Panicum ibitense A. Camus

Vorontsova, Maria S., 2018, Revision of the group previously known as Panicum L. (Poaceae: Panicoideae) in Madagascar, Candollea 73 (2), pp. 143-186 : 163

15. Panicum ibitense A. Camus in Bull. Soc. Bot. France 72: 371. 1925 ( Fig. 6B , 9 ).

Lectotypus (designated here): MADAGASCAR. Prov. Antananarivo: Mont Ibity, I.1914, Perrier de la Bâthie 10771 ( P [ P00450269 ]!; isolectotype: K [ K000244700 ]!, P [ P00450270 ]!, TAN [ TAN000389 ]!, US [ US00147890 ]!) .

Scandent ascending perennial, with wiry branching stems and an underground bulb 5–8 mm in diameter, to 70 cm long, with glabrous stems and nodes, the nodes enlarged near the base and sometimes finely pilose when young. Leaf sheaths glabrous. Ligule membranous, truncate. Leaf blades linear, flat or rolled, firm, 1–8 × 0.1–0.4 cm, glaucous, dehiscing at the base of the leaf sheaths, scaberulous on both sides. Panicles terminal, fully exserted, 10–20 cm long, ovate, the branches wiry, glabrous. Spikelets ovate, apically obtuse, 1.5–2 mm long, brown to purple, partly open at maturity. Lower glume 3/4–4/5 as long as the spikelet, truncate to obtuse, with fine cilia at the apex, 3–5-veined, with small prickle hairs on the upper part. Upper glume as long as the spikelet or sometimes 3/4 of the spikelet length, herbaceous, 5-veined, with small prickle hairs on the upper part. Lower floret male, with palea. Lower lemma herbaceous, 5-veined, with small prickle hairs on the upper part. Upper lemma smooth, shiny, pale.

Distribution and ecology. – Endemic to Madagascar’s southern High Plateau (a single collection known from northern Madagascar), common in the frequently burned tapia forest and in open rocky habitats, often on quartz, 800 –1800 m ( Fig. 8B ).

Notes. – This species is unique among Madagascar’s grasses in its unusual adaptation to fire: bases of the culms thicken into woody perennial nodule-like storage organs below the ground. The young plant has short flat leaf blades along the culm which dehisce early, leaving only the wiry stems and inflorescences visible for most of the year. Spikelets also dehisce early. The long lower glume, almost as long as the spikelet, is a useful character for identification.

The Gautier 3011 record from Manongarivo is surprising and seems doubtful. This collection does not have an underground storage organ which could be due young plant age; the late post-flowering stage of the spikelets also decreases reliability.

Other species named after Mount Ibity use the epithet “ibityense” but this was published as “ibitese” and may not be corrected according to Art. 60.9 ( TURLAND et al., 2018).

The lectotype sheet is chosen for its best quality material and annotation by the author.

