Humbertacalia madagascarensis Y.L. Peng & Li Bing Zhang, 2016

Peng, Yu-Lan & Zhang, Li-Bing, 2016, Humbertacalia madagascarensis sp. nov. (Asteraceae: Senecioneae) from Madagascar, Phytotaxa 283 (3), pp. 291-294 : 291-294

Humbertacalia madagascarensis Y.L. Peng & Li Bing Zhang , sp. nov. ( Figure 1 )

Type:— MADAGASCAR. Antsiranana: Nature Reserve Integerale Marojejy, 10.5 km NW of Manantenina, along tributary at head of Andranomifotora River, camp 4, 14°26 ′ 24 ″ S, 49°44 ′ 30 ″ E, 1625 m, 4–13 November 1996, P. J. Rakotomalaza, N. Messmer & D. Ravelonarivo 850 (holotype MO-5815272!).

Diagnosis:— Humbertacalia madagascarensis is similar to H. voluta in having brown tomentum and short peduncles, but is different from the latter in having much longer coriaceous involucres, yellowish pappus, larger coriaceous and abaxially purple leaves and leaf blades elliptic, cuneate and oblique at base.

Liana, stem terete and woody, clothed with brown tomentum, leaves alternate, irregularly spaced, petioles 2–5 cm long, densely coated with persistent brown tomentum, leaves coriaceous, blades elliptic, (5) 7–10 cm × 2 (3.5)– 5 cm, apices acute, margins involute, repand, cuneate and oblique at base, venation pinnately reticulate, midrib projecting on both sides, secondary veins 4–6 on each side, conspicuous, projected on dorsal surface, anastomosing arc some distance from the edges, tertiary network fine, anastomosing and sometimes hardly distinct, leaves glabrous above, abaxially purple and densely clothed with brown tomentum, partially persistent; capitula numberous, almost with short peduncles densely clothed with tomentum, persistent, 1–2.5 mm long, rarely sessile, capitula arranged in diffuse panicles with 1–2 threadlike bracts, panicles terminal and axillary, principal rachis slightly zigzag, secondary axes almost straight, bracts and bracteoles small, 2–4 mm long, involucres campanulate, phyllaries 8, 5–6.5 mm × 1.5 mm, lanceolate, coriaceous, densely coated with thick persistent brown tomentum, florets 10–20 per capitulum, tubular, 0.8–1 mm long, yellow, achene brown, glabrous, 1mm long; pappus yellowish, 2 mm long. Peduncles, bracts, involucres and rachis clothed with brown tomentum, persistent.

Discussion:— Humbertacalia is a genus not well studied. The relatively comprehensive research is by Humbert (1963) who treated it as Senecio group XIII. Although Madagascar Catalogue (2013) added some information of habitats and distribution of this genus, the taxonomy of Humbertacalia is still problematic. In fact, after we examined all the specimens, some identification of specimens appeared to be obviously incorrect. The holotype of H. madagascarensis was identified as H. leucopappa on the herbarium sheet by H. Beentje. One of the collectors of the specimen, P.J. Rakotomalaza, suspected it as a “ sp. nov. ”. Our study shows that the new species is distinct from H. leucopappa in having the leaves coriaceous, leaf blades elliptic, larger [(5–)7–10 × (2–) 3.5–5 cm], and with margins slightly involute and repand, capitula usually with short peduncles (1–2.5 mm), involucres much longer (5–6.5 mm), coriaceous, and densely coated with persistent brown tomentum, and pappus yellowish ( Table 1). In contrast, H. leucopappa has the leaves subcoriaceous, leaf blades ellipticlanceolate, smaller (5–8 × 2–3 cm), and with margins entire or sparsely serrate (with 2–8 teeth on each side), capitula sessile or subsessile, involucres shorter (2–3 mm), subcoriaceous, and smooth or slightly woolly, and pappus white. In fact, H. madagascarensis is most similar to H. voluta in having a brown tomentum and short peduncles (1–2.5 mm), but the former is significantly different from the latter in having the leaves coriaceous and abaxially purple, leaf blades elliptic, larger [(5–)7–10 × (2–) 3.5–5 cm)], cuneate and oblique at base, and abaxially clothed with partially persistent brown tomentum, involucres much longer (5–6.5 mm) than pappus (2 mm) and coriaceous, and pappus yellowish. In comparison with H. madagascarensis , H. voluta has the leaves subcoriaceous and abaxially green, leaf blades lanceolate, smaller [(2–)5–7.5 × (1.5–)2–3(–4.5) cm] and rounded at base, and abaxially clothed with persistent brown tomentum, involucres (4–4.5 mm long) almost as long as the pappus and subcoriaceous, and pappus white ( Table 1). Humbertacalia voluta and H. leucopappa morphologically resemble each other in the blade shape and distribution. Sometimes the two species are confused by some researchers. But the two species are significantly different in that the capitula are sessile or subsessile, leaf blades abaxially glabrous, or sometimes clothed with thick or thin partially persistent white tomentum in H. leucopappa , while in H. voluta the capitula are on short peduncles, abaxially clothed with persistent brown tomentum ( Table 1).

The distributions of H. voluta and H. leucopappa are similar according to the field collection records. Both species were observed to grow in humid and subhumid forests in Antsiranana, Fianarantsoa, Mahajanga, Toamasina, and Toliara, but H. leucopappa is more widely distributed and has a larger elevation range ( Table 1). Humbertacalia madagascarensis so far is only found in Antsiranana.

Figures

FIGURE 1. Line drawing of Humbertacalia madagascarensis Y.L. Peng & Li Bing Zhang. A. Habit. B. Leaf. C. Capitulum. D. Achene and pappus (A & B based on the holotype, C & D drawn by Y.L. Peng based on the holotype).