Homalium antilahimenae 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 : 4-5

1. Homalium antilahimenae Wassel & Appleq. , sp. nov.

( Fig. 2 ).

Holotypus: MADAGASCAR. Reg. Analanjirofo [Prov. Toamasina]: Fiv. Maroantsetra , comm. Ambinanitelo , fkt. Marovovonana , 15°19'41"S 49°31'29"E, 199 m, 29.VIII.2004, fl., Antilahimena 2621 ( MO [ MO-6755052 ]!; iso-: G!, K!, P!, TAN, USMS) .

Homalium antilahimenae Wassel & Appleq. differs from H. ciliolatum (Sleumer) Wassel & Appleq. in having shorter inflorescences with most flowers borne singly, smaller bracts and bracteoles, and less densely pubescent calyces with indument shorter on cup and sparser towards apical margins of sepals.

Tree 10 to 15 m tall, 60 cm dbh; twigs dark to reddish brown when young, becoming gray to medium brown, glabrous, leafing internodes (0.9–)1.3–2.4(–4) mm diam.; stipules fused, caducous. Leaves elliptic to broadly or narrowly elliptic or obovate, (3.3 –)5– 8(– 10.7) × (1.8–)2– 4.5(–5.4) cm; base cuneate to convex, often short-attenuate at extreme base; apex rounded to cuspidate (acute to slightly acuminate, retuse); margin entire, glands small or absent; secondary veins 7–11 per side; both surfaces glabrous, drying medium-brown on adaxial surface, darker on abaxial surface; petiole glabrous, 4–14 mm. Inflorescences paniculate to racemose, axillary, 2.5–8(–11.8) cm; rachis pubescent, often densely on apical portion; bracts and bracteoles 1–2.5(–3) mm, densely to sparsely short-pubescent throughout or mostly along midrib, often ciliate; flowers usually borne singly, rarely opposite or subopposite. Flowers 6–7(–8)-merous, pale yellow, yellow-green, or whitish; sepals oblanceolate to narrowly oblong-oblanceolate, narrowly elliptic, or in flower obovate to elliptic, 3–6 mm in flower, 5–8 mm in fruit, both surfaces densely to moderately pubescent at base, always densely so on outer surface of calyx cup, short-pubescent on basal portion or along midrib, more sparsely pubescent (to glabrous) towards apical margins; sepal glands glabrous; petals ovate (to broadly ovate when young), 2–3.5 mm in flower, to 5 mm in fruit, both surfaces velutinous; filaments glabrous, (1.2–) 1.9–2.4 mm; anthers 0.4–0.6 mm; styles 1–2 mm.

Etymology. – Homalium antilahimenae is named for botanist Patrice Antilahimena, one of the most experienced living field botanists in Madagascar, who has made over 9500 collections, including the type, and additionally made valuable contributions to ecological and floristic studies (e.g., ANDREWS et al., 1998; PHILLIPSON et al., 2010).

Vernacular names and use. – “Jaborahoditra” (Rakotonirina et al. 180); “Mafaikoditra” (Antilahimena et al. 1213); “Maroampototsa” (Antilahimena 2621); “Tanampotsy” (Service Forestier 15944).

Wood is used to construct houses (Rakotonirina et al. 180).

Distribution, ecology and conservation status. – Homalium antilahimenae is native to the northeastern regions of SAVA and Analanjirofo, where it usually occurs in low- to mid-elevation humid forests (with one specimen labeled at a range of 740–1200 m). It appears to be uncommon. As few as six distinct locations may be known; the Extent of Occurrence (EOO) is calculated as c. 11,190 km ² (which includes a significant area of open water) and the Area of Occupancy (AOO) as 32 km ². Its habitat includes the protected area of Masoala, but other portions of the known habitat are more subject to ongoing anthropogenic degradation. A preliminary assessment of its conservation status is therefore “Vulnerable” [VU B1ab(iii)+2ab(iii)].

Notes. – Homalium antilahimenae is part of a group of three species, including H. ciliolatum (Sleumer) Wassel & Appleq. and H. tenue Wassel & Appleq. , that are separated from H. nudiflorum s.str. by more pubescent flowers and inflorescences. Homalium ciliolatum has often longer inflorescences, 3.5–11.5(–20) cm, larger bracts and bracteoles, 3.5–5(–7) mm long, and sepal indument that covers the entirety of both surfaces, with a markedly longer sericeous indument on the calyx cup. Homalium tenue is distinguished by smaller sepals, 3.5–5(–6) mm in fruit with a glabrous adaxial surface, less pubescent petals, usually smaller leaves, and slender-graceful twigs and rachises.

Paratypi. – MADAGASCAR. Reg. Analanjirofo [Prov. Toamasina]: Maroantsetra , Anjahana , Amodivangy , 15°25'47"S 49°50'07"E, 200 m, 19.VII.2002, fl., Antilahimena et al.1213 ( G, MO) ; Maroantsetra , Ambanizana , NP Masoala , 15°37'48"S 49°59'03"E, 473 m, IX.2002, fl., Antilahimena 2911 ( MO); Anefitrakely private forest , 15°50'04"S 49°40'05"E, 128 m, 28.VII.2007, fl., Antilahimena 5763 ( G, K, MO) ; Ambodimangavolo , Mahasoa , Ambatoharanana , 17°33'57"S 48°53'45"E, 740–1200 m, 25.X.2000, fl., Ratovoson et al. 327 ( G, MO) ; Farankaraina , Maroantsetra , 24.VII.1956, fl., Service Forestier 15944 ( P) ; env. de la Baie d’Antongil , forêt de Fahampanambo , dans la basse vallée de l’Antanambalana , 25–26.IX.1957, fl., Service Forestier 18278 ( P [2 sheets]) . Reg. SAVA [Prov. Antsiranana]: Sambava, Marogaona, Ambodivapaza , 14°08'20"S 49°55' 27"E, 378 m, 27.VIII.2013, Rakotonirina et al. 180 ( MO) .

Figures

Fig. 2. – Holotype of Homalium antilahimenae Wassel & Appleq. [Antilahimena 2621, MO] [© Missouri Botanical Garden, Saint Louis]