Homalium stelliferum subsp. andapense Wassel & Appleq., 2020

Wassel, Anna C. & Applequist, Wendy L., 2020, A revision of Homalium sect. Nisa (Salicaceae) endemic to Madagascar, Candollea 75 (1), pp. 1-23 : 18-20

10b. Homalium stelliferum subsp. andapense Wassel & Appleq. , subsp. nov. ( Fig. 6 ).

Holotypus: MADAGASCAR. Reg. Analanjirofo [Prov. Toamasina]: Maroantsetra , Anjahana-Ambatoledama (à env. 7 km au NW d’Ankovana), massif de Beanjada , 15°16'34"S 49°58'52"E, 1075 m, 26.XI.1997, fl. & fr., Ralimanana & Ranaivojaona 142 ( MO [ MO-6883982 ]!; iso-: G!, K!, P!, TAN) .

Homalium stelliferum subsp. andapense Wassel & Appleq. differs from Homalium stelliferum H. Perrier subsp. stelliferum in having broader and usually larger leaves.

Tree to 30 m tall, 55 cm dbh; bark whitish; twigs with leafing internodes 2–4.2 mm diam. Leaves elliptic to obovate, (5.2–)6.3–14.5 × (2–) 3.1–6.6 cm; apex rounded to cuspidate or emarginate (retuse); margin subentire, sometimes somewhat revolute, to crenulate, with few small glands; drying greenish brown to blackened on adaxial surface, medium brown on abaxial surface; petiole glabrous, 6–13 mm. Inflorescences: bracts and bracteoles sparsely pubescent or glabrous with ciliate margins, (3–) 3.5–4.5 mm. Flowers 6(7)-merous; sepals narrowly oblanceolate-oblong, 9.4 –12 mm in fruit, adaxial and abaxial surfaces glabrous (calyx cup sometimes sparsely pubescent).

Vernacular names. – “Hazombato” (Service Forestier 916); “Longotra” (Ralimanana & Ranaivojaona 142); “Naroankoditra” (Antilahimena 1585).

Distribution, ecology and conservation status. – Homalium stelliferum subsp. andapense has been collected from three northern mid-elevation humid forests. The Extent of Occurrence is calculated as c. 2676 km ² and the Area of Occupancy as 12 km ². The subpopulation from Anjiahely appears to have been within the boundaries of the Makira Natural Park, and the type collection might have been from the peripheral zone of Masoala National Park; the third, more northern locality was collected in 1950 and no recent collections are known from the area. Label data from Ralimanana & Ranaivojaona 142 describes the plant as “rare au bord d’une rivière”. Any accessible habitat outside protected areas in this region would be threatened by human activity such as cutting of trees for wood and fuel. It is unclear what the current range is or whether only a minority, most, or perhaps all of the habitat is within protected areas. It is suggested that the subspecies’ status might therefore best be considered “Data Deficient” [DD].

Notes. – The oldest collection of Homalium stelliferum subsp. andapense was included by SLEUMER (1973) in H. stelliferum without comment. The leaves are larger, at the upper end of their range, than those of H. stelliferum subsp. stelliferum and of different shape, being proportionately broader. There are several other apparent average differences between the two, e.g., H. stelliferum subsp. stelliferum has thinner young twigs, usually more pubescent bracts, bracteoles and calyces, and possibly slightly smaller flowers. However, the consistency of those characters is uncertain. Homalium stelliferum subsp. andapense has a distinct geographic range and perhaps habitat preferences. Because of the limited amount of material of both taxa and the variability seen within H. stelliferum subsp. stelliferum , the new taxon is conservatively treated at subspecific level. Attempts to relocate it and document its range of variation would be highly desirable.

Paratypi. – MADAGASCAR. Reg. Analanjirofo [Prov. Toamasina]: Maroantsetra , Antsirabesahatana , fkt. Anjiahely , 15°25'01"S 49°30'39"E, 420 m, 23.XII.2002, fl., fr., Antilahimena 1585 ( MO, P). Reg. SAVA [Prov. Antsiranana]: vallée de l’Andramonta , W du distr. d’Andapa , 680–700 m, 14.XII.1950, fr., Service Forestier 916 ( P [2 sheets]) .

Figures

Fig. 6. – Holotype of Homalium stelliferum subsp. andapense Wassel & Appleq. [Ralimanana & Ranaivojaona 142, MO] [© Missouri Botanical Garden, Saint Louis]