Homalium brachystylis (Tul.) Baill. in Bull. Mens. Soc. Linn. Paris 1: 573. 1886

Applequist, Wendy L., 2018, A revision of Homalium sect. Odontolobus (Salicaceae) endemic to Madagascar, Candollea 73 (1), pp. 27-48 : 30-31

1. Homalium brachystylis (Tul.) Baill. in Bull. Mens. Soc. Linn. Paris 1: 573. 1886 [as brachystylum].

Ξ Blackwellia brachystylis Tul. in Ann. Sci. Nat., Bot. ser. 4, 8: 59-60. 1857 .

Lectotypus (designated by SLEUMER, 1973: 246): MADAGASCAR. Prov. Antsiranana: Forêts à l’entrée de la Baie de Vohémar , 1837, fl. & fr., Richard 63 ( P [ P04679017 ]! ; isolecto-: G [ G00018411 ] image seen, L [ L0010889 , L0010890 ] images seen) . Syntypi: MADAGASCAR. Prov. Antsiranana: Vohémar, 1846, fl. & fr., Richard 110 [= Boivin 2568] ( P [ P 04734119 ]!). Sine loco: “ Sud de Madagascar [?]”, s.d., fr., Richard 561 ( P [ P 04734120 ]!); Herb. Galldich [cl. Jaubert] 40 (not found) .

= Homalium humbertii H. Perrier in Mém. Mus. Natl. Hist. Nat. 13: 290. 1940 [as humberti]. Lectotypus (first step designated by SLEUMER, 1973: 247; second step designated here): MADAGASCAR. Prov. Toliara: bassin de réception de la Mananara, affluent du Mandrare , pentes occidentales des montagnes entre l’Andohahela et l’Elakelaka , au Vatazo ( S d’Imonty), 900-950 m, II.1934, fl., Humbert 14077 ( P [ P04734112 ]! ; isolecto-: B [ B100153995 ] image seen, G [ G00018412 ] image seen, P [ P04734111 , P04734113 , P04734114 ]!, PRE [ PRE0297345 -0] image seen, TAN [ TAN000242 ] image seen) . Syntypi: MADAGASCAR. Prov. Toliara: vallée moyenne du Mandrare près d’Anadabolava, Mont Vohitrotsy , 700-850 m, XII.1933, fl., Humbert 12655 ( G [ G 00018413 , G 00018414 , G 00018415 ] images seen, P [ P 04734115 , P 04734116 , P 04734117 , P 04734118 ]!, S [ S 10-10143 ] image seen) .

Tree to 12 m tall, 15 cm dbh; bark sometimes described as platanoid; young twigs glabrous or sparsely pubescent, later becoming glabrous. Leaves: petiole (1-)1.5-2.5(-4) mm long, glabrous (sparsely pubescent); blade narrowly elliptical to narrowly oblong-elliptical or elliptical (somewhat obovate), 2.5-7.7 × 0.5-2(-3.4) cm; base convex to cuneate; margins shallowly serrulate to crenulate, usually with few teeth, or subentire; apex acute to rounded (slightly acuminate, obtuse). Inflorescences racemose, 2-7.7 cm long, glabrous or with small patches of pubescence near the point of insertion of flowers (rarely sparsely and minutely pubescent on much of the inflorescence or with small patches of yellowish scaly indument around flowers); flowers solitary, sessile; bracts broadly to transversely ovate, thick-textured; bracteoles transversely to broadly ovate, broadly elliptical, or irregularly transversely oblong, thick-textured. Flowers (5-)6-7(-8)-merous, white to cream-colored, yellow or yellowish green (browning after anthesis); sepals narrowly deltoid to oblong-lanceolate or ligulate, 0.8-1.8 mm long; petals narrowly oblong to narrowly oblong-elliptical or oblong-lanceolate (to somewhat oblanceolate, in north), 1.1-1.8(-2.3) mm long, margins ciliate, otherwise glabrous (adaxial surface rarely pubescent), apex acute (to rounded); filaments 0.3-0.6 mm long; upper surface of ovary moderately villous or pubescent; styles 2(-3), 0.3-0.6 mm long.

Vernacular names. – “Ampolilahy” (Service Forestier 14092); “Mantsapoty” (Service Forestier 9872, 10080); “Somontsohihy” (Be et al. 42); “Tsohontsobe” (Humbert 19161).

