountain is known for its high species richness and local endemism for lemurs, amphibians, and reptiles (Ramanamanjato et al. 2002). It is highly likely that the same is true for plant species. At least one other species of Rubiaceae is only known from Ambatorongorongo, notably Flagenium pedunculatum Ruhsam & A.P.Davis (Ruhsam & Davis 2007). Ambatorongorongo Mountain and surrounding regions were once completely forested but the ever-increasing human pressure resulted in destruction and degradation of the forests to a point where now only isolated forest patches remain in between rice paddies, fields, and lands used for pasturage (Ramanamanjato et al. 2002). The forests on Ambatorongorongo Mountain are not protected but are of a high conservation priority (Ramanamanjato et al. 2002). Since Paracephaelis aristata sp. nov. is only known from this one location outside of a protected area in a region where deforestation continues even now, the species is assessed as Critically Endangered.
Note
This species is only known from the type. Flowers have not been collected. Label information on Rabenantoandro et al. 115 indicates the habitat as “forêt de transition”.
description: Published as part of Block, Petra De, 2022, Monograph of the western Indian Ocean genus Paracephaelis (Rubiaceae - Pavetteae), with description of thirteen new species, pp. 1-99 in European Journal of Taxonomy 801 on pages 23-25, DOI: 10.5852/ejt.2022.801.1685, http://zenodo.org/record/6358810