Acalypha gillespieae G.A.Levin & I.Montero, 2020

Montero-Munoz, Iris, Levin, Geoffrey A. & Cardiel, Jose M., 2020, Four new species of Acalypha L. (Euphorbiaceae, Acalyphoideae) from the West Indian Ocean Region, PhytoKeys 140, pp. 57-73 : 57

1. Acalypha gillespieae G.A.Levin & I.Montero sp. nov.

Diagnosis.

Acalypha gillespieae G.A.Levin & I.Montero is morphologically most similar to A. humbertii Leandri, but differs from it by having spherical axillary buds with imbricate perules (vs. pyriform buds with superposed perules), elliptic to obovate leaf blades (vs. ovate leaf blades), inflorescences c. 1 cm long with the fertile part of the male segment c. 1.5 mm long (vs. inflorescences c. 2.5 cm long with the male segment c. 20 mm), and mature female bracts subreniform with entire margins (vs. bracts suborbicular with dentate margins).

Type.

Madagascar. Reg. Diana [Prov. Antsirinana]: Montagne des Français, E of Antsirinana (Diego Suarez), 12°19'26.4"S, 49°20'16.6"E, 258 m, 31 Oct 2012, L. J. Gillespie, G. A. Levin, J. Andriatiana, & W. M. Cardinal-McTeague 10692 (holotype: MO!; isotypes: CAN!, K!, P!, TAN!). Fig. 1 .

Description.

Shrubs to 3 m high, intricately branched, deciduous, monoecious. Young branches slender, densely pubescent with short, simple, straight, antrorsely appressed trichomes proximally, and antrorsely curved trichomes distally; older branches glabrescent. Axillary buds spherical, c. 2 mm diam., perules 2, imbricate, chartaceous, glabrous. Stipules deciduous, 2-3.5 mm long, subulate, densely pubescent with short, simple, spreading-ascending trichomes. Petioles slender, 2-5 mm long, densely pubescent with antrorsely curved trichomes. Leaf blades 1.5-4 × 1-3 cm, elliptic to obovate, membranous, unlobed or (2-)3-lobed; base rounded to broadly obtuse; margins crenate; apex obtuse; upper surface sparsely pubescent with simple, straight, erect to antrorse trichomes; lower surface with indumentum similar to that found on upper surface, but denser; venation actinodromous, somewhat prominent on both surfaces, with 3 veins at the base, secondary veins 2-3 per side. Stipels absent. Inflorescences androgynous, axillary, c. 1 cm long, spiciform, with one female bract near the base, and a male segment distally; peduncle thin, 2-3 mm long, densely pubescent with antrorsely curved trichomes; male segment persistent, sterile axis 1-2 mm, fertile portion c. 1.5 mm long, densely pubescent with simple, slender, flexuous trichomes. Female bracts sessile, enlarging in fruit to 5 × 9 mm, subreniform, sparsely pubescent with simple, straight, antrorse trichomes; margins entire. Bracteoles absent. Male flowers not seen (only the pedicels present). Female flowers solitary, sessile; sepals 3, slightly connate at base, c. 0.75 mm long, broadly triangular, ciliate with simple, slender, flexuous trichomes c. 0.5 mm long; ovary not seen; styles 3, persistent in fruit, c. 2 mm long, slightly connate at base, rachis stout, pubescent with short, simple, straight, antrorse trichomes, each style divided into 5-8 slender, fimbriate segments. Capsules 3-locular, c. 3 mm diam., echinate and hispid, with simple, straight, erect to antrorse trichomes c. 0.5 mm long, and conical projections c. 0.75 mm long. Seeds pyriform, 2 × 1.5 mm, smooth.

Distribution and habitat.

Acalypha gillespieae is known only from a small area between 200 and 300 m elevation on the north side of Montagne des Français (Fig. 2 ). This limestone massif, including the area where A. gillespieae grows, is covered with dry deciduous forest ( Moat and Smith 2007, Goodman et al. 2018).

Etymology.

The proposed epithet honors the botanist Lynn J. Gillespie, research scientist at the Canadian Museum of Nature. In addition to studying Arctic plants and Poaceae , she has worked on the systematics of Euphorbiaceae worldwide, including in Madagascar. She collected all the known specimens of this species, either alone or as leader of a team of botanists.

Conservation status.

Acalypha gillespieae is known from three collections from the same locality. Montagne des Français has been relatively well collected (P. Lowry, pers. comm.), so the dearth of collections suggests this species is rare, even there. Its apparent rarity could also, at least in part, reflect it being quite inconspicuous and thus easily overlooked. The extent of occurrence (EOO) could not be calculated. Its area of occupancy (AOO) is estimated to be 8000 km2. Montagne des Français is a category V protected area ( Dudley 2008). Its habitat is somewhat threatened by wood-cutting, primarily for charcoal, but mainly on its lower slopes, below where A. gillespieae is found. Acalypha gillespieae is assigned a preliminary IUCN conservation status of Critically Endangered: CR B2ab(ii,iii,iv).

Additional specimens examined

(paratypes). Madagascar. Reg. Diana [Prov. Antsirinana]: Montagne des Français, E of Antsirinana (Diego Suarez), 12°19'26.4"S, 49°20'16.6"E, 258 m, 31 Oct 2012, L. J. Gillespie, G. A. Levin, J. Andriatiana, & W. M. Cardinal-McTeague 10693 (CAN!, MO!, P!, TAN!); 12°19'S, 49°20'E, 200-300 m, 2 Dec 1990, L. J. Gillespie 4097 (ILLS!, MO!, P[P00324524]!, TAN!).

Notes.

Acalypha gillespieae is very unusual among Acalypha species in having some lobed leaves. The proportion of lobed leaves varies among collections from about 10% in Gillespie et al. 10693 to about 20% in Gillespie et al. 10692 and 70% in Gillespie 4097. The lateral lobes range from much smaller than the central lobe to almost equal to it. The lobes, if present, arise near the base of the blade, with the basal veins becoming the midveins of the lobes. Like the very similar Acalypha humbertii , A. gillespieae flowers when the plants are leafless, probably in late August or September. By the time the leaves emerge in late October, the male flowers have been shed and the female bracts and capsules are mature.

Figures

Figure 1. Acalypha gillespieae A flowering branch with young leaves B flowering branch with mature leaves C detail of node with axillary bud D detail of node, stipules, and petiole base E detail of the androgynous inflorescence F mature female bract G calyx of the female flower H capsule with persistent styles I seed. Based on L. Gillespie 4079 (A, C, E), Gillespie et al. 10693 (B, D), and Gillespie et al. 10692 (F-I). Illustration: Iris Montero Munoz.

Figure 2. Map of Madagascar and the Mayotte island showing the distributions of Acalypha gillespieae (square), A. leandrii (rhombus), A. mayottensis (triangle) and A. nusbaumeri (circle).