Pantadenia gervaisii, Rabevohitra & McPHERSON, 2012

Rabevohitra, Raymond & McPHERSON, Gordon, 2012, A new species of Pantadenia Gagnep. (Euphorbiaceae) from Madagascar, Adansonia (3) 34 (1), pp. 77-81 : 78-80

Pantadenia gervaisii

R.Rabev. & McPherson, sp. nov. ( Fig. 1 )

A congeneribus speciebus madagascariensis sylvae orientalis combinatione habitus arborescentis, cum foliis angustis (longitudo> 2 × latitudo) non nisi basi pubescentibus, inflorescentiis parvis glabris, bracteis minutis, calycibus glabris plerumque tetrameris, ovariis bilocularis , et fructibus rotundatis drupaceis distinguenda.

TYPUS. — Madagascar. Prov. Toamasina, Forêt d’Anivoala , au PK 8 de la route de Vatomandry, 9.XII.1980, fleurs ♂, collected by R. Rabevohitra , J. P. Abraham & E. Rakotoarivelo, Service Forestier 32091 (holo-, P! sheet P00461001 ; iso-, TEF!) .

PARATYPI. — Madagascar. Prov. Toamasina, forêt ombrophile d’Anivoala , sur les basses collines de l’est, sur sol sablo-argileux, fr., 20.III.1981, collected by R . Rabevohitra , J . P . Abraham & E . Rakotoarivelo, Service Forestier 32121 ( P!; TEF!). — Forêt d’Anivoala, à 8 km d’Antsampanana , sur la route de Vatomandry, district de Brickaville, fleurs ♀, juv. fr., 9.XII.1982, Service Forestier 32383; Service Forestier 32386 ( P!; TEF!); fleurs ♂, 9.XII.1982, Service Forestier 32388 ( P!; TEF!) .

DESCRIPTION

Dioecious trees up to 10 m tall and 15-20 cm d.b.h. (diameter at breast height); bark smooth, light-coloured; twigs lenticellate, dark on drying. Petioles 10-20(-24) mm long, canaliculate adaxially. Blades ovate, lanceolate, or sometimes elliptic; 5.2-11 cm long, 2.5-5 cm wide; base rounded to shallowly cordate; apex acuminate, often abruptly so, the acumen c. 10-15 mm long; margin entire; veins 3 or 5 from the base, with 2-3 additional pinnately arranged pairs of veins distally, the tertiary venation reticulate and clearly visible on both sides; surfaces glabrous except for hairs in the abaxial axils of the basal veins, the abaxial surface paler than the adaxial on drying, bearing protruding bead-like glands; texture chartaceous. Stipules narrowly triangular, up to 0.5 mm long, apparently sometimes bearing 1-2 glands, caducous. Inflorescences racemiform, appearing terminal and leaf-opposed, glabrous, the staminate 2.5-5 cm long and 10-15 flowered, the pistillate 1.4-3 cm long, 3-6 flowered. Staminate flowers: pedicels 4-6 mm long, glabrous, arising from the primary inflorescence axis via a reduced glabrous segment up to 0.5 mm long; bracts minute; calyx of 4 (or rarely 5) whitish sepals c. 2.5 mm long, c. 2 mm wide, glabrous; corolla of usually 3 petals 1-1.5 mm long, white, each one bearing 3-10 glands marginally, sometimes with a few laminar glands as well; disk interstaminal, of sinuous lobes distributed around and between the outer filaments and resembling a brain coral, the central portion somewhat pubescent; staminodes morphologically intermediate between the petals and the stamens sometimes present; stamens 25-29, the filaments free, c. 1.5 mm long, the anthers curved into a horseshoe-shape, dorsifixed, the connective bearing an apical gland; pistillode absent or perhaps represented by the pubescent central portion of the disk. Pistillate flowers: pedicels 3-6 mm long, glabrous; bracts minute; calyx (persistent in fruit) and corolla as in the staminate flowers; disk annular; ovary bilocular, globose, c. 1.5 mm in diameter, pubescent; stigmas 2, bifid nearly to base, each branch c. 1.5 mm long. Infructescences one- to few-fruited; peduncle 5-7 mm long. Fruit indehiscent, thinly fleshy, 11- 14 mm long, the single-seeded ones subglobose, rounded distally, 10-11 mm in diameter, the double-seeded ones biglobose, slightly notched distally, 15-18 mm wide, glabrous, smooth. Seeds 1 or 2 per fruit, 11-12 m long, c. 10 mm wide, smooth, uniformly brown.

DISTRIBUTION AND ECOLOGY

Pantadenia gervaisii sp. nov. is currently known from one lowland (c. 25 m elevation) rainforest on sandy clay soils in east-central Madagascar (approximately 19°02’S, 48°56’E) .

ETYMOLOGY

The species is dedicated to the late Mr Gervais Andrianirina, Ingénieur de Classe Exceptionnelle des Eaux et Forêts, who worked for 15 years in the Faritany de Toamasina and who was the first author’s Chef de Département, before becoming the Directeur des Services d’Appui à la Recherche at FOFIFA.

CONSERVATION STATUS

Although the new species has been collected only at the type locality, we consider it Endangered ( IUCN 2001), given the extreme fragmentation of its habitat and the ongoing threat of forest clearing.

DISCUSSION

The new species differs most obviously from the other Madagascan species, P. chauvetiae , in its arborescent habit, its narrower leaves pubescent only near the base of the lamina, its glabrous, minutely bracteate inflorescence, its glabrous, typically 4-merous calyx, its more rounded fruits, and in its habitat and distribution (lowland, eastern slope rainforest). Pantadenia chauvetiae , on the other hand, is of smaller stature (3-5 m) and has broader leaves (length> 2 × width) that are pubescent abaxially over most of the surface (although often glabrescent except along the midrib), pubescent and more conspicuously bracteate inflorescences, 5-merous and pubescent calyces, and ovoid fruits. It grows in dry forests near the west-coast city of Morondava.

Both species contrast in ovary locule number and fruit dehiscence with P. adenanthera Gagnep. , the type species, which is native to Southeast Asia. Pantadenia chauvetiae was originally considered ( Capuron 1972) to be unilocular but fruiting specimens collected since its publication demonstrate that the ovary can be bilocular, which is how both Webster (1994) and Radcliffe-Smith (2001) characterize it. Capuron (1972) used the locule number and fruit type of his new taxon as diagnostic characters for the new genus Parapantadenia , contrasting it with the monotypic Southeast Asian Pantadenia , which he considered different only in having a 3-locular ovary and a dehiscent fruit. Radcliffe-Smith (2001) retained the two genera on the same basis, and Pattharahirantricin & Van Welzen (2007) have recently treated Pantadenia as a monotypic genus of mainland Southeast Asia. Webster (1994), however, considered Parapantadenia a synonym of Pantadenia , emphasizing the “peculiar indumentum and inflorescence” that they share, and that position is taken here, as it was by Schatz (2001). Other widely accepted (and distributed) genera in which the number of locules and the fruit type vary as they do in Pantadenia sensu lato include Baccaurea , Croton , Flueggea , Homalanthus , Jatropha , Omphalea and Phyllanthus (Radcliffe- Smith 2001).

Figures

FIG. 1. — Pantadenia gervaisii R.Rabev. & McPherson, sp. nov., Service Forestier 32383: A, flowering branch; B, pistillate flower (one sepal removed).