Humbertacalia racemosa (Bojer ex DC.) 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 : 106-108

9. Humbertacalia racemosa (Bojer ex DC.) C. Jeffrey

( Fig. 5 )

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

Cacalia racemosa Bojer ex DC. , Prodromus Systematis Naturalis Regni Vegetabilis 6: 330 ( Candolle 1838). — Senecio exsertus Sch. Bip. , Flora 28: 499 ( Schultz Bipontinus 1845), nom. nov., non Senecio racemosus (M. Bieb.) DC. , Prodromus Systematis Naturalis Regni Vegetabilis 6: 358 ( Candolle 1838).

— Typus: Madagascar. Prov. Fianarantsoa, forêts de la province de Betsilau [ Betsileo ], 1835, fl., Bojer s.n. (holo-, G-DC [ G00471391 ]!; iso-, P [ P00557715 , fragm.]!) .

Cacalia leucopappa Bojer ex DC. , Prodromus Systematis Naturalis Regni Vegetabilis 6: 330 ( Candolle 1838). — Senecio leucopappus (Bojer ex DC.) Humbert , Mémoires de la Société linnéenne de Normandie 25: 140 ( Humbert 1923). — Humbertacalia leucopappa (Bojer ex DC.) C. Jeffrey , Kew Bulletin 47 (1): 83 ( Jeffrey 1992), comb. inval. [ Turland et al. 2018: ICN Art. 41.5] — Humbertacalia leucopappa (Bojer ex DC.) Pruski , Phytoneuron 2021-65: 19 ( Pruski 2021), syn. nov.

— Typus: Madagascar. Province Fianarantsoa, forêts de la province Betsilau, 1835, fl., Bojer s.n. (holo-, G-DC [ G00471375 ]!; iso-, P [ P00557670 , fragm.]!) ( Fig. 5 ).

Senecio exsertus var. angustifolius Humbert , Notulae Systematicae 15 (4): 371 ( Humbert 1959), syn. nov.

— Typus: Madagascar. Anosy Region [Prov. Toliara], massif du Beampingaratra (Sud-Est), col du Beampingaratra, 1350 m, 31.X-1.XI.1928, Humbert 6262 (holo-, P [ P00835898 ]!) .

ICONOGRAPHY. — Humbert (1963: 761, fig. 139, 14-15, sub Senecio exsertus ).

ETYMOLOGY. — The epithet racemosa refers to the synflorescence type of this species, although it is strictly narrowly paniculiform rather than racemiform.

VERNACULAR NAMES. — Unknown.

DISTRIBUTION AND ECOLOGY. — Humbertacalia racemosa occurs in subhumid bioclimate, in central plateau, southeastern and eastern of Madagascar (Alaotra-Mangoro, Ihorombe and Vakinankaratra Regions). It grows in sclerophyllous woodland or remnant medium altitude moist evergreen forest, usually on hillsides, at elevations around 600 to 1800 m.

CONSERVATION STATUS. — Humbertacalia racemosa has an extent of occurrence (EOO) of c. 23 857 km 2, an area of occupancy (AOO) of 16 km 2, and four locations with respect to the most serious plausible threat of agriculture. Even though one subpopulation occurs within the protected area of Ankaratra-Manjakatompo, the species habitat of the other three subpopulations is threatened by agriculture, fire and logging; all of which will result in inferred continuing decline in its EOO, AOO, habitat quality, number of subpopulations, and number of the mature individuals. In addition, this species is only known from six old herbarium specimens, no recent collection is recorded. Humbertacalia racemosa is therefore assessed as “Endangered” [EN B2ab(i,ii,iii,iv,v)] according to IUCN Red List Categories and Criteria ( IUCN 2012).

