Homalium ihosyense Appleq., 2020

Applequist, Wendy L., 2020, A revision of Homalium sect. Rhodonisa (Salicaceae) endemic to Madagascar, Candollea 75 (2), pp. 245-268 : 252-254

4. Homalium ihosyense Appleq. , sp. nov. ( Fig. 4 ).

Holotypus: MADAGASCAR. Reg. Ihorombe [Prov. Fianarantsoa]: Vallée de la Menarahaka , à l’E d’Ihosy, II.1955, fl., Service Forestier 11627 ( P [ P04679113 ]!; iso-: P [ P04679040 ]!]).

Homalium ihosyense Appleq. differs from H. analavelonae Appleq. in having thick-textured, usually elliptical leaves, longer racemes with peduncle very reduced, rachis pilose to glabrate, pedicels often longer (0.5–4.5 mm vs. 1–2 mm), and filaments longer (1.3–1.7 mm vs. 0.6–0.8 mm).

Tree to 8 m tall; twigs dark brown when young, becoming gray, glabrous. Leaves elliptical (to somewhat obovate or broadly elliptical), (4.7–)6.7–14 × (3–) 4–6.3 cm, thick-textured; margin inconspiculously crenulate; base convex to rounded; apex cuspidate to short-acuminate (obtuse, rounded); both surfaces glabrous, drying greenish (the upper surface sometimes mottled) to grayish (dark brown); secondary veins slightly prominent; petiole 13–30 mm, glabrous. Inflorescences racemose, (3–) 4.5–11 cm; peduncle virtually absent; rachis moderately pilose to glabrate; flowers 2–3 per node; pedicels 0.5 –4.5 mm, short-pilose. Flowers 5-merous, white; sepals narrowly oblong, 1.8–3 mm, sparsely pilose outside, margins ciliate; sepal glands broadly elliptical, c. 0.6 × 0.5 mm; calyx cup sparsely pilose; petals oblanceolate, 3.5–12 mm, strongly accrescent, sparsely soft-pubescent to sparsely pilose on both surfaces, margins ciliate; filaments 1.3–1.7 mm; anthers broadly elliptical, 0.3 mm high.

Vernacular names. – “Sely” (Service Forestier 13729); “Tratramborondreo” (Service Forestier 13788).

Distribution, ecology and conservation status. – Homalium ihosyense is (or was) endemic to the valley of the Menarahaka near Ihosy ( Fig. 2 ); it was reported to occur in mid-elevation dry forest on sand. The single known population has not been recollected for several decades. The large majority of the native vegetation in this area was unprotected and has been lost since the historical collections were made.

This species is certainly to be assessed as “Critically Endangered” [CR B1ab(iii)+B2ab(iii)], if indeed it is not “Extinct in the wild”.

Notes. – Homalium ihosyense belongs to a group of species including H. albiflorum and H. analavelonae . It is most similar to the latter, which is likewise endemic to a small region of southern Madagascar. Though H. analavelonae is poorly known, it appears to have often broadly elliptical or broadly obovate leaves with usually rounded bases and proportionately shorter petioles; its inflorescence has a short (to 0.6 cm) peduncle, a villous rachis, pedicels to 2 mm long, and long appressed rather than pilose pubescence on the sepals and petals. It may have smaller flowers and smaller sepal glands, but material is too limited to allow conclusions.

Paratypi. – MADAGASCAR. Reg. Ihorombe [Prov. Fianarantsoa]: Haute vallée de la Menarahaka à l’E d’Ihosy, 700–800 m, 28.I & 10.IV.1955, fl., Humbert 28610 ( G, P); ibid. loco, 28.I.1955, fl., Service Forestier 13729 ( P); ibid. loco, 20.III.1955, ster., Service Forestier 13788 ( P); bassin de la Menarahaka , près du carrefour des route d’Ihosy à Ivohibe et Iakora, 650 m, 10.II.1963, fl., Service Forestier 22629 ( G, P [2 sheets]).

Figures

Fig. 4. – Homalium ihosyense Appleq. A. Flowering branch; B. Flower; C. Inflorescence node. [Service Forestier 11627, P] [Drawings: R.L. Andriamiarisoa]

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