Polyosma kouaouana Pillon, 2018

Pillon, Yohan, 2018, Nomenclature and typification in Polyosma (Escalloniaceae) from New Caledonia, with the description of a new species, Phytotaxa 371 (4), pp. 267-272 : 269-270

Polyosma kouaouana Pillon , sp. nov ( Figure 1 )

A species most similar to Polyosma spicata in the size, shape and glaucous aspect of its leaves, and to Polyosma discolor in its near sessile fruits, but which differs from both by the leaf margin that is minutely toothed or sinuate and the leaf blade that is bullate.

Type: — NEW CALEDONIA. Kouaoua , Aréha, 500 m, 30 march 1982, McKee (leg. J.- F. Cherrier) 40295 (holotype P-04377521!) .

Shrub 2–6 m tall, glabrous except on bud, with lenticels on younger wood. Leaves: pseudo-opposite, elliptic with rounded to pointed apex, base triangular, petiole 16–45 × 1–2 mm, blade coriaceous, bullate, 4.5–14 × 2–4.8 cm, lower surface glaucous below, margins with fine teeth (<1 mm long) or sinuses; 6–13 pairs of secondary veins, convex below, concave above. Young inflorescences with very short shiny hairs, 3.5–7.5 cm long, bracts 2 × 0.2 mm. Flowers: pedicel c. 1 mm long; calyx tube c. 1.5 mm long with 4 spreading tips; corolla 2.5–3 mm long in bud; buds pinkish (fide McKee 9902), purple ( H. Vandrot, pers. comm.) or reddish green (Barrabé 934). Flower at anthesis unkown. Fruits ovoid, 8 × 6 mm, glabrous, smooth, with 2 longitudinal furrows, pyrenes 2 per fruit, 7 × 4 mm. Seeds ellipsoid, 4 × 2 mm.

Ecology and conservation: —Unlike the morphologically similar P. spicata and P. discolor , this species occurs on ultramafic substrates in maquis and mountain forest, at 500–1000 m elevation. It is known so far from only 4 localities: Kouaoua (Aréha, Montmartre), Mé Maoya (ridge between Baraoua and Houailou rivers), Boulinda (pic Poya), and Paéoua (H. Vandrot, pers. comm.). They are all located within a 40 km radius. This patchy distribution is quite similar to that of Pancheria ajiearoana H.C.Hopkin, Pillon & Bradford (2009: 442) . All populations may be directly affected by nickel mining, particularly the first one. This species will be assessed by the New Caledonia Plant Red List Authority and would likely qualify as Endangered EN B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v) ( IUCN 2017).

Paratypes: — New Caledonia, Kouaoua : décharge Montmartre, 14 february 1978, Veillon 3504 ( P!) ; Kouaoua , Mine de Méa, décharge Montmartre, 165°45’52’’E, 21°26’29’’S, 723 m, 17 august 2009, Barrabé & Nigote 934 ( P!, K, NOU, NY, Z, S) ; Mt Boulinda , près du Pic Poya, 800 m, 7 november 1984, Veillon 5830 ( P!) ; Crête entre la haute Houailou et la haute Baraoua (contrefort du Mé Maoya), 28 december 1962, McKee 9902 ( P!) .

Notes: —the collection McPherson 2933 (P-04362121!) from Mount Mé Maoya is tentatively assigned to this species. It differs by its leaves that are more strongly toothed and more chartaceous. It could be juvenile foliage although this collection is fertile. The collections from the West (Boulinda & Mé Maoya) look somewhat different from those from the type locality (Kouaoua), with leaves that are smaller, not so strongly bullate and the margin that is sinuate rather than toothed in Veillon 5830. Further observations are needed before deciding whether this taxon should be further divided.

Figures

FIGURE 1. Polyosma kouaouana Pillon. A. Branch with fruits; B. Sinuate leaf margin; C. Toothed leaf margin; D. Fruit and two pyrenes; E. Transversal section of a pyrene and a seed. A, C–E: McKee (leg. J.-F. Cherrier) 40295; B: Veillon 5830. Scale bars: A: 1 cm, B–E: 2 mm.