Humbertacalia C. Jeffrey

Genus Humbertacalia C. Jeffrey Kew Bulletin 47 (1): 82 (Jeffrey 1992). TYPE SPECIES. — Humbertacalia tomentosa (Lam.) C. Jeffrey (basionym: Eupatorium tomentosum Lam.). ETYMOLOGY. — The name Humbertacalia honors the French botanist Henri Humbert (1887-1967), who was devoted to the study of the flora of Madagascar and became the foremost specialist in Malagasy Compositae. The epithet is derived in the same way as some of the other genera of the “ Cacalia ” group (e.g. Monticalia C. Jeffrey, Paracalia Cuatrec., Pentacalia Cass.). DESCRIPTION Plants scandent, woody, with long stems that usually climb or lean over other plants, generally (1)2-4(10) m long, glabrescent or covered with different types of indumentum composed of multicellular trichomes. Stems cylindrical, usually striate, lenticellate or not. Leaves simple, alternate, petiolate (rarely sessile); leaf laminas 3.5-12 × 2-8 cm, oblong, lanceolate, or broadly ovate, base attenuate to cordate (sometimes somewhat truncate), apex rounded to acuminate, margins entire to dentate (usually remotely mucronate-denticulate), plane, glabrous to slightly arachnoid on the adaxial surface, glabrescent to densely lanate on the abaxial surface, venation pinnate or palmate, conspicuous or not, chartaceous to coriaceous, sometimes slightly fleshy; petioles up to 4 cm long. Synflorescences axillary or terminal, thyrsoid-paniculiform or corymbiform. Capitula homogamous, discoid, sessile to pedunculate (peduncles up to 8 mm); involucres cylindrical, cupuliform, or campanulate, glabrous or covered by indumentum; receptacles flat, usually fimbrillate; involucral bracts (3-)5-10(-13), 1.8-5.3 × 0.6-2.4 mm long; supplementary bracts (calycle) (1-)4-8, 0.3-2.4 mm long. Florets (3-)5-20, hermaphrodite; corollas tubular, 5-lobed, mostly whitish; filament collars barely swollen at base; anther bases sagittate to caudate, anther appendages 2-3-times longer than wide; style branches truncate to obtuse with a crown of sweeping trichomes or penicillate, stigmatic areas usually in two bands. Achenes 1.3-3 × 0.4-0.8 mm, rather cylindrical, 5-10-ribbed, glabrous or pubescent, brownish; pappus usually 1-seriate, of capillary bristles, barbellate, whitish. 1. Humbertacalia abbreviata (Humbert) Rabarim., Callm. & J. Calvo , comb. nov., stat. nov. (Fig. 1) Senecio exsertus var. abbreviatus Humbert, Notulae Systematicae 15(4): 370 (Humbert 1959). NOTES — Typus: Madagascar. Ihorombe Region [Prov. Fianarantsoa], Ifandana, [22°49’S, 47°07’E], 6.IX.1926, fl., Decary 5226 (lecto-, designated here, P [P00835897]!; isolecto-, P [P04391738]!; US [US01832483 image]!) (Fig. 1). Pelser et al. (2007) presumed the affiliation of Humbertacalia to subtribe Senecioninae on the basis of its morphology, distribution, and karyology. Although some exceptions exist, the subtribe Senecioninae includes genera characterized by having a balustriform filament collar and stigmatic areas in two bands (Nordenstam et al. 2009). The Humbertacalia species has usually stigmatic areas in two bands but the filament collars are barely swollen at the base, indeed, they are rather cylindrical in some species. There are species of Humbertacalia that are extremely variable in leaf shape and indumentum, which makes that these characters become barely useful for distinguishing certain species. On the other side, the character sessile/pedunculate capitula appears to be useful for species separation, however, few specimens remain unidentified because they show a combination of characters that do not match the accepted species as currently circumscribed. Phylogenetic information of this group may contribute to elucidate the species relationships and it could also involve some adjustments in the present taxonomic treatment. KEY TO THE SPECIES OF HUMBERTACALIA C. JEFFREY 1. Leaves palmately 3(-5)-veined; style branches penicillate; achenes pubescent............................................................................................................................................................. 