Combretum rupestre Jongkind & Texier, 2019

Jongkind, Carel C. H. & Texier, Nicolas, 2019, Novitates Gabonenses 92: Combretum rupestre (Combretaceae), a new liana species from Mount Ngouadi in Gabon, Candollea 74 (1), pp. 9-14 : 12-14

Combretum rupestre Jongkind & Texier , spec. nova ( Fig. 2–4 ).

Holotypus: GABON: Ogooue-Lolo, Mount Ngouadi , [0°13'43"S 13°18'22"E], 778 m, fl., 5.III.2017, Texier et al. 622 ( MO!; iso-: BRLU!, G!, LBV!, P!, WAG!) .

Differs from all other Combretum species by the combination of a patelliform receptacle with the two series of stamens of unequal length, and by the receptacle, and leaves below, covered by a glutinous layer.

Liana. Leaves opposite; petiole c. 1 cm long, covered with many tiny erect hairs; blade 11–12 × 5–6 cm, both sides glutinous with tiny scales just visible in this glutinous layer; tiny, straight, erect hairs on first half of midrib above, and all larger nerves below; 8 –11 pairs of main lateral nerves with hairy domatia in the axil below; base rounded; apex acuminate. Scales circular in outline, 60–70 µm in diam, cells delimited by c. 8 radial walls, translucent. Infloresence a terminal panicle up to 14 cm long, or an axillary spike, branches covered with tiny hairs, bracts tiny, caducous. Flowers 4-merous, sessile; lower receptacle c. 1 mm high, glutinous; upper receptacle patelliform, c. 1.7 mm wide, glutinous outside, with a few scales visible in this glutinous layer; calyx lobes triangular in outline, 1.5 mm wide × 1 mm long, boat shaped, with a few ordinary hairs at the apex; petals spathulate, c. 1.5 × 0.5 mm, glabrous; stamens opposite the petals with filament c. 2 mm long, stamens alternating with the petals with filament c. 1 mm long, anthers c. 0.3 mm long; disk with glabrous surface and free, hairy edge; style c. 0.5 mm long, glabrous. Fruit unknown.

Habitat and distribution. – Only known from the type location on the edge of the plateau on Mount Ngouadi ( Fig. 3 ).

Conservation status. – Based on a 2 × 2 km grid cell size, the AOO of this species is estimated at 4 km ², which is under the limit for category “Critically Endangered” under criterion B2. The EOO is not calculated because this species is only known from one specimen (Texier 622) collected in 2017 in SEEF forestry concession, on the edge of the plateau on Mount Ngouadi. This specimen represents a single sub-population. Although the Mount Ngouadi area is located in a forestry concession, no plans are made for now to develop this activity in this part of the concession. The concession has even stopped its activity since end of 2017. Nevertheless, if forestry activities are finally undergone in this part of the concession, then the species is likely to be re-assessed as CR. In consequence, the species can be evaluated as “Vulnerable” [VU D2] following the IUCN Red List Categories and Criteria ( IUCN, 2012, 2017).

Figures

Fig. 2. − Combretum rupestre Jongkind & Texier. A. Leaves from above; B. Leaves from below; C. Inflorescence. [Texier et al. 622] [Photos: N. Texier]

Fig. 3. – Map of Gabon with the location of Combretum rupestre Jongkind & Texier (white circle), also showing the National Parks (hatched areas), main roads and towns, with shading representing elevation by steps of 500 m.

Fig. 4. – Combretum rupestre Jongkind & Texier. A. Flowering branch; B. Detail from leaf from below showing the domatia; C. Part of inflorescence with open flowers; D. Top of inflorescence with flower buds and bracts; E. Flower, side view; F. Flower, top view; G. Flower, length section. [Texier et al. 622, MO] [Drawing: H. de Vries]