Brachiaria tsiafajavonensis 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 : 213-216

10. Brachiaria tsiafajavonensis A. Camus in Bull. Soc. Bot. F rance 72: 622. 1925 (F ig. 10).

Lectotypus (designated here): MADAGASCAR. Reg. Vakinankaratra [Prov. Antananarivo]: mont Tsiafajavona , forêt, 2000 m, V.1922 , Perrier de la Bâthie 14717 ( P [ P00450196 ]!; isolecto-: P [ P00450197 ]!) .

[A: Vorontsova et al. 2397; B: Rokiman et al. 2045; C: Vorontsova et al. 697; D: Vorontsova et al. 1900; E: Mandena 2.XI.2011; F: Hall et al. 17] [Photos: Maria S.Vorontsova]

Stoloniferous mat-forming perennial, prostrate with ascending flowering culms, to 0.5 m high, culms weakly branched, rooting at lower nodes, glabrous. Leaf sheath glabrous to hirsute. Ligule a truncate membrane. Leaf blade lanceolate, chartaceous, 4–16 × 0.6–1.2 cm, glabrous to hirsute on both sides. Inflorescence racemose, slender, contracted, 10– 20 cm long. Racemes 3–7, 3–10 cm long, flexuous, appressed, decreasing in length upwards, on a common axis 5–15 cm long, frequently with short secondary branches, rhachis narrow, scabrous and sometimes pubescent, spikelets overlapping with adjacent spikelets near base of synflorescence, single, on pedicels of uneven length. Spikelets oblong, apically subacute, 2.8–3.5 mm long, whiteish. Lower glume c. ¼ as long as spikelet, membranous, obtuse to acute, 1–3-veined, glabrous separated from rest of spikelet by an internode c. 0.25 mm long, orientation relative to rhachisvariable. Upper glume as long as spikelet, herbaceous, 5-veined, veins dark green, glabrous. Lower floret infertile, palea ⅓– ½ as long as lemma. Lower lemma herbaceous, 5-veined, glabrous. Upper lemma obtuse to acute, smooth, shiny, pale, with apical green crest and some trichomes.

Distribution and ecology. – Madagascar endemic occurring in the central highlands, northern, and eastern areas, in the shade under mature wet mid-elevation and montane forest, often associated with isolated forest fragments, on gneiss and clay, at elevations of 650–2300 m (F ig. 9).

Notes. – Brachiaria tsiafajavonensis is a fairly common species of upland wet forest understory recognised by its oblong spikelet shape as well as its wide leaf blades. F orms with dark purple stripes across the spikelets are sometimes found. It differs from the southern low elevation species B. humbertiana A. Camus by its fully smooth upper lemma, plant rooting at lower nodes, and lower glume only ¼ of the spikelet length, as well as the internode between the glumes shorter than that of B. humbertiana . The plastid DNA regions analysed by HACKEL et al. (2018) indicate a close relationship with the drier habitat species B. comorensis (Mez) A. Camus , with similarly broad leaf blades, and elliptic-oblong spikelets, glumes shorter than ⅓ of the spikelet length, and smooth upper lemmas.

Selected specimens examined. – MADAGASCAR. Reg. Alaotra-Mangoro [Prov. Toamasina]: Mantadia NP, Tsakoka trail, 16.III.2016, Vorontsova et al. 1856 ( K, P, TAN) ; Mantadia NP, c. 1 km past the entrance to the Chute Sacrée , 5.VIII.2019, Vorontsova et al. 2403 ( K, TAN) . Reg. Amoron’i Mania [Prov. Fianarantsoa]: env. D’Ambositra, mont Vatomavy , 23.VII.1928, Humbert & Swingle 4810 ( P) . Reg. Anosy [Prov. Toliara]: Mandrare, vallée de la Manambolo, XII.1953, Bosser 5238 ( P) ; massif du Beampingaratra, vallée de la Maloto , 31.X.1928, Humbert 6313 ( P) ; Andohahela NP, Manongotry, 28 km before Ranomafana , 1.XI.2011, Vorontsova et al. 697 ( K, TAN) . Reg. AIANA [Prov. Antsiranana]: montagne d’Ambre, VII.1953, Bosser 5338 ( K, P) . Reg. Ihorombe [Prov. Fianarantsoa]: Andringitra PN, forêt de Ravaro, 9. I.2000, Messmer et al. 834 ( P) . Reg. Itasy [Prov. Antananarivo]: massif de l’Ankaratra, flanc oriental du Tsiafajavona , 15.VII.1928, Decary et al. 4570 ( K, P) . Reg. SAVA [Prov. Antsiranana]: pentes occidentales du massif de Marojejy, à l’E de Ambalamanasy II, 30.XI.1948, Humbert & Capuron 22281 ( P) . Reg. Sofia [Prov. Mahajanga]: montagnes au N de Mangindrano jusqu’aux sommets de Ambohimirahavavy, 19. I.1951, Humbert & Capuron 25249 ( P) . Reg. Vakinankaratra [Prov. Antananarivo]: Manjakatompo, III.1961, Bosser 15116 ( K, P) . Reg. Vatovavy [Prov. Fianarantsoa]: Ranomafana PN, bords de la Namorona, I.1964, Bosser 18926 ( P) .