10. H. tomentosa (Lam.) C. Jeffrey — Leaves pinnately veined; style branches with a crown of sweeping trichomes; achenes mostly glabrous........ 2 2. Leaves subsessile, base amplexicaul to semi-amplexicaul.................... 2. H. amplexifolia (Humbert) C. Jeffrey — Leaves petiolate, base attenuate to subcordate.............................................................................................. 3 3. Involucral bracts 5; leaves glabrous, coriaceous............................................................................................ 4 — Involucral bracts 8-13; leaves glabrous or with indumentum, coriaceous or chartaceous.............................. 5 4. Capitula pedunculate, not clustered; peduncles 2-4 mm long........... 7. H. neoalleizettei (Humbert) C. Jeffrey — Capitula sessile or subsessile, usually arranged in glomerules............. 8. H. pyrifolia (Bojer ex DC.) C. Jeffrey 5. Capitula mostly pedunculated, not arranged in glomerules......................................................................... 6 — Capitula sessile or subsessile, usually arranged in glomerules....................................................................... 8 6. Involucral bracts 12-13, arachnoid-floccose (at least at base); leaves initially arachnoid; peduncles 6-15 mm long............................................................ 5. H. diffusa J. Calvo, Rabarim. & Callm., comb. nov., stat. nov. — Involucral bracts 8(-9), glabrous; leaves glabrous; peduncles 1-5 mm long................................................... 7 7. Involucral bracts 1.8-2 mm long; florets c. 10............................................................................................................................................. 1. H. abbreviata (Humbert) Rabarim., Callm. & J. Calvo, comb. nov., stat. nov. — Involucral bracts 3.6-4 mm long; florets c. 20................................... 9. H. racemosa (Bojer ex DC.) C. Jeffrey 8. Involucral bracts 2-3 mm long; leaves glabrous to initially arachnoid on adaxial surface.................................................................................................3. H. apocynifolia (Baker) Rabarim., Callm. & J. Calvo, comb. nov. — Involucral bracts 3.7-5.3 mm long; leaves pilose to tomentose-hirsute (rarely glabrous) on adaxial surface.......... 9 9. Involucral bracts (11-)13, 3.7-4.5 mm long.............................................. 4. H. coursii (Humbert) C. Jeffrey — Involucral bracts 8(-9), 4.4-5.3 mm long.......................... 6. H. madagascarensis Y.L. Peng & Li Bing Zhang ETYMOLOGY. — The epithet abbreviata probably refers to the small involucres of this species. VERNACULAR NAMES. — “Vahimary” (Decary 5226). DISTRIBUTION AND ECOLOGY. — Humbertacalia abbreviata comb.nov., stat. nov. is endemic to the humid and subhumid bioclimatic areas (Cornet 1974) in southeastern Madagascar within the Anosy, Ihorombe and Atsimo-Atsinanana administrative regions. This species grows in lowland and medium altitude moist evergreen forests (sensu Gautier et al. 2018a) on laterite of gneiss, mostly in clearing or forest margins, at elevations of c. 500- 900 m. CONSERVATION STATUS. — Humbertacalia abbreviata comb. nov., stat. nov. has an estimated extent of occurrence (EOO) of 3365 km 2, an area of occupancy (AOO) of 16 km 2 and four locations. Even though the species occurs in the protected areas of Ivohibe, Befotaka – Midongy du Sud and Andohahela, at these sites it is nevertheless threatened by ongoing degradation or destruction of its habitat due to