Additional material examined. – MADAGASCAR. Prov. Antananarivo: PK 40 rte d’Arivonimamo , V.1960, Bosser 14450 ( P [ P02608818 ], TAN) ; ibid. loco, V.1962, Bosser 15596 ( P [ P02325449 ], TAN) ; 60 km on rte de Miarinarivo, V.1962, Bosser 16003 ( P [ P02608815 ], TAN) ; Ambohimanga , 27.III.1921, Decary 159 ( P [ P02608848 ]) ; ibid. loco, 27.III.1921, Decary 162 ( P [ P02608808 ]) ; ibid. loco, 27.III.1921, Decary 165 ( P [ P02608847 ] ; Ibity Massif , 15.II.2003, Schatz et al. 4036 ( P [ P02309339 ], TAN) ; ibid. loco, 17.II.2003, Schatz et al. 4108 ( K [ K000805609 ], P [ P06795901 ]) . Prov. Antsiranana: Manongarivo Reserve, en-dessous d’Ambalafary , 14°04'S 48°17'E, 8.IV.1996, Gautier 3011 ( G, K [ K000805463 ], P [ P06795994 ], TAN) . Prov. Fianarantsoa: entre Ambatofinandrahana et Itremo , IX.1956, Bosser 9780 ( TAN) ; 45 km avant Ambositra, XII.1963, Bosser 18750 ( P [ P02608814 ], TAN) ; Ranohira , Isalo , PK 713 , III.1964, Bosser 19125 ( P [ P02608816 ], TAN) ; Itremo , IV.1964, Bosser 19562 ( P [ P02608812 ], TAN) ; 54 km E of Ambatofinandrahana, 25.I.1975, Croat 29644 ( TAN) ; pentes occidentales à Faliarivo , III.1934, Humbert 14502 ( P [ P02608809 ]) ; plateaux et vallées de l’Isalo , 29.I.1955, Humbert 29 757 ( P [ P03487887 ], TAN) ; montagnes à l’W d’Itremo , Humbert 30077 ( P [ P02608806 ]) ; ibid. loco, 17.I.1955, Humbert 30080 ( G, P [ P02608844 ], TAN) ; Itremo, Ambatoantrano , 20°34'11"S 46°34'51"E, 17.III.2013, Nanjarisoa & Andriamampionona 49 ( K, TAN) ; Itremo, Ampangabe , 20°36'41"S 46°36'34"E, 15.II.2014, Nanjarisoa et al. 114 ( K, TAN) ; Itremo, Soatsihotapaka , 20°31'33"S 46°34'54"E, 20.II.2014, Nanjarisoa et al. 153 ( K, TAN) ; Itremo, Ianasana , 20°34'41"S 46°35'05"E, 13.III.2012, Ratovonirina et al. 171 ( K, TAN [ K000753861 ]) ; ibid. loco, 13.III.2012, Ratovonirina et al. 189a ( K, TAN [ K000753879 ]) ; Isalo, 1.7 km from Namaza camp on the trail to the Blue and Black Pools, 22°32'15"S 45°22'31"E, 17.XII.2013, Vorontsova et al. 1315 ( TAN) ; Itremo, Ambatoasira , 20°36'44"S 46°34'26"E, 20.V.2014, Vorontsova et al. 1582 ( TAN) ; Itremo , IV.1921, Waterlot 106 ( P [ P02608846 ]) . Prov. Toamasina: près de la gare de Masse , Bosser 16588 ( P [ P02608820 ], TAN) ; Ambatovy , I.1972, Bosser 21115 ( P [ P06795997 ]) ; ibid. loco, V.1969, Morat 3245 ( P [ P02307366 ]) ; Mangoro , II.1925, Perrier de la Bâthie 16886 ( P [ P02608845 ]) ; Ambatovy , 18°48'48"S 48°19'40"E, 23.II.2005, Rakotovao et al. 1362 ( K [ K000805485 ], P [ P06768481 ]) ; Ambatovy, commune rurale Ambohibary , 18°51'14"S 48°18'50"E, 22.II.2005, Razanatsoa et al. 244 ( G, P [ P06768480 ]) .

Figures

Fig. 6. – A. Panicum cupressifolium A. Camus; B. Panicum ibitense A. Camus; C. Panicum luridum Hack.; D. Panicum mitopus K. Schum. [A: Nanjarisoa et al. 87; B: Letsara et al. 2047; C: Rakotoarisoa & Randrianavosoa SNGF 2931; D: Vorontsova et al. 2110] [Photos: A–B, D:M.S. Vorontsova; C: S. Rakotoarisoa]

Fig. 9. – Panicum ibitense A. Camus. A. Habit; B. Culm base below ground, enlarged; C. Node, enlarged; D. Ligule; E. Flowering branch; F. Spikelet; G. Spikelet with glumes removed; H. Lower glume, dorsal view; I. Lower glume, ventral view; J. Upper glume, dorsal view; K. Upper glume, ventral view; L. Lower lemma, dorsal view; M. Lower lemma, ventral view; N. Lower floret stamens; O. Upper floret, ventral view; P. Upper floret, lateral view; Q. Upper lemma, dorsal view; R. Upper lemma, ventral view; S. Upper palea, dorsal view; T. Upper palea, ventral view. [Ratovonirina et al. 171, K] [Drawing: Lucy T. Smith]

Fig. 8. – Distribution maps. A. Panicum cupressifolium A. Camus (stars), P. danguyi A. Camus (triangles), P. dregeanum Nees (circles) and P. flacourtii A. Camus (squares); B. Panicum humbertii A. Camus (stars), P. humile Nees ex Steud. (triangles), P. ibitense A. Camus (circles) and P. inconspicuum Voronts. (squares).