Distribution, ecology and conservation status. – Homalium brachystylis is widespread in dry seasonal low to moderateelevation forests and is reported from limestone, sand and silica substrates and in acid soil. It is noteworthy that the single specimen (Andriamihajarivo et al. 293) from the high-elevation quartzite massif [Itremo] near the town of Ambatofinandrahana has much larger leaves than other specimens in the southern part of this species’ range. This massif is an unusual locality that is home to a relatively large number of endemic species, e.g., Andropogon itremoensis Voronts. ( VORONTSOVA et al., 2013) , Buxus itremoensis G.E. Schatz & Lowry (SCHATZ & LOWRY, 2002) , Streptocarpus lanatus MacMaster ( MACMASTER et al., 2005) , Xerochlamys diospyroidea (Baill.) F. Gérard and X. itremoensis Hong-Wa et al. (HONG-WA, 1999). Thus this specimen may be suspected of representing a genetically distinct population that merits further investigation.

The species is widely distributed from the Antsiranana province in the north to the Toliara province in the south and is relatively common with many localities within the protected area network. Homalium brachystylis is therefore assigned a preliminary assessment of conservation status of “Least Concern” [LC].

Notes. – In most of its range, including much of the northern province of Antsiranana, H. brachystylis usually has narrowly elliptical or oblong-elliptical leaves, seldom to elliptical or aberrantly obovate, which are 0.5-2 cm broad (after the exclusion of one large-leaved specimen from Ambatofinandrahana), and has petals that are usually less than 1.8 mm long. A few older collections made in the Vohémar region of northeastern Madagascar have elliptical leaves at maturity, which are 1.9-3.4 cm broad, and unusually large flowers, with petals to 2.3 mm long. They also have relatively narrow bracteoles, short pubescence on the calyx cup, and small patches of indument on the inflorescence rachis above flowers, all features that likewise occur in some narrow-leaved material, though the latter is rare. The protologue of Blackwellia brachystylis indicated that the original material came from the Vohémar region; not all available syntypes are labeled as such (one was later, in another hand and probably erroneously, labeled as “Sud de Madagascar”), but their morphology is consistent with the claim. All original material of Homalium humbertii , which SLEUMER (1973) synonymized with H. brachystylis , is from southern Madagascar and has narrow leaves. The possibility therefore had to be considered that H. brachystylis and H. humbertii should be distinguished from one another at some rank. However, no recent collections from around Vohémar reflect the extreme morphology of the older broadleaved specimens; a couple of recent collections have elliptical leaves and relatively narrow bracteoles, but the flowers are not large, nor is the calyx cup pubescent. Therefore, it appears that there is no clear evidence of a persistent, clearly distinguished taxon endemic to the Vohémar region, and the unusual older specimens represent local genetic variation that does not warrant formal recognition.

The epithet of this species, once transferred to Homalium , is usually given incorrectly as brachystylum. Epithets such as brachystylis should properly be treated as nouns in apposition, which are not declined as adjectives according to the gender of the genus name ( STEARN, 1992: 96-97). Since many authors do treat them as adjectives, the decision to do so is not correctable. However, since the author of the basionym ( Blackwellia brachystylis Tul. ) did choose to use a form correct for a noun in apposition, that choice should be preserved.

SLEUMER (1973) designated Humbert 14077 in the Paris herbarium as the lectotype of Homalium humbertii ; there are in fact four sheets of this collection at P, and he made no selection among them. The International Code of Nomenclature [ICN] ( MCNEILL et al., 2012: Art. 9.17) recommends that a second-stage lectotypification be published to designate a single sheet as the lectotype. The selected sheet is one of the better duplicates, in terms of the size and completeness of the material, and it bears a complete original label.

