Homalium louvelianum H. Perrier

Wassel, Anna C. & Applequist, Wendy L., 2020, A revision of Homalium sect. Nisa (Salicaceae) endemic to Madagascar, Candollea 75 (1), pp. 1-23 : 9-10

5. Homalium louvelianum H. Perrier in Mém. Mus. Natl. Hist. Nat. 13: 292. 1940.

Lectotypus (designated by SLEUMER, 1973: 296): MADAGASCAR. Reg. Atsinanana [Prov. Toamasina]: Tampina, s.d., fl. & fr., Louvel 87 ( P [ P04704068 ]!) . Syntypi: MADAGASCAR. Reg. Atsinanana [Prov. Toamasina]: Ambila au S de Tamatave , 4.V.1928, fl., Decary 6381 ( P [ P04704069 ]!, PRE [ PRE0602227 -0] image seen, S [ S10-10168 ] image seen, US [ US00603578 ] image seen) ; forêts côtières [ Tampina ?], s.d., fl., Louvel 109 ( P [ P04704067 ]!) . Reg. Vatovavy-Fitovinany [Prov. F ianarantsoa]: Mananjary, zone côtière, III–IV.1909, fl., Geay 7425 ( P [ P04704065 ]!) ; ibid. loco, fl., Geay 7426 ( P [ P04704066 ]!) ; ibid. loco, fl., Geay 8069 ( P [ P04704064 ]!) .

Tree to 16 m tall, 40 cm dbh; bark orange or yellowish, exfoliating in plaques; twigs reddish brown when young, becoming grayish brown, glaucous to glabrous (minutely papillate), leafing internodes 1–2.5(–4.2) mm diam.; stipules fused, caducous. Leaves narrowly elliptical to oblanceolate or elliptical (obovate), (3.5–)5.5–12(–14) × (1.5–)2–3.9(–4.5) cm; base cuneate to narrowly convex (slightly attenuate); apex acute to rounded, sometimes partly rounded-cuspidate, short-acuminate, or retuse; margin subentire, usually somewhat revolute at least at base, with glands in inconspicuous concavities or projections; secondary veins (6–)8–12(–14) per side, sometimes with very similar intersecondary veins; both surfaces glabrous, drying brown to dark (or greenish) brown on adaxial surface, usually somewhat paler brown on abaxial surface; petiole glabrous, (2 –)3– 11(– 15) mm. Inflorescences racemose, axillary, 0.7–3.7(–5.6) cm; rachis glabrous; bracts and bracteoles glabrous except for sometimes ciliate margins, 0.5 – 1.5 mm; flowers borne singly (but usually clustered close together) or paired. Flowers 5– 6-merous (aberrantly 4-merous), pale yellow to pale green or green sometimes with pinkish margins, or abaxial surface of calyx reddish; sepals broadly oblong-ovate (to ovate-deltoid), (1 –) 1.2 – 1.8 mm in flower, (1–)1.5–2.6(– 3.5) mm in fruit, adaxial and abaxial surfaces glabrous (calyx cup seldom sparsely pubescent); sepal glands yellow, glabrous; petals oblong-elliptic (broadly oblongovate), not curving inwards in fruit, 1.3 –1.8 mm in flower, (1 –)1.5–2(–2.5) mm in fruit, abaxial surface densely shortpubescent (to glabrous at margins toward base), adaxial surface densely to moderately short-pubescent towards apex, ciliate on most of margin; filaments glabrous, (0.8–)0.9–1.2(–1.3) mm; anthers 0.3–0.4(–0.45) mm; styles (0.4–)0.5–0.5(–1) mm.

Vernacular names and use. – “Fotsiakara” (Ludovic & Ratiana 666, Ludovic 703, 735, Service Forestier 15375); “Fotsiakarjay fotsy” (Ludovic 391), “Gavoala” (Service Forestier 1562, 4702, 5690, 9531, 16869, 19188, 19502 [Betsimaraka dialect]); “Goaviala” (Service Forestier 4916); “Goviala” (Louvel 87, 109); “Hafeala” (Service Forestier 2936); “Hazombato” (Birkinshaw et al. 355, Rabevohitra et al. 4985, Randrianaivo et al. 1875); “Hazombatovavy” (Service Forestier 14837); “Langipasina” (Service Forestier 9514); “Ramirisa” (Service Forestier 2851, 3361); “Ramirisy” (Service Forestier 6975 [Tanosy dialect]); “Rotra” (Cours 2952); “Zahandambo” (Service Forestier 2110).

