Brachiaria comorensis (Mez) A. Camus

Vorontsova, Maria S., 2022, Revision of some Malagasy forage grasses and their relatives within Brachiaria, Echinochloa, Moorochloa, and Urochloa, Candollea 77 (2), pp. 199-236 : 204-207

3. Brachiaria comorensis (Mez) A. Camus in Rev. Int. Bot. Appl. Agric. Trop. 27: 280. 1947 (F ig. 2D, 3).

Panicum comorense Mez in Bot. Jahrb. Syst. 57: 185. 1921.

Lectotypus (designated here): TANZANIA. Reg. Tanga: Usambara, Mlalo, IV.1892, Holst 549 [459] ( B [ B 10 1037908] image!; isolecto-: B [ B 10 1037909] image!, P [ P00450172 ]!, US [ US-80594 fragm.]!) . Syntypus: COMOROS. Grande Comore: sine loco, V.1850, Boivin s.n. ( P [ P00216299 ]!) .

= Brachiaria capuronii A. Camus in Bull. Mus. Natl. Hist. Nat., sér. 2, 29: 278. 1957. Lectotypus (designated here): MADAGASCAR. Reg. Atsimo-Andrefana [Prov. Toliara]: vallée de l’Hazoroa, bassin de l’Onilahy, au S de Sakaraha , 500–600 m, 30.III.1955, Humbert & Capuron 29688 (P [ P00450171 ]!; isolecto-: MO, P [ P03652846 , P03652847 ]!).

= Brachiaria decaryana A. Camus in Bull. Mus. Natl. Hist. Nat., sér. 2, 29: 278. 1957. Lectotypus (designated here): MADAGASCAR. Reg. Sofia [Prov. Mahajanga]: Ankaizinana, 1000 m, 27.IV.1923, Decary 2078 (P [ P00450173 ]!; isolecto-: P [ P00450174 ]!).

Annual to short-lived stoloniferous perennial, ascending, to 0.6 m high, culms weakly branched, rooting at lower nodes, glabrous. Leaf sheath glabrous to sparsely pubescent towards apex. Ligule a truncate membrane with no trichomes. Leaf blade elliptic, membranous, 2.5–15 × 0.5 – 1.3 cm, glaucous underneath, glabrous to sparsely pubescent on both sides. Inflorescence racemose, slender, often incompletely exserted in shade, 5–35 cm long. Racemes 5–20, 2–12 cm long, flexuous, decreasing in length upwards, lowermost raceme roughly equal to inflorescence axis in length, on a common axis 3–20 cm long, often with numerous secondary branches, rhachis narrow, scaberulous, spikelets overlapping untidily with adjacent spikelets, single, pedicels up to twice as long as spikelet. Spikelets elliptic to oblong, apically rounded, 1.5–1.8 mm long, whiteish with a green tinge, sometimes tinged with purple. Lower glume ¼– ⅓ as long as spikelet, membranous, obtuse to acute, 1-veined, glabrous, clasping, orientation relative to rhachis variable. Upper glume as long as spikelet, membranous, 3-veined, veins raised, glabrous. Lower floret infertile, palea absent. Lower lemma membranous, 5-veined, veins raised, depressed between veins. Upper lemma obtuse, smooth, shiny, pale becoming brown at maturity.

Distribution and ecology. – West and eastern tropical Africa and the Comoro Islands. In Madagascar is common in low elevation and sometimes mid-elevation seasonal forest understory and shade, dry and seasonally wet habitats, in the north and south, at elevations of 0–800 m (F ig. 1).

Notes. – Superficially similar to Brachiaria bemarivensis due to shared broad membranous leaf blades and small white apically rounded spikelets, but can be reliably distinguished in a variety of ways: bulbous-based trichomes on leaf surfaces (versus leaf surfaces with linear trichomes in B. bemarivensis), spikelets overlapping (not with gaps between adjacent spikelets within a single raceme), lower glume ¼–⅓ of the spikelet length with a single vein (⅓–½ and with 3 veins), glumes and lower lemma smooth (with enlarged prickle hairs). Often seen sterile or with immature inflorescence emerging from leaf sheaths.

It is not clear why the African floras (HUTCHINSON & DALZIEL, 1972; CLAYTON & RENVOIZE, 1982; CLAYTON, 1989) placed this species in the genus Panicum in spite of its clearly racemose inflorescences while BOSSER (1969) omitted it altogether. Appears to be absent from Mauritius and La Reunion (BOSSER & RENVOIZE, 2018). The first sequence analysis by HACKEL et al. (2018) demonstrated that it is sister to the Malagasy forest endemic Brachiaria tsiafajavonensis A. Camus, see discussion under that species.

The lectotype of Panicum comorense Mez at B [ B 10 1037908] designated here is the best preserved material seen by Mez. The correct collection number seems to be Holst 549, although the second duplicate at B and the fragment at US are labelled as Holst 459 .

Selected specimens examined. – MADAGASCAR. Reg. Alaotra-Mangoro [Prov. Toamasina]: lac Alaotra ( S-169 ) , Jard. Bot. Tananarive 3407 ( P) . Reg. Atsimo-Andrefana [Prov. Toliara]: plateau Mahafaly à l’W de Betioky , III.1955, Humbert & Capuron 29445 ( K, MO, P, TAN) ; PK 32 , rte. pour Ifaty , 21.IV.2014, Nanjarisoa et al. 193 ( K, TAN) ; Beza Mahafaly Reserve , parcelle 1, 13.II.1990, Phillipson 3486 ( K, P) . Reg. Betsiboka [Prov. Mahajanga]: bois F iringalava, III.1898, Perrier de la Bâthie 552 ( P) . Reg. Boeny [Prov. Mahajanga]: Ambato-Boeni, bassin supérieur de Bemarivo , III.1907, Perrier de la Bâthie 11245 ( P) . Reg. Bongolava [Prov. Antananarivo]: Sakay , 1. I.1970, Bosser 20264 ( P) . Reg. AIANA [Prov. Antsiranana]: Daraina , forêt de Bekaraoka, Andranotsimaty, 13.III.2003, Gautier et al. 4359 ( G, P) ; Ambanja, Befalafa, moyen Ambahatra, cours moyen du Bassin-versant , 2. V.1999, Wohlhauser & Andriamalaza 60086[b] ( G, P) ; Ambahatra cours moyen, plateau d’Anketraka Be , 8. V.2000, Wohlhauser 60254 ( G, K, P) . Reg. Ihorombe [Prov. Fianarantsoa]: Parc National Isalo, Canyons des Singes , 25.IV.2018, Rakotomalala et al. 160 ( K, P, TAN) . Reg. Sofia [Prov. Mahajanga]: Bealanana, Ambatoria, Ankaizina, V.1952, Bosser 2661 ( P) .