shifting agriculture, annual fire, logging and wood harvesting (Goodman et al. 2018); all of which will result in continuing decline in its EOO, AOO, habitat quality, number of subpopulations and number of mature individuals. Therefore, H. abbreviata comb. nov., stat. nov. is assessed as “Endangered” [EN B 1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v)] according to IUCN Red List Categories and Criteria (IUCN 2012). ADDITIONAL SPECIMENS EXAMINED. — Madagascar. Anosy Region [Prov.Toliara]: Bassin de la Manampanihy (sud-est), Col de Fitana, [24°44’S, 46°51’E], 300-700 m, 15.X.1928, fl., Humbert 6038 (G, P [P02397476, P02397477], TAN, US [US01832484]). — Atsimo-Atsinanana Region [Prov. Fianarantsoa]: Midongy du Sud, forêt d’Anamangy, 23°31’16”S, 47°05’19”E, 640 m, 13.IX.2005, fl., Andrianjafy et al. 1184 (MO, P [P00860315], TAN). — Ihorombe Region [Prov. Fianarantsoa]: Ivohibe, Ambatovita, 4.5 km NE d’Ivohibe, 22°28’08”S, 46°55’34”E, 874 m, 28.XI.2010, fl., SNGF 2649 (K, MO, P, SNGF, TAN, TEF). DESCRIPTION Leaves petiolate; leaf laminas 6-8 × 2.9-4 cm, lanceolate to ovate, base obtuse to rounded, apex attenuate to acuminate, margins entire, glabrous on both surfaces, venation pinnate (conspicuous on both surfaces, including tertiary veins), rather coriaceous; petioles up to 1.8 cm long. Synflorescences mostly axillary, narrowly thyrsoid-paniculiform. Capitula shortly pedunculate (peduncles 1-2.5 mm long); involucres cupuliform, glabrous; involucral bracts 8, 1.8-2 × c. 1 mm; supplementary bracts 4-5, 0.3-0.4 mm long. Florets c. 10, 3.8-4 mm long; corollas tubular, 5-lobed, whitish; anther bases caudate, as long as or slightly longer than filament collar; style branches obtuse with a crown of sweeping trichomes. Achenes c. 2.8 × 0.6 mm, rather cylindrical, c. 9-ribbed, glabrous except for few trichomes on the upper part, straw-coloured; pappus c. 3.7 mm long, whitish. NOTES Humbertacalia abbreviata comb. nov., stat. nov. is well-characterized by the glabrous leaves with conspicuous venation on both surfaces, the shortly pedunculate capitula, and the small involucres with the involucral bracts somewhat fused at the base. It is similar to H. racemosa (Bojer ex DC.) C. Jeffrey, from which it differs in involucre shape (strictly cupuliform, with the bracts somewhat fused at the base in H. abbreviata comb. nov., stat. nov. vs rather campanulate, with the bracts partite along their whole length or almost so in H. racemosa), involucral bract length (1.8-2 mm long in H. abbreviata comb. nov., stat. nov. vs 3.6-4 in H. racemosa), and peduncle length (1-2.5 mm long in H. abbreviata comb. nov., stat. nov. vs 2-5 in H. racemosa), and floret number (c. 10 in H. abbreviata comb. nov., stat. nov. vs c. 20 in H. racemosa). It is interesting to note that the collections Decary 5222 and 5226, which come from the same locality and were collected on the same day, were both treated as belonging to Senecio exsertus var. abbreviatus (Humbert 1963). However, Decary 5222 clearly corresponds to Humbertacalia racemosa. Humbert (1959), when describing the new variety, designated the collection Decary 5226 at P as the holotype of the name. As two specimens corresponding to this collection are kept at P and there is no explicit indication suggesting that Humbert selected one of the two duplicates to serve as holotype, the name S. exsertus var. abbreviatus is lectotypified on the best preserved specimen P 00835897 (Fig. 1).
Published as part of Rabarimanarivo, Marina N., Callmander, Martin W. & Calvo, Joel, 2023, Synopsis of Humbertacalia (Compositae), a genus endemic to Madagascar and Réunion, pp. 93-113 in Adansonia (3) (3) 45 (7) on pages 94-96, DOI: 10.5252/adansonia2023v45a7, http://zenodo.org/record/7774939
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