Wood is used for construction (Ludovic & Ratiana 666, Ludovic 703, Service Forestier 19188, 19502).

Distribution, ecology and conservation status. – Homalium louvelianum is widely distributed along most of the eastern coast of Madagascar. It is found in littoral forests, or less often low-altitude humid forests near the coast, on sand and ferralitic soil. Although littoral forests are highly fragmented and threatened, H. louvelianum is still frequently collected over a wide range. Its conservation status is assessed as “Least Concern” [LC].

Notes. – Homalium louvelianum displays less perianth accrescence than any other species of Homalium sect. Nisa . It has the smallest flowers within the section, and is unique in having sepals similar in size to the petals and broadest towards the base. The flowers often appear crowded on short racemes, though occasionally the rachis is relatively elongated and flowers more widely spaced. In these characters and the unusually short styles and filaments, the species bears a strong resemblance to those species of Homalium sect. Odontolobus Warb. s.l. ( APPLEQUIST, 2018a) that display less extreme floral reduction. While no molecular data adequate to resolve relationships within Malagasy Homalium are available, this species suggests an intermediate or transitional form between those two sections which may provide a clue as to their relationships.

Razakamalala et al. 3796 is identified as a hybrid between H. louvelianum and H. tenue . The leaves are consistent with H. louvelianum , narrowly elliptical with acute to acuminate apices. The sepals are only slightly longer than the petals, but resemble those of most species of Homalium sect. Nisa in shape and texture and are slightly reflexed, while the petals are densely pubescent and slightly inward-curving. Homalium tenue is found at this locality and its leaf shape and dense petal indument make it the presumptive second parent.

Three specimens are from farther north than any population of typical Homalium louvelianum and occur at unusually high altitudes. Birkinshaw et al. 2015 has large, unusually shaped leaves and pubescent inflorescences and sepals. Two others from the forest of Ampondrabe have small leaves; their floral morphology is largely consistent with H. louvelianum . If typical H. louvelianum occurred in these regions, these specimens would be presumed to be hybrids, but since they are far from the known range of H. louvelianum , it is possible that they represent distinct species for which material is insufficient to allow recognition. Further investigation of these populations would be desirable.

