Echinochloa hubbardii (A. Camus) Voronts.

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 : 218-220

12. Echinochloa hubbardii (A. Camus) Voronts. , comb. nov. (F ig. 11B–C).

Brachiaria hubbardii A. Camus in Bull. Soc. Bot. F rance 94: 40. 1947. Acroceras hubbardii (A. Camus) Clayton in Kew Bull. 34: 557. 1980. Panicum hubbardii (A. Camus) Renvoize in Hautrey et al., F l. Mascareignes 203: 123. 2018.

Lectotypus (designated here): MADAGASCAR. Reg. AIANA [Prov. Antsiranana]: Nosy Be, V.1879, Hildebrandt 2985 ( P [ P02233603 ]!; isolecto-: GOET [ GOET005565 ] image!, K [ K000244701 , K000244702 ]!, P [ P02233606 , P02233612 ]!, US!) . Syntypi: COMOROS. Anjouan: Tsantsany, XII.1921, Decary 810 ( P [ P00216311 ]!) ; ibid. loco, VIII.1923, Waterlot 918 ( P [ P00216314 ]!) . Grande Comore: Vouni , V.1850, Boivin s.n. ( P [ P00216307 ]!) . MADAGASCAR. Reg. Analanjirofo [Prov. Toamasina]: Sainte Marie , V.1852, Boivin s.n. ( P [ P02233596 ]!) . MAYOTTE: Majimbini forest, V.1884, Humblot 1092 ( P [ P00216308 , P00216309 , P00216310 ]!) ; ibid. loco, s.d., Boivin s.n. ( K [ K000805482 ]!) . TANZANIA. Zanzibar: XI.1 8 7 3, Hildebrandt 1100 (GOET [GOET005564] image!, P [P00442051]!).

= Brachiaria hubbardii var. halophila A. Camus in Bull. Soc. Bot. F rance 101: 395. 1954. Holotypus: MADAGASCAR. Reg. Boeny [Prov. Mahajanga]: Anjiajia, VIII.1952, Bosser 3500 (P [ P02233608 ]!; iso-: K [ K000244703 ]!).

= Brachiaria nodosa Renvoize & Bosser in Hautrey et al., F l. Mascareignes 203: 139. 2018, syn. nov. Holotypus: MAURITIUS: Serpent Island, XII.1971, Vinson s.n. (MAU [ MAU15188 ] image!).

Stoloniferous mat-forming perennial, prostrate with ascending flowering culms, to 20 cm high, culms much branched, rooting at nodes, glabrous, nodes bearded. Leaf sheath glabrous to pubescent. Ligule absent. Leaf blade linear, membranous, 1–4 × 0.1–0.2 cm, glabrous to pubescent on both sides. Inflorescence capitate, 0.5–1.5 cm long, with 5–15(–30) spikelets. Racemes 1–4, 0–0.3 cm long, barely separable within capitate inflorescence, on a common axis 0–1 cm long, with no secondary branching, rhachis narrow, glabrous, spikelets overlapping with adjacent spikelets, single, subsessile. Spikelets elliptic, apically acute, 2–2.3 mm long, white to pale green. Lower glume ½–⅔ as long as spikelet, membranous, acute, 3–5-veined, glabrous or sometimes apically pubescent, orientation relative to rhachis variable. Upper glume as long as spikelet or a little shorter, membranous, pinched at apex, 5–7-veined, glabrous or sometimes apically pubescent. Lower floret male, palea as long as lemma, anthers 3, c. 1.2 mm long. Lower lemma membranous, pinched at apex, 5–7-veined, glabrous or sometimes apically pubescent. Upper lemma acute, smooth, shiny, white becoming pale brown, with an apical green crest.

Distribution and ecology. – Sea shores, associated with puddles and temporary water bodies. Readily forms short dense grazing lawns and turf. F requently associated with human activity and commonly seen on pavements, between paving slabs, and within local pastures and sports turf. Not recorded in Tanzania since Hildebrandt 1100, the single syntype collection made in 1873 (F ig. 9).

Notes. – Echinochloa hubbardii (A. Camus) Voronts. is recognised by its long-exserted capitate inflorescences, short soft leaf blades, and diminutive mat-forming habit. The complete absence of a ligule is consistent with the HACKEL et al. (2018) phylogenetic placement of this species in Echinochloa, a genus commonly lacking a ligule.

Echinochloa hubbardii is sympatric with the closely related miniature trailing Mascarene species E. serpens (Kunth) Voronts. (comb. nov., see below), which is also occasionally present in Madagascar and has similar globose inflorescences and lacks of ligule but sessile inflorescences with fewer spikelets, and with glumes and lower lemma which are always pilose. F rom the overall appearance of the plants it is quite clear that E. hubbardii and E. serpens are closely related, and different from all the other species in Acroceras, Brachiaria, Echinochloa , Panicum s.l., and Urochloa . This relationship between Echinochloa hubbardii and E. serpens was previously obscured by the traditional generic concepts and thus confusingly variable generic placements of these species in Brachiaria [ B. hubbardii A. Camus in BOSSER, 1969], Acroceras [A. hubbardii (A. Camus) Clayton in CLAYTON & RENVOIZE, 1982], and Panicum as well as Brachiaria [ Panicum hubbardii (A. Camus) Renvoize , Brachiaria serpens (Kunth) C.E. Hubb. , and B. nodosa Renvoize & Bosser in BOSSER & RENVOIZE, 2018].

Brachiaria nodosa is morphologically consistent with Echinochloa hubbardii but with more indumentum on the distal parts of its spikelets than average, thus similar to E. serpens but with exserted inflorescences and longer spikelets. The type of Brachiaria hubbardii var. halophila A. Camus displays densely hirsute leaf sheaths and leaf blades and thus a paler specimen colour, but no other differences are observed.

Many of the older specimens of both Echinochloa hubbardii and E. serpens are annotated as “Panicum conglomeratum L.” and a specimen of E. hubbardii is present in the Linnaean herbarium: Herb. Linn. 80.29 [http://linnean-online.org/1261]. Due to confusion with the sympatric and superficially similar Sacciolepis indica (L.) Chase, the name Panicum conglomeratum L. is illegitimate and referrable to Sacciolepis indica (HUBBARD & VAUGHAN, 1940; CAFFERTY et al., 2000; JARVIS, 2007). The lectotype of Brachiaria hubbardii is designated here for its superior quality material and also to maintain continuity with BOSSER & RENVOIZE (2018) who cited Hildebrandt 2985 at P as the holotype.

Selected specimens examined. – MADAGASCAR. Reg. Betsiboka [Prov. Mahajanga]: massif causses du Kelifely , XI.1974, Morat 4671 ( P) . Reg. Boeny [Prov. Mahajanga]: Anjiajia , VIII.1952, Bosser 3500 ( K, P) ; Madirovalo , VI.1901, Perrier de la Bâthie 168[a] ( K) . Reg. AIANA [Prov. Antsiranana]: vallée de l’Ifasy en aval d’Anaborano , 31.III.1951, Humbert & Capuron 25864 ( P) ; Nosy Be, dans la rue de Helville , VIII.1933, Perrier de la Bâthie s.n. ( P, TAN) ; Ambilobe, roadside opposite Jovenna petrol station, 11.X.2011, Vorontsova et al. 347 ( K, TAN) . Reg. Menabe [Prov. Toliara]: environs de Morondava , IX.1956, Bosser 9918 ( P) .