Humbertacalia coursii (Humbert) C. Jeffrey

Rabarimanarivo, Marina N., Callmander, Martin W. & Calvo, Joel, 2023, Synopsis of Humbertacalia (Compositae), a genus endemic to Madagascar and Réunion, Adansonia (3) 45 (7), pp. 93-113 : 101

4. Humbertacalia coursii (Humbert) C. Jeffrey

Kew Bulletin 47 (1): 83 ( Jeffrey 1992).

Senecio coursii Humbert , Mémoires de l’Institut scientifique de Madagascar, sér. B, 6: 195 ( Humbert 1955).

— Typus: Madagascar. Sava Region [Prov. Antsiranana], massif de l’Anjanaharibe (pentes et sommet nord) à l’ouest d’Andapa (haute Andramonta , bassin de la Lokoho (nord-est), [14°36’S, 49°27’E], 1200 m, 10.XII.1950 - 3.I.1951, bud & fl., Humbert, Capuron & Cours 24660 (lecto-, P [ P00727179 ]! ; isolecto-, P [ P02436224 , P02436225 ]!) . — Pentes occidentales du massif de Marojejy (nord-est), bassin de la Lokoho , à l’est d’Ambalamanasy II, district d’Andapa, [14°27’S, 49°42’E], 450-800 m, 28.XI.1948, fl., Humbert & Capuron 22144 (syn-, P [ P00498764 , P02436230 ]!) . — Fitovinany Region [Prov. Fianarantsoa], Bassin de Matitanana , forêt primitive de Tsianovoha , [21°47’S, 47°21’E], IX.1934, bud & fl., Heim s.n. (syn-, P [ P00727178 ]!) . — Atsinanana Region [Prov. Toamasina], forêt orientale (vestiges), bassin inférieur de Mangoro , [19°42’S, 48°03’E], X.1927, fl. & fr., Perrier de la Bâthie 18123 (syn-, P [ P00727180 , P00727181 ]!) .

ETYMOLOGY. — The epithet coursii honors the French botanist Gilbert Cours-Darne (1909-2001), who participated in collecting the type material with Humbert and Capuron. Cours was trained as an engineer in tropical agronomy and worked in Madagascar from 1931 to 1961 where he discovered numerous species in the company of Humbert.

VERNACULAR NAMES. — “Vahipiretaka” (Heim s.n.).

DISTRIBUTION AND ECOLOGY. — Humbertacalia coursii occurs in humid and subhumid bioclimates, along eastern Madagascar, from Marojejy (Sava Region) in the north to Ivohibe (Ihorombe region) in the south, in medium altitude moist evergreen forest on gneiss and granite substrate, at elevations from 500-1600 m.

CONSERVATION STATUS. — Humbertacalia coursii has an estimated extent of occurrence (EOO) of 16 892 km 2, an area of occupancy (AOO) of 24 km 2, and six locations with respect to the most serious plausible threat of illegal logging and agriculture. Even though, it occurs within the protected areas of Anjanaharibe-Sud, Marojejy and Ivohibe, it is threatened by ongoing degradation or destruction of its habitat due to shifting agriculture, illegal logging and wood harvesting; all of which will result in inferred continuing decline in its habitat quality. Based on current information, H. coursii is therefore assessed as “Vulnerable” [VU B1ab(iii)+B2ab(iii)] according to IUCN Red List Categories and Criteria ( IUCN 2012).

ADDITIONAL SPECIMENS EXAMINED. — Madagascar. Sava Region [Prov. Antsiranana]: Anjanaharibe, Andapa , [14°36’S, 49°27’E], 1200 m, 17.XII.1950, bud & fl., Cours 3698 ( MO, P [ P02397553 ], TAN) ; pentes orientales du Marojejy (NE), à l’ouest de la rivière Manantenina , affluent de la Lokoho, [14°25’45”S, 49°44’22”E], 1450 m, 24.III.1949, ster., Humbert 23649 ( P [ P02397552 ]) . — Ihorombe Region [Prov. Fianarantsoa]: forêt de Marovahy près d’Ivohibe, [22°31’S, 46°59’E], 27.XI.1924, fl., Armand 35 ( P [ P02397554 , P02397555 ]) .

DESCRIPTION

Leaves petiolate; leaf laminas 6-10 × 3-5.1 cm, lanceolate to elliptic, base cuneate to obtuse, apex acute to attenuate (usually mucronate), margins remotely mucronate (entire in overall appearance) to shallowly dentate, tomentose-hirsute on both surfaces (rarely pilose), venation pinnate (conspicuous on abaxial surface), rather chartaceous; petioles up to 3 cm long. Synflorescences axillary and terminal, spiciform. Capitula sessile; involucres campanulate, slightly arachnoid to glabrescent at base; involucral bracts (11-)13, 3.7-4.5 × 0.7- 0.9 mm; supplementary bracts 6-8, 1.5-2 mm long. Florets c. 20, 3.2-3.7 mm long; corollas tubular, 5-lobed, pale greenish; anther bases caudate, almost as long as filament collar; style branches obtuse with a crown of sweeping trichomes. Achenes c. 1.8 × 0.6 mm (immature), rather cylindrical, glabrous, straw-coloured; pappus 3.7-3.9 mm long, whitish.

NOTES

This species is well-characterized by the tomentose-hirsute leaves on both surfaces and the long-spiciform synflorescences with sessile capitula usually arranged in lax glomerules. The trichomes are pluricellular, with the apical part whitish flageliform and caducous and the basal cells permanent and ochraceous. It might be confused with Humbertacalia madagascarensis , but the involucral bract number and length are useful to discriminate each other [(11-)13, 3.7-4.5 mm in H. coursii vs 8(-9), 4.4-5.3 mm in H. madagascarensis ]. Moreover, H. coursii has sessile capitula whereas those of H. madagascarensis are subsessile, sometimes having a short peduncle up to 2 mm long. The trichomes of the leaves and stems are also longer in H. coursii .

Among the syntypes cited in the protologue, the specimen P00727179 (Humbert 24660) is designated as the lectotype because it is taxonomically very informative and the collection consists of three duplicates. The collection Cours 3698 comes from the same gathering (see Humbert’s annotation on the label of P02436225), but it is not considered type material because it is not explicitly mentioned in the protologue.