41. Acalypha rabesahalana I.Montero & Cardiel

Systematic Botany 45 (1): 123 (Montero Muñoz et al. 2020a). —

Type: Madagascar. Diana [Antsiranana], collines et plateaux calcaires de l’Ankarana au Nord (prov. Diego-Suarez), c. 200 m, 12°54’1.27”S, 49°7’58.8”E, H. Humbert 32455 (holo-, P [P05543679]; iso-, P [P00324596], TAN). — Paratypes: Madagascar. Diana region (Antsiranana prov.), collines et plateaux de l’Ankarana du nord (Province de Diego-Suarez), c. 200 m, 12°54’1.27”S, 49°7’58.8”E, 24-29.II.1960, H. Humbert & G. Cours 32480 (G [G00420853], MO, P [P00324454], TAN, WAG [WAG.1810617]).

ICONOGRAPHY. — Montero Muñoz et al. (2020a); Fig. 65E.

ETYMOLOGY. — The epithet honors Gisèle Rabesahala (1929- 2011), Malagasy politician and activist, who was the first woman to hold a ministerial position in the government of Madagascar. She fought for her country’s independence and human rights (Altius & Raveloharimisy 2016).

DISTRIBUTION AND HABITAT. — Endemic to Madagascar (Diana). Dry deciduous forest. On Mesozoic limestone. Altitudinal range 200-350 m (Fig. 62).

PRELIMINARY CONSERVATION ASSESSMENT. — Acalypha rabesahalana is known only from two collections. Its EOO could not be calculated; its AOO is estimated to be 8 km 2. This species appears to be a narrow endemic known only from the Ankarana massif (see assessment of A. ankaranensis). No specimens of this species have been collected for 60 years, so we cannot rule out that this species has become extinct. In recognition of its restricted geographic range (a single known location), the cited threats, and the absence of recent collections, Acalypha rabesahalana is assigned a preliminary conservation status of Critically Endangered: CR B2ab(ii,iii), probably extinct (EX).

MATERIAL EXAMINED. — 2 collections. Madagascar. Humbert, H. 32455 (P[P00324596, P05543679]), 32480 (G[G00420853], MO, P[P00324454], TAN, WAG[WAG.1810617]).

DESCRIPTION

Perennial herbs or rhizomatous subshrubs, to 0.5 m tall, monoecious. Branches puberulent with simple, curved, antrorse trichomes, glabrescent when mature. Axillary buds spherical, to 0.5 mm diameter, perulate, perules 2, valvate, membranous, brownish, puberulent with simple, short, appressed trichomes. Stipules to 3 mm long, narrowly triangular-lanceolate, acute, appressed puberulent, margin ciliate with hyaline trichomes to 1 mm long. Petioles slender, (6-) 7-11 cm long, indumentum similar to that on young branches, and with slender, erect trichomes to 1 mm long. Leaf blades (5-)7-9 × (4-) 6-8 cm, ovate to ovate-lanceolate, membranous; base subcordate; apex acuminate, acumen to 7 mm long, callose-edged; margins crenate-dentate, teeth rounded, callose-edged; upper surface laxly pubescent with some sparse, simple trichomes to 1 mm long, and with simple, minute, curved trichomes on veins; lower surface indumentum similar to that on upper surface but denser, curved trichomes on veins absent; venation actinodromous, basal veins 3 or 5, secondary veins 4-6 per side. Stipels absent. Inflorescences spiciform, unisexual, axillary (male) or subterminal (female). Male inflorescences to 6.5 cm long; peduncle to 20 mm long, it and rachis with indumentum similar to that on young branches; flowers densely glomerate; bracts to 0.5 mm long, triangular, sparsely hairy. Female inflorescences laxly flowered, to 3 cm long; peduncle to 15 mm long, indumentum similar to that on young branches; bracts to 5-10, sessile, enlarging in fruit to 3 × 5 mm, with hyaline trichomes to 1 mm long and simple, short trichomes; margin dentate, teeth 7- 8, to 1/3 bract length, triangular-ovate, central tooth not prominent; bracteoles to 0.4 mm long, lanceolate, sparsely hairy. Male flowers: pedicel to 1 mm long, hispidulous; buds to 1 mm diameter, puberulent. Female flowers 1 per bract, sessile; sepals 3, to 0.5 mm long, triangular-lanceolate, ciliate; ovary c. 0.8 mm diameter, 3-lobed, apparently smooth, surface densely hispid; styles 3, to 4 mm long, connate at base, papillose and hispidulous at base, each divided into 5-6 slender segments. Allomorphic flowers sometimes present at female inflorescence apex; pedicel filiform, to 5 mm long, puberulent with simple, short, curved, antrorse trichomes; sepals 3, similar to those of normal flowers; ovary not seen. Capsules to 2 mm diameter, papillose, papillae obtuse, surface pubescent with simple, short trichomes. Seeds too young to describe.