Selected material examined. – MADAGASCAR. Prov. Antsiranana: env. de RS d’Analamera , 12°40’40’’S 49°32’43’’E, 127 m, 17.I.1995, fl., Andrianantoanina et al. 738 ( BR, G, K, MO, P, WAG) ; massif de l’Ankarana , 12°57’09’’S 49°09’01’’E, 120 m, 26.I.2003, fl. & fr., Bardot-Vaucoulon et al. 1325 ( MO) ; Sahafary, 12°34’30’’S 49°27’32’’E, 200 m, 25.VII.2004, fl., Be et al. 42 ( MO, P) ; Analamera , 50-400 m, I.1938, buds, Humbert 19161 ( P [3 sheets]) ; forêt d’Antsahabe , 10 km à l’W du village d’Ankarafa, 13°12’38’’S 49°33’29’’E, 471 m, 29.X.2005, Rakotondrafara et al. 335 ( MO) ; Sahafary be, 3 km à l’E de Saharenana, 12°35’09’’S 49°27’34’’E, 235 m, 11.IX.2004, fr., Rakotondrajaona et al. 336 ( MO, P) ; Ankarongana, forêt d’Andranomadiro , 12°36’18’’S 49°26’34’’E, 258 m, 7.XI.2006, fl., Ranaivojaona et al. 1519 ( MO) ; Vohemar, forêt de Binara , 13°14’09’’S 49°37’22’’E, 300 m, 31.III.2004, fl., Ranirison 551 ( MO) ; Fkt. Saharenana, forêt d’Andranomadiro , 12°36’18’’S 49°26’35’’E, 300 m, 14.II.2005, fl., Schatz et al. 4264 ( MO) ; Diégo-Suarez , Ankara JB8 , 27.VII.1954, buds, Service Forestier 10426 ( P) ; plateau de l’Ankarana près d’Ambondromifehy , 4-6.X.1954, Service Forestier 11257 ( MO) ; Diégo-Suarez , Ankara , 24.III.1955, fl., Service Forestier 13208 ( P) ; Ankarana à l’W d’Ambondromifehy , 24.IV.1963, fl., Service Forestier 22695 ( MO, P [3 sheets]) ; rebord S du plateau de Mahory, au SW de Marotaolana ( Anivorano-Nord ), 3.IV.1964, fl., Service Forestier 23376 ( P) ; massif de l’Ankitakona , au S de la Baie d’Ambararata, 25-265 m, 25.IV.1966, fl., Service Forestier 24673 ( P) ; massif du Bezavona entre la Fanambana et la Manambery , pentes inférieures de la rive droite de l’Andilana , 20.III.1967, fl., Service Forestier 27537 ( MO, P) . Prov. Fianarantsoa: Ambatofinandrahana, 20°30’03’’S 46°50’51’’E, 1451 m, 20.III.2004, fl., Andriamihajarivo et al. 293 ( MO) ; haute vallée de la Menarahaka a l’E d’Ihosy , 700-800 m, 28.I.1955 & 10.IV.1955, fl., Humbert 28538 ( MO, P) ; between Ankazobetroka and Ambararata , ca. 25 km NE of Ihosy, 22°15’S 46°15’E, 750 m, 11.IV.1971, fl., Mabberley 910 ( P) ; Ihosy, 800 m, VI.1953, fl. & fr., Perrier de la Bâthie 19272 ( P [2 sheets]) ; forêt de Kitranga, à 12 km au N d’Ihosy, I.1955, fl., Service Forestier 11611 ( P [2 sheets]) ; Zasafotsy , Ihosy , 21.VII.1954, buds, Service Forestier 14482 ( P) ; Kitranga , entre Ambararata et Ivandrika , 22.II.1970, fl., Service Forestier 29063 ( P) . Prov. Mahajanga: Bemanevika, forêt d’Analafaly , 17°13’50’’S 46°59’58’’E, 640 m, 9.V.2005, fr., Andrianjafy et al. 1038 ( MO, P) . Prov. Toliara: Andohahela RNI parcelle 2, path E to Ambohibory massif , 24°56’23’’S 46°38’40’’E, 120 m, 9-12.V.1997, fr., Birkinshaw et al. 427 ( MO) ; W du Tsimelahy , Andohahela RNI , 24°56’S 46°35’E, 345 m, 22.III.1995, fl., Eboroke 985 ( G, K, MO) ; forêt de Zombitsy ( Sakaraha ), 600-850 m, 26-29. III.1955, fl. & fr., Humbert et al. 29567 ( P) ; Andohahela, Parcelle 3 , 25°04’S 46°41’E, 100-300 m, 8-10.IV.1993, fr., Randriamampionona 302 ( MO, P) ; RN XI [Andohahela], 18.I.1951, fl., Réserves Naturelles 2756 ( MO, P [2 sheets]) ; Tulear , forêt d’Analavelona , 7.IV.1954, fr., Service Forestier 9872 ( MO, P) ; Mahaboboha, forêt d’Ihera, 9.IV.1954, fr., Service Forestier 10080 ( P) ; forêt de Zombitsy, 700 m, III.1955, fl., Service Forestier 11912 ( P) ; Andranolava , forêt Vohibasia , 27.V.1955, fl., Service Forestier 14092 ( P) ; Forêt de Zombitsy , 700-800 m, 20.VI.1958, fl. & fr., Service Forestier 18593 ( P) .