Prockiopsis grandis G. E. Schatz & Lowry, 2013

Schatz, George E. & Lowry, Porter P., 2013, Two more new species of Prockiopsis Baill. (Achariaceae) from Madagascar, Candollea 68 (2), pp. 277-283 : 279

Prockiopsis grandis G. E. Schatz & Lowry , spec. nova

( Fig. 1-2 ).

Typus: MADAGASCAR. Prov. Antisiranana: Ampasindava, forêt d’Andranomatavy , 13°40’40’’S 47°59’12’’E, 145 m, 25.XI.2009, fl., Ammann, Madiomanana & Tahinarivony 386 (holo-: G [ G00180703 ]! ; iso-: K, MO-6440864 !, P [ P04782036 ]!, TEF) .

Differing from all other species of Prockiopsis by possessing eight (or nine) petals, and having an obovoid fruit that is more than twice as large as that of the two Prockiopsis species for which fruit is known, i.e., P. calcicola and P. hildebrandtii .

Tree to 15 m tall, 18 cm DBH. Stems glabrous. Stipules 4 × 1 mm, linear to narrowly triangular, caducous. Leaves (3.7-) 9.6-14.7 × (2.7-) 2.9-5.9 cm, elliptic to narrowly elliptic, coriaceous, glabrous on both surfaces, base acute to cuneate, margins with 8 to 10 crenulate-serrate teeth, apex acuminate, the acumen to 2 cm, midrib slightly raised above, raised below, glabrous, venation semicraspedodromous, 6 to 9 secondary veins per side, slightly raised on both surfaces, tertiary venation distinctly raised on both surfaces; petioles 2-4 mm, glabrous. Inflorescences axillary, subtended by a pair of narrowly triangular, slightly concave bracts, 2 × 1.5 mm, pseudo-umbellate, 4- or 5-flowered, the peduncle/rachis not visible at anthesis, ca. 1 mm long, ca. 2 mm in diam., the peduncle and rachis elongating post anthesis and into fruit such that the internodes between flowers and their subtending bracts become distinctly visible, the peduncle 4 mm long, 2 mm in diam., the rachis 2.5 mm long. Pedicels subtended by 3 overlapping triangular to ovate-concave, keeled bracts (2 inner and opposite, 1 outer), each 2-2.5 × 1.5 mm, moderately to densely golden tomentose outside, glabrous inside, above which sits a distinct torus of sparse trichomes surrounding the base of the pedicel; pedicels 23-50 mm at anthesis, slender, to 1 mm in diam., crowned by a flange, 1 mm tall, 5 mm in diam., initially with sparse appressed white indumentum, glabrescent by anthesis; pedicels becoming stout in fruit, 1.5 mm in diam. at base, increasing to 2.5 mm at apex. Calyx in bud 9-11 × 4.5 mm in diam., ellipsoid, base truncate, apex acute, entire, calyptriform and tearing irregularly, caducous, thin and tissue-like, with sparse appressed white indumentums outside, glabrous inside. Petals 8 (or 9), of variable size and shape, pale lavender in vivo, the larger ones to 29 × 7-11 mm, spatulate-obovate, sometimes deeply cleft and therefore bilobed, distinctly clawed, the claw 4-5 mm limb, tissue-like with visible venation, glabrous outside, moderately densely beige lanate inside, indumentum persisting towards the rounded apex, the acumen sometimes blunt, the smaller petals to 17 × 4 mm, linear, glabrous outside, moderately densely beige lanate inside, all petals rapidly caducous. Stamens 25 to 30, arranged in two series united into a single ring at their base; filaments 3.5-6.5 mm long, densely white lanate; anthers 4.5-6.0 × 0.5 mm, yellow in vivo. Ovary not seen. Fruit a tardily dehiscent capsule, to 43 mm tall, 32 mm in diam., obovoid, glabrous, smooth “in vivo”, verrucose when dried, crowned by the blunt apiculate stylar remnant, 1- 4 mm; seed not seen.

Notes. – Prockiopsis grandis is known only from two gatherings made ca. 4 km apart from one another at 145 and 310 m elevation on the northern and southern margins of the forêt d’Andranomatavy on the Ampasindava peninsula, which straddles the dry and subhumid bioclimatic zones of CORNET (1974; see SCHATZ, 2000). The forest encompasses an area of isolated hilly topography up to 668 m elevation in the subhumid zone, and is described as «Forêt dense humide sempervirente» on the label of Ammann & al. 489, the gathering from the northern margin of the forest. The remaining forests in the northern part of the Ampasindava peninsula have been classified by HUMBERT (1965) as «Forêt ombrophile du Sambirano», a region with a high level of local endemism to which P. grandis is a further addition. The new species can easily be distinguished from P. hildebrandtii , with which it is sympatric, as well as from the other member of the genus for which fruit is known ( P. calcicola ), by its fruit that is over two times larger than those of P. calcicola and P. hildebrandtii , and by its more numerous petals (8 or sometimes 9 versus 6 in P. calcicola , P. hildebrandtii , and P. orientalis and 4 in P. razakamalalae ), which are also larger (17 to 29 mm long versus 4.5 to 16 mm long in the other four species).

Conservation status. – The forêt d’Andranomatavy encompasses at most 40 km 2 on the Ampasindava peninsula, some of which is fragmented and degraded as a result of human activities. Although a conservation management plan is currently being formulated for the forest, in the absence of effective protection it is unlikely that the forest will persist beyond 3 generations of P. grandis (ca. 45 years). Thus, its risk of extinction can be assessed as “Critically Endangered” (CR A3c) following the IUCN Red List Categories and Criteria ( IUCN, 2012).

Paratypus. – MADAGASCAR. Prov. Antisiranana: Ampasindava, forêt d’Andranomatavy , 13°38’22’’S 47°59’09’’E, 310 m, 15.XII. 2009, fr., Ammann, Madiomanana & Tahinarivony 489 ( G, K, MO, P, TEF, WAG) .

Figures

Fig. 1. – Holotype of Prockiopsis grandis G. E. Schatz & Lowry. [Ammann, Madiomanana & Tahinarivony 386, G]

Fig. 2. – Flower of Prockiopsis grandis G. E. Schatz & Lowry. [Photo: M. Y. Ammann]