Paracephaelis sambavensis De Block, 2022

Block, Petra De, 2022, Monograph of the western Indian Ocean genus Paracephaelis (Rubiaceae - Pavetteae), with description of thirteen new species, European Journal of Taxonomy 801, pp. 1-99 : 65-67

Paracephaelis sambavensis De Block sp. nov.

urn:lsid:ipni.org:names:77260715-1

Fig. 17

Diagnosis

Differing from Paracephaelis orientalis sp. nov. by having larger leaves (13–18 × 5.5–8.5 cm vs 4.5– 10.5 × 1–4 cm), larger inflorescences (4–8 × 4–8 cm vs 1.5–4 × 2–5 cm), longer pedicels (1–2 mm long in flowering stage, up to 5(–8) mm long in fruiting stage vs flowers sessile), shorter bracteoles (ca 1 mm vs 1.5–2 mm long), shorter calyx tubes (1–1.5 mm long vs 1.5–2 mm long in flowering stage, ca 3 mm long in fruiting stage), fewer ovules per locule (3–4 vs 4–7), and ovoid fruits (vs spherical).

Etymology

The species epithet is based on the type locality of the species.

Type material

MADAGASCAR – Antsiranana Province, Sava Region, Sambava District • S de Sambava ; 1–10 Apr. 1967; fr; Capuron 27702-SF; holotype: P; isotypes: BR [ BR0000022757685 ], TEF .

Other material studied

MADAGASCAR – Antsiranana Province, Sava Region, Sambava District • S de Sambava; 30 Nov.– 1 Dec. 1966; fl; Capuron 27121-SF; BR, P, TEF .

Description

Tree to 15 m tall; pubescence tawny. Young shoots pale brown, densely covered with short appressed to spreading hairs; older branches pale brown, somewhat flaking, glabrescent. Petioles 1.2–2 cm long, densely covered with short appressed to spreading hairs. Leaf blades elliptic or obovate, 13–18 × 5.5– 8.5 cm, thinly coriaceous, drying brown or dark brown and hardly discolorous, upper surface glossy, both surfaces glabrous (except for pubescence on midrib and secondary veins); base cuneate; tip acuminate with acumen 0.8–1.8 cm long; hair tuft domatia present; midrib moderately to densely covered with short appressed hairs in the lower half, sparsely covered with short appressed hairs or glabrous in the upper half on both surfaces; 8–12 secondary veins on each side of midrib, raised and sparsely covered with short appressed hairs or glabrous on both surfaces; higher order venation visible on both surfaces (when dried). Stipules triangular, 5–8 mm long, gradually tapering into an acute tip or with short awn <1 mm long, outer surface densely covered with short appressed to spreading hairs, inner surface glabrous with 2–3 rows of colleters at the base. Inflorescences sessile, 4–8 × 4–8 cm, with numerous flowers; inflorescence parts densely covered with short appressed to spreading hairs; first order axes 1–3 cm long; higher order bracts with stipular parts reduced or absent, foliar parts triangular and vaulted, 2–10 mm long; bracteoles on pedicel just below ovary, opposite, stipular parts absent, foliar parts triangular, ca 1 mm long, tips acute. Flowers shortly pedicellate; pedicels 1–2 mm long in flowering stage (immature buds), up to 5(–8) mm long in fruiting stage. Calyx densely covered with short appressed to spreading hairs outside; tube 1–1.5 mm long, inner surface with ring of long appressed hairs at the base and glabrous higher up; lobes quadrangular, ca 1 × 1 mm, somewhat keeled, inner surface glabrous, margins ciliate, tips rounded. Mature corolla, stamens, style and stigma unknown. Ovary 1–1.5 mm long, longitudinally ribbed (when dried), densely covered with short appressed or spreading hairs; per locule 3–4 ovules arranged at periphery of placenta (mostly at base and top) attached just above middle of septum. Fruits ovoid, 8–10 × 5–8 mm, moderately covered with short appressed to spreading hairs; fruit wall well-developed with multi-layered anastomosing network of sclerified vascular bundles; pyrenes hemi-ovoid, 7–9 × 4–5.5 mm, crustaceous adaxially, ± stony abaxially, with rounded base, shortly acuminate tip, small adaxial opening somewhat above the middle and longitudinal central ridge running from the apex to the top of the adaxial opening. Seeds (1–)2–4(–8) per fruit, 4–4.5 × 3.5–4 mm.

