Acalypha humbertii Leandri

Muñoz, Iris Montero, Levin, Geoffrey A. & Cardiel, José María, 2023, Monograph of Acalypha L. (Euphorbiaceae) of the Western Indian Ocean Region, with the description of a new species from Mayotte, Adansonia (3) 45 (26), pp. 395-496 : 441-443

20. Acalypha humbertii Leandri

Notulae Systematicae. Herbier du Muséum de Paris. Phanérogramie. Paris 10: 274 ( Leandri 1942). — Type: Madagascar. Prov. Toliara, vallées du Mangoky et de l’Isahaina, aux environs de Beroroha, 200 m, X.1933, H. Humbert 11289 (lecto-, designated byMontero Muñoz et al. [2018a: 99]: P[P00508400]; isolecto-, P[P00508399]). — Former syntypes: Madagascar. Prov. Toliara, Bassin supérieur de Mandrare du Sud-Est, entre le col de Vavara et la vallée de la Manambolo, 700-1200 m, 20-22.XII.1928, H. Humbert 6758 (P[P00508401, P00508402, P00508403, P00508404]).

ICONOGRAPHY. — Fig. 35G.

ETYMOLOGY. — The epithet honors French botanist Henri [JeanHenri] Humbert (1887-1967).

DISTRIBUTION AND HABITAT. — Endemic to Madagascar (Menabe, Atsimo-Andrefana, Androy, and Anosy). Dry deciduous forest and dry spiny thickets. On basement rocks and sandstone. Altitudinal range (50-) 200-800 (-1000) m ( Fig. 36 ).

PRELIMINARY CONSERVATION ASSESSMENT. — The EOO of Acalypha humbertii is estimated to be 37 244 km 2 and its AOO 20 km 2, which is less than the 500 km 2 threshold of the B2 subcriterion of the Endangered category. This species grows mainly in dry deciduous forest and spiny thickets (see assessment in A. decaryana ). The remaining original vegetation is still decreasing. Due to its small AOO, the small number of locations (5), and ongoing habitat loss, Acalypha humbertii is assessed as Endangered: EN B2ab(ii,iii,iv).

MATERIAL EXAMINED. — 11 collections. Madagascar: Bosser, M.J. 10234 (P[P00324559]); Decary, R. 15637 (P[P00324536, P05510104]); Humbert , H. 6758 (P[P00508401, P00508402, P00508403, P00508404]), 11289 (P[P00508399, P00508400]); Jongkind, C.C.H. 3708 ( MO, TAN, WAG[WAG.1578689]); Kaudern, W. 222 (S[S17-37631]), 289 (S[S17-37632]); Leandri, J. 3532 (P[P00324507, P05543682]), 3535 (P[P05547075]), 3882 (P[P00324510]), 3900 (P[P00324511, P05543681]).

REFERENCES. — Govaerts et al. (2000: 67); Montero Muñoz et al. (2018a: 99).

DESCRIPTION

Shrubs, deciduous, to 1.5 m tall, highly divaricately branched, monoecious. Branches densely pubescent to subvelutinous, glabrescent when mature. Axillary buds subfusiform, to 4 × 2 mm, perulate, perules 2, imbricate, chartaceous, dark brown, glabrous. Stipules to 3 mm long, linear, densely pubescent. Petioles 0.5-1.5 long, indumentum similar to that on young branches. Leaf blades 2.4-3.7 × 1.4-2.6 cm, ovate-lanceolate to elliptic-lanceolate, subchartaceous; base rounded to subacute; apex rounded to subacuminate, acumen to 2 mm long, rounded; margin crenate-serrate, teeth rounded, callose-edged; upper and lower surfaces velutinous with simple, short trichomes; venation actinodromous, basal veins 3, secondary veins 4-5 per side. Stipels absent. Inflorescences spiciform, androgynous, axillary, to 3 cm long, mostly male with 1 female bract at base; peduncle to 5 mm long, it and rachis pubescent with simple, short trichomes. Female segment: bract 1, sessile, enlarging in fruit to 6 × 8 mm, reniform, pubescent with simple, short trichomes; margin subentire to irregularly dentate, teeth c. 13, triangular, central tooth not prominent; bracteoles to 0.8 mm long, oblong-lanceolate, sparsely hairy. Male segment persistent, to 1.8 cm long; flowers glomerate; bracts to 0.5 mm long, triangular, sparsely hairy. Male flowers: pedicel to 0.6 mm long, sparsely hairy; buds not seen. Female flowers 1 per bract, sessile; sepals 3, to 0.7 mm long, ovate-lanceolate, ciliate; ovary c. 1 mm diameter, 3-lobed, echinate, projections linear, to 1.5 mm long, surface hispid with simple, rigid trichomes; styles 3, to 3.5 mm long, connate at base, sparsely hairy with simple, long, appressed trichomes at rachis, each divided into c. 8 segments. Allomorphic flowers not seen. Capsules to 2.5 mm diameter, echinate, projections linear, to 1.5 mm long, surface hispid with simple, rigid trichomes. Seeds c. 1.5 × 1.2 mm, pyriform, minutely foveolate.

Figures

FIG. 35. — Mature female bracts: A, Acalypha decaryana Leandri (R. Decary 2985); B, A. emirnensis Baill. (G. McPherson 14590); C, A. filiformis Poir. (P. Commerson s.n.); D, A. fimbriata Schumach. & Thonn. (J. Audru 40466); E, A. gillespieae G.A.Levin & I.Montero (L. Gillespie et al. 10692); F, A. gracilipes Baill. (R. Rabevohitra 2054); G, A. humbertii Leandri (W. Kaudern 222). Illustration by Iris Montero Muñoz. Scale bars: A, C-G, 1 mm; B, 2 mm.

FIG. 36. — Distribution map of Acalypha humbertii Leandri in Madagascar.