Labramia ambondrombeensis L. Gaut. & Randriarisoa, 2020

Randriarisoa, Aina, Naciri, Yamama & Gautier, Laurent, 2020, Labramia ambondrombeensis (Sapotaceae), a Critically Endangered new species from Madagascar., Candollea 75 (1), pp. 83-87 : 84-86

Labramia ambondrombeensis L. Gaut. & Randriarisoa , sp. nov.

( Fig. 1 ).

Holotypus: MADAGAsCAR. R e g. S AVA [Pr o v. Antsiranana]: Fiv. Vohemara , Fkt. Manakana , à l’E du village à Ambondrobe , 13°43'08"S 50°05'50"E, 13.III.2004, fl., Razakamalala, Rabevohitra & Faralahy 1077 ( G [ G00105531 ]!; iso-: MO-1979356 !, P [ P04568848 ]!, TEF!) .

Labramia ambondrombeensis L. Gaut. & Randriarisoa is similar to L. platanoides Capuron ex Aubrév. in having relatively small leaves for the genus but differs by its cuneiform leaf blade (vs. obovate), by its longer flower pedicels (12–15 vs. 6–7 mm) and its 9–10 celled ovary (vs. 6 (–7) celled).

Tree (dimensions unknown), with white latex. Ultimate twigs 2 mm diameter, glabrous, brownish, with pales lenticels, soon becoming greyish and longitudinally ridged. Leaves alternate, petiole 10–15 × 1.1–1.6 mm, glabrous, with a median groove on upper side in continuation of the primary nerve; blade cuneiform, the widest portion 1/4 from the top and decreasing almost regularly to the acute base, apex rounded to slightly emarginated; (30–)40–65(–70) × 15–30 mm, entirely glabrous even when young, drying brown and discolours, darker above. Primary nerve prominent below, depressed above; secondary venation inconspicuous on upper side, visible on lower side, 10–12 pairs of secondaries, ascending with an angle of c. 30°–40°, straight and parallel to each other until their connexion through a marginal nerve 0.9 mm from the margin; intersecondaries present; tertiary venation faint. Flowers 1–3, fasciculate, borne axillary to the current year’s leaves or above the scar of previous year’s fallen leaves; flowering pedicels 12– 15 × 0.6–0.8 mm, broadening to c. 1.2 mm in their upper third, entirely glabrous. Sepals 6, arranged in two valvate whorls; the three outer ones ovate, 4.5 × 2.0 mm, apex acute, base rounded, entirely glabrous, the three inner ones lanceolate, 4.5 × 1.5 mm, apex acute, base rounded, thinly puberulent on outer side, inner side glabrous. Corolla gamopetalous glabrous, tube 2.2 mm long, with a spherical lower part 1.2 mm long and 1.4 mm in diameter surrounding the ovary, then constricted to 1.0 mm in diameter, the upper part thicker and broadening up to the mouth, with 6 lanceolate lobes, 3.4 × 1.0 mm, apparently erect at anthesis, each with a pair of lateral appendages deeply incised in linear filaments up to 2.7 mm long. Stamens 6, filaments 0.4 mm broad at base, tapering to 0.2 mm at top, 0.8 mm long, attached to the top of the corolla tube. Anther pairs narrowly sagittate, medifixed, extrorse, 2.2 × 0.8 mm at the broadest, concealed in the corolla lobes. Staminodes absent or if present then 6, vestigial, alternate with respect to petals and stamens, triangular, 0.5 × 0.5 mm, glabrous. Ovary broadly conical, 2.2 mm high × 1.2 mm in diam., glabrous, 9–10 celled with 1 ovule per cell, style narrowly conical 4 mm long, 1.3 mm diam. at base, 0.4 mm below stigma, glabrous. Fruit unknown.

Etymology. – This species epithet refers to the name of the village of Ambondrombe, near the littoral forest where the type specimen was collected.

Phenology. – The flowering specimen was collected in March.

Distribution and Ecology. – Labramia ambondrombeensis is only known from the type collection in Northeastern Madagascar, at the extreme North of the Eastern Phytogeographic Domain, near the southern limit of the Northern Sector of the Western Domain ( HUMBERT, 1955). It was collected in a littoral forest on sands.

Conservation status. – The new species is known only from a single location in a little patch of unprotected littoral forest. Littoral forest is under major threat of logging and habitat conversion ( CONSIGLIO et al., 2006). With only one known location and an AOO of 4 km ², outside of the protected area network, L. ambondrombeensis is assigned a provisional status of “Critically Endangered” [CR B1ab(i,ii,iii)+2ab(i,ii,iii)] using the IUCN Red List Criteria ( IUCN, 2012).

Notes. – Labramia ambondrombeensis is clearly distinct from most other Labramia species because of its small leaves (4.0– 6.5 cm long). The only other species, also occurring in the North of Madagascar, with such small leaves is L. platanoides Capuron ex Aubrév. Apart from the morphological distinctions, habitat preferences distinguish the two species: while the specimen of Labramia ambondrombeensis was collected in littoral forest on sand, Labramia platanoides is known to have a predilection for dry deciduous to semi-deciduous forests on limestone ( AUBRÉVILLE, 1974). Labramia ambondrombeensis is not the only species in littoral forest; further south, under per-humid climate, one finds L. bojeri with much larger leaves (up to 25 cm long).

Figures

Fig. 1. – Labramia ambondrombeensis L. Gaut. & Randriarisoa. A. Flowering branch; B. Leaf with venation details (a: upper side; b: lower side); C. Flower; D. Flower in longitudinal section; E. Detached corolla spread opened (c: outer side, with appendages folded down and one lobe removed to show one lobe and one stamen; d: inner side, with two stamens removed to show inner side of lobes); F. Transversal section of the ovary. [Razakamalala et al. 1077, G] [Drawing: G. Loza]