Distribution

Coastal species, only known from Sambava in Sambava District, Sava Region (Antsiranana Province) ( Fig. 23D ).

Habitat and phenology

Littoral forest; on sand. Flowers: November (flowers buds); Fruits: April.

Provisional IUCN assessment

Critically Endangered: CR B2ab(iii). Paracephaelis sambavensis sp. nov. is only known from 2 specimens, seemingly collected from the same tree with a time lapse of ca 5 months. As a result, the EOO cannot be calculated and the AOO is 4 km 2, which complies with the Critically Endangered category under criterion B2. The species is known from a single location, which also complies with the Critically Endangered category under subcriterion ‘a’ of criterion B2. Both collections date from the sixties and no recent specimens are known. Paracephaelis sambavensis sp. nov. is a large tree from littoral forests on sand in north-eastern Madagascar. These eastern littoral forests on sand were identified as one of the most biodiverse habitats for plants ( Dumetz 1999). They are home to ca 13% of Madagascar’s native plant species, even though they only occupy less than 1% of Madagascar’s surface ( Consiglio et al. 2006). While littoral forests formed a continuous band along the east coast of Madagascar in the past, less than 10% now remain as isolated and fragmented patches ( Consiglio et al. 2006). All remaining littoral forests are under severe pressure from local communities through logging for construction and firewood ( Consiglio et al. 2006), and this would certainly be the case around a large city as Sambava. As a large tree (15 m tall), P. sambavensis sp. nov. would certainly be a sought-after resource. Furthermore, littoral forests in the region of Sambava have been cleared for slash-and-burn agriculture as well as for large-scale oil palm plantations (Google Earth, September 2020). Only a few remnant patches of littoral forest remain. Based on the above-mentioned facts, a reduction in the extent and quality of the habitat of P. sambavensis sp. nov. is inferred. This threat, combined with the low AOO and the single location, qualifies P. sambavensis sp. nov. for Critically Endangered status. The fact that the species has not been collected or observed for more than fifty years, would suggest it is possibly extinct. A targeted survey in the littoral forests of northern and north-eastern Madagascar is needed to confirm or deny the suspicion that the species is extinct in the wild. If living plants of this species were to be found, they should be protected and an ex situ conservation program set up.

Note

Since the collection labels give identical data for both Capuron 27702-SF and 27121-SF, it would seem that the two specimens were collected from a single tree, the collector returning to the locality to collect flowers after having found a specimen in fruit. This species was never collected again.

Figures

Fig. 17. Paracephaelis sambavensis De Block sp. nov.A. Fruiting branch. B. Stipule. C. Bracteoles, ovary and calyx. D. Fruit. E. Pyrene, adaxial view. Drawn by Mr A. Fernandez. From Capuron 27702-SF (A, C–E) and Capuron 27121-SF (B).

Fig. 23. Distribution maps of Malagasy species of Paracephaelis. A. P. aristata De Block sp. nov. (black dot), P. bardotiae De Block sp. nov. (blue dot), P. capitulifera De Block sp. nov. (green dot), P. gautieri De Block sp. nov. (red dot), and P. grandifructa De Block sp. nov. (yellow dot). B. P. cinerea (A.Rich. ex DC.) De Block (black dot). C. P. longipedicellata De Block sp. nov. (black dot), P. orientalis De Block sp. nov. (blue dot), P. pauciflora De Block sp. nov. (green dot), P. ranirisonii De Block sp. nov. (red dot), and P. seyrigii De Block sp. nov. (yellow dot). D. P. russata De Block sp. nov. (black dot), P. sambavensis De Block sp. nov. (blue dot), P. saxatilis (Scott Elliot) De Block (green dot), P. sericea (Arènes) De Block (red dot), and P. tiliacea Baill. (yellow dot).