Homalium vohitsiandrianense Appleq., 2020

Applequist, Wendy L., 2020, A revision of Homalium sect. Rhodonisa (Salicaceae) endemic to Madagascar, Candollea 75 (2), pp. 245-268 : 266

12. Homalium vohitsiandrianense Appleq. , sp. nov.

( Fig. 9 ).

Holotypus: MADAGASCAR. Reg. Anosy [Prov. Toliara]: massif de Vohitsiandriana au N du Cap Andrahomana , 500 m, III.1955, fl., Service Forestier 11837 ( P [ P04679046 ]!).

Homalium vohitsiandrianense Appleq. differs f rom H. rakotovaoi Appleq. in its smaller, often proportionately broader leaves with acute (to rounded or emarginate) apices, shorter racemes, minute but often dense pubescence on pedicels and calyx cups, and very large sepal glands.

Tree to 10 m tall; twigs pale to medium brown, glabrous. Leaves ovate to broadly ovate (aberrantly broadly elliptical), (4–)5–7.8 × (2–) 2.6–4.8 cm, relatively thin-textured; margin irregularly and shallowly crenulate to crenate-denticulate; base convex to rounded; apex acute (rounded, emarginate); both surfaces glabrous, drying pale greenish brown abaxially, mottled dark brown (green adaxially, glossy); secondary veins slightly prominent; petiole 10–16 mm, glabrous. Inflorescences racemose, (1.7–) 3–4 cm; peduncle 0.3–1.3 cm; rachis glabrous; flowers (1–)3–5 per node; pedicels 3–6 mm, minutely but often densely pubescent. Flowers 4-merous; sepals broadly oblong, 1.5 –1.7 mm on type, glabrous or glabrate, margins sparsely short-ciliate; sepal glands broadly elliptical and flattened, 1.2–1.3 × 0.8–0.9 mm; calyx cup minutely but rather densely pubescent; petals obovate, 3.4–4.2 mm on type, accrescence unknown, glabrous, margins not ciliate; filaments 1.8–2.4 mm; anthers broadly elliptical, 0.3 mm high.

Distribution, ecology and conservation status. – Homalium vohitsiandrianense is known only from a single 1955 collection on the southeastern massif of Vohitsiandriana ( Fig. 2 ). The potential habitat will have been substantially reduced in the following 64 years by anthropogenic damage.

If the population still exists, the appropriate assessment of its conservation status is “Critically Endangered” [CR B1ab(iii)+B2ab(iii)].

Notes. – Though H. vohitsiandrianense is known only from the type, it is quite distinct from other species occurring in the region. It is notable for its ovate leaves, racemes with flowers often in clusters of up to 5, long pedicels, broad sepals, and very large sepal glands. The plant is mostly glabrous except for minute, almost long-papillate, but often dense pubescence on the pedicels and calyx cup. It is presumed to be the sister species of H. rakotovaoi , a northern species that shares usually ovate leaves and 4-merous, long-pedicelled flowers often borne in clusters of several. That species has larger, proportionately narrower leaves, longer racemes, and much smaller sepal glands.

Figures

Fig. 9. – Holotype of Homalium vohitsiandrianense Appleq.

Fig. 2. – Map of representative distributions of species in the Homalium albiflorum complex, approximated as necessary.