Mezoneuron rubiginosum (Guillaumin) R. Clark

Clark, Ruth P., 2016, A Taxonomic Revision of Mezoneuron (Leguminosae: Caesalpinioideae: Caesalpinieae), Phytotaxa 274 (1), pp. 448-450 : 448-450

23. Mezoneuron rubiginosum (Guillaumin) R. Clark in Clark, R. & Gagnon, E. Phytotaxa 207(1): 68–92. 2015.

Lectotype:— NEW CALEDONIA: Boghen, Cribs 982, P (P02969638!); isolectotype: P (P02969637!), Clark & Gagnon 2015. Remaining syntype:— NEW CALEDONIA: Mount Boakim , Lecard s.n., P (P02969633!); isosyntype P (P02969644!). Basionym. Caesalpinia rubiginosa Guillaumin , Bulletin de la Société Botanique de France 83: 309–310. 1936.

Liana to 5 m in length (or more). Stems unarmed; sparsely to moderately whitish to ferruginous tomentose. Stipules semi-persistent, triangular, 1–1.5 × 0.5 mm, sparsely tomentose. Leaves with 4–6 pairs pinnae; 2–5 pairs leaflets per pinna; petiole 4.3–14 cm; rhachis 14.5–25.5 cm, unarmed or with recurved prickles in pairs at pinna insertion points, and sometimes scattered on the internodes; pinnae 4.8–10 cm; leaf rhachis, petiole, and pinna rhachis sparsely to densely whitish or ferruginous tomentose. Leaflets opposite, elliptic to obovate, base oblique, apex rounded to retuse; the terminal leaflets 3.2–5.1 × 2–3.3 cm; lateral leaflets 2.8–5.1 × 1.8–3 cm; 2˚ veins anastomosing, 3˚ veins reticulate, veins clearly visible on both surfaces; all leaflets with upper surface glabrous, or with few whitish to ferruginous hairs on basal midvein, lower surface glabrous or glabrate, with sparse hairs on petiole and midvein, or sparsely appressed hairy, denser on midvein. Inflorescence an axillary, supra-axillary, or terminal, raceme or few to many-branched panicle, congested, the flowers spaced ca. 2–3 mm apart; 12–18.5 cm long, sparsely to densely ferruginous tomentose on peduncle and pedicels; pedicels 2–3 mm, not articulated. Bracts sometimes present, persistent, triangular, ca. 1 × 0.5 mm, moderately to densely tomentose; bracteoles caducous, linear, inrolled, 3 × 0.5–1 mm, moderately to densely ferruginous tomentose. Flowers with a hypanthium ca. 2 mm deep, sparsely to moderately ferruginous tomentose; lower calyx lobe ca. 5 × 2 mm, sparsely ferruginous tomentose, other lobes ca. 4 × 2 mm, glabrous or with very few hairs on the margins. Median petal 6 × 2.5–3 mm, with a patch or band of ferruginous hairs on inner surface of claw, outer surface glabrous. Upper lateral petals elliptic to slightly obovate, 6–7 × 2.5 mm, blade glabrous, claw very sparsely ferruginous tomentose on inner surface or both surfaces very sparsely puberulous. Lower lateral petals elliptic to slightly obovate, 6–7 × 2.5 mm, blade glabrous, claw very sparsely ferruginous tomentose on inner surface or both surfaces very sparsely puberulous. Stamen filaments 6–8 mm long, ferruginous tomentose on the basal ⅓; anthers ca. 1 mm long. Ovary 3–4 mm long, densely ferruginous tomentose, style 4–10 mm long, moderately ferruginous pubescent along most or all of its length; stigma funnel-shaped, the rim papillate. Fruit unknown.

Distribution:—Endemic to New Caledonia. Lifou (Îles Loyauté); Grand Terre, North and South Province, Western side. ( Fig. 26).

40 • Phytotaxa 274 (1) © 2016 Magnolia Press

CLARK

Habitat and ecology:— Wet forest , on non-ultramaphic soil (collections McPherson 2089, Daniker 2390, Hartley 14975). The species may also occur in sclerophyllous forest, according to the localities of some specimens collected in areas that appear to have been formerly vegetated with sclerophyllous forest ( Jaffré et al. 1998). Due to the imprecise nature of the locality information available, however, it is not possible to confidently establish the vegetation type from which some of the specimens were collected (McKee 26003, Cribs 982, Gervais s.n.). Elevation 100–800 m.

Phenology:—Flowering October–November, fruiting time unknown.

Preliminary conservation assessment:—Extent of Occurrence 16,020.691 km ² = VU; Area of Occupancy 16.00 km² = EN.

Category assigned:—Data Deficient (DD). This species has been only occasionally observed due to the difficulty to see it on the top of trees. There is no recent herbarium material. Therefore, M. rubiginosum is assigned as Data Deficient and should be re-assessed when more observations have been made that will clarify its distribution (RLA Flore NC 2016).