Additional material examined. – MADAGASCAR. Reg. Analanjirofo [Prov. Toamasina]: 1 km S Mandrisy along road, 16°29'02"S 49°50'45"E, 10 m, 9.VII.1996, fr., Birkinshaw et al. 355 ( MO, P) ; Ile Sainte-Marie, forêt d’Ambohidena , 16°51'11"S 49°57'10"E, 10 m, 13. V.2003, fr., McPherson et al. 18894 ( MO, P) ; Soanierana-Ivongo, Antanambao-Ambodimanga , 16°46'19"S 49°43'52"E, 18.V.2003, fr., Rabenantoandro et al. 1481 ( MO, P) ; fkt. Ambohidena, forêt d’Ambohidena , 16°51'11"S 49°57'18"E, 18.II.2004, fl., Rabevohitra et al. 4985 ( MO, P) ; fkt. Manompana, forêt de Pointalare [Pointe à Larrée], 16°47'18"S 49°41'08"E, 24 m, 14. VI.2011, fr., Randrianaivo et al. 1875 ( P) ; Tampolo , 17°17'S 49°25'E, 0–5 m, 5–15.V.1997, fl., Ravololonanahary et al. 82 ( MO, P) ; fkt. Ambohidena, forêt d’Ambohidena , 16°50'25"S 49°57'09"E, 10 m, 19.II.2004, fl., Razakamalala et al. 899 ( MO, P) ; Mahambo, au S de Fénérive , 30.VIII.1957, fr., Service Forestier 18143 ( P [2 sheets]) ; S de la Mandrisy, S d’Antanambe, Mananara , 13.XI.1964, fr., Service Forestier 23771 ( P [2 sheets]) . Reg. Anosy [Prov. Toliara]: Mandena , 24°57' S 47°00'E, 0–10 m, 19.IV.1989, fl., Gereau et al. 3388 ( MO, P) ; Ste. Luce , 24°47'S 47°10'E, 20 m, 15. I.1990, fl., McPherson et al. 14796 ( MO, P) ; Ft-Dauphin , fkt. Tsiharoa, forêt d’Etazo ( S 5 ) , 24°49'36"S 47°06'44"E, 20 m, 8.VIII.2012, Rakotonirina et al. 870 ( MO) ; Mandena , 24°57'S 47°00'E, 0 m, 22.VI.1996, fr., Razafimandimbison 211 ( G, K, MO, P) ; Mandena, Ft-Dauphin, 7.III.1951, fl., Service Forestier 2851 ( P) ; Mandena, 11 km au N de Ft. Dauphin , IV–V.1953, fl., Service Forestier 6975 ( P) . Reg. Atsimo-Atsinanana [Prov. Fianarantsoa]: fkt. Baboaka , 1.5 km SW d’Analamena, 23°09'37"S 47°44'41"E, 15 m, 6.VI.2003, fr., Ludovic 391 ( MO) ; Vohimasy, Agnalazaha Ampoakafo , 23°10'58"S, 47°42'27"E, 12 m, 13.VIII.2006, fr., Razafitsalama 961 ( MO) ; Mahabo Mananivo, forêt de Manombo , 23°10'12"S 47°42'50"E, 21 m, fl., Razakamalala & Rabehevitra 701 ( MO [2 sheets], P) ; Manombo RS, parcelle I, forêt d’Anaviavy , 22°59'16"S 47°42'26"E, 65 m, 14.IX.2005, fl., Razakamalala et al. 2127 ( P) ; Analazaka, Efotsy, 30.VIII.1955, fl., Service Forestier 15375 ( P) ; Vohimasy, Agnalazaha Ampoakafo , 23°10'58"S 47°42'27"E, 12 m, 13.VIII.2006, fr., Razafitsalama 961 ( MO) . Reg. Atsinanana [Prov. Toamasina]: Ambila-Lemaitso , 18°49'28"S 49°09'19"E, 10 m, 25.IX.2000, fl., Andrianjafy et al. 108 ( MO, P) ; Vohibola , N of Lac Ampitabe, 18°33'34"S 49°15'01"E, 5 m, 12.II.2003, fr., Lowry et al. 6074 ( MO, P) ; fkt. Andranonkoditra, forêt de Vohibola , 18°35'32"S 49°14'02"E, 5 m, 11.II.2003, fr., Rabenantoandro et al. 1259 ( MO, P) ; Akanin’ny Nofy, forêt de Vohibola , 18°33'46"S 49°15'06"E, 3.VIII.2003, fr., Razakamalala & Rabehevitra 649 ( MO, P) ; Ambila-Lemaitso, 25.X.1950, fr., Service Forestier 1562 ( P) ; Ambila-Lemaitso, 14.IV.1952, fr., Service Forestier 4702 ( MO, P) ; ibid. loco, 25.IX.1952, fr., Service Forestier 5690 ( P) ; ibid. loco, 16.III.1954, fr., Service Forestier 9531 ( P) ; Tampina, JB 20, 12.IX. 1958, fr., Service Forestier 19188 ( P) ; Ambila-Lemaitso, Jardin Botanique no. 2, 22.V.1959, fl., Service Forestier 19502 ( P) . Reg. Vatovavy-Fitovinany [Prov. Fianarantsoa]: fkt. Marohita, forêt d’Ambahisosotra , 21°29'12"S 48°16'20"E, 13 m, fr., Ranaivojaona et al. 541 ( MO, P) ; fkt. Ambalavontaka, forêt d’Antaimby , 20°23'26"S 48°32' 43"E, 10 m, 20.IV.2004, fr., Ranaivojaona et al. 651 ( MO, P) ; Pangalane, sud[?] Mananjary, 24.2.1954, fl., Service Forestier 9514 ( P) ; forêt de Manampano, Mananjary, 17.VI.1955, fr., Service Forestier 14837 ( P) . Sine loco: 3–5 m, 10.X.1946, fr., Cours 2952 ( MO, P) .

Hybrid specimen. – MADAGASCAR. Reg. Anosy [Prov. Toliara]: Iaboko, Antsotso Avaratra , 24°34'16"S 47°12'06"E, 271 m, 8.XII.2007, fr., Razakamalala et al. 3796 ( P) .

Specimens incertae sedis. – MADAGASCAR. Reg. SAVA [Prov. Antsiranana]: Tsihomanaomby access from Antanambaonisokitra , 14°05'52"S 50°00'26"E, 331 m, 23.IV.2014, fl., Birkinshaw et al. 2015 ( MO); Daraina , forêt d’Ampondrabe , 12°57'14"S, 49°42'13"E, 517 m, 9.IV.2004, fl., Ranirison 612 ( P); Tsaratanana , Ambarilao , forêt d’Ampondrabe ( Antsanjoana ), 12°57'29"S 49°41'32"E, 600 m, 9.XI.2005, fr., Ratovoson et al. 1094 ( MO, P) .