ADDITIONAL SPECIMENS EXAMINED. — Madagascar. Alaotra-Mangoro Region [Prov. Toamasina]: Ambatondrazaka, Onibe [17°50’S, 48°33’E], 1000 m, VIII.1938, fl., Cours 908 ( P [ P02397480 ]) . — Ihorombe Region [Prov. Fianarantsoa]: Ifandana, Pce. de Farafangana , [22°49’S, 47°07’E], 6.IX.1926, fl., Decary 5222 ( P [ P02397479 , P04391739 ]) . — Vakinankaratra Region [Prov. Antananarivo]: Tsinjoarivo sur la colline du Rova, [19°37’S, 47°41’E], 8.X.1966, fl., Jacquemin H153 J ( P [ P02397478 ]) ; Manjakatompo , [19°22’S, 47°18’E], fl., Service Forestier s.n. ( TEF) .

DESCRIPTION

Leaves petiolate; leaf laminas 4-8× 2.2-3.5 cm, lanceolate to elliptic, base obtuse to rounded, apex acute, margins entire, glabrous on both surfaces, venation pinnate (conspicuous on both surfaces, including tertiary veins), rather coriaceous; petioles up to 1 cm long. Synflorescences axillary and terminal, narrowly thyrsoid-paniculiform. Capitula pedunculate (peduncles 2-5 mm long); involucres campanulate, glabrous; involucral bracts 8(-9), 3.6-4 × 0.8-1.2 mm; supplementary bracts 4-6, 0.8-1 mm long. Florets c. 20, 3.9-4 mm long; corollas tubular, 5-lobed, whitish (somewhat purplish?); anther bases long-caudate, almost twice longer than filament collar; style branches obtuse with a crown of sweeping trichomes. Achenes c. 1.3 × 0.4 mm (immature), rather cylindrical, glabrous, straw-coloured; pappus c. 4.2 mm long, whitish.

NOTES

The name Cacalia leucopappa Bojer ex DC. has widely been misinterpreted, probably due to the species concept established by Humbert. According to Humbert (1923, 1963), this species displays mostly sessile capitula arranged in subglobose glomerules; collections cited by him as Forsyth Major 56 and Humbert & Capuron 25733 perfectly fit with such morphology. This is in contrast to the information provided in the protologue by Candolle (1838) based on the type (Bojer s.n., forêts de la province de Betsilau [Betsileo], 1835), where the capitula are described as follows: “paniculae ramis racemosis, pedicellis capitulo brevioribus bracteolas subulatas gerentibus”. The type material shows, indeed, synflorescences racemiform composed of pedunculate capitula, where the distal ones are solitary and the proximal ones are arranged in groups of 2-3 that, in turn, are shortly pedunculate ( Fig. 5 ). The peduncles bear a few linear, 1.5-2.5 mm long bracteoles (sometimes only one at the base). These characters do not support Humbert’s concept of C. leucopappa , but perfectly match those of C. racemosa . In fact, Candolle stated at the end of the protologue of C. leucopappa : “Valdè affinis C. racemosae sed folia 2 ½ poll. longa. pollicem lata. Cor. flavidae in specim. juniores”. Comparing both protologues, one realizes that they are very similar in describing the leaf venation, the synflorescence type, the bracteoles, the involucral bract number, and the floret number, only slightly differing in leaf size and floret color. The difference regarding leaf size is not significant considering that the type specimen of C. racemosa lacks lower cauline leaves, which usually decrease in size towards the synflorescences (by contrast, note that the single leaf in the holotype of C. leucopappa is not attached to the synflorescence and most probably corresponds to a cauline leaf). Likewise, the dissimilarity in floret color (purphish in C. racemosa vs yellowish in C. leucopappa ) might be explained by a confusion. A collection of C. racemosa (Cours 908) clearly indicates that the styles and anthers are yellow and the corollas are white, which might have led Bojer to wrongly describe the corollas as yellowish. On the other hand, it is not rare that whitish corollas take certain purple hues depending on the phenological state. Finally, it is interesting that the two specimens come from the same region, i.e., “forêts de la province de Betsilau” [forests of Betsileo Province]. For all these reasons, C. racemosa and C. leucopappa are considered the same taxonomic entity. Cacalia leucopappa is synonymized with C. racemosa because the traditional usage of this latter name preserves the species concept intended by Candolle.

Humbertacalia racemosa can be distinguished by the combination of the following characters: leaves glabrous with conspicuous venation on both surfaces, capitula pedunculate, involucral bracts 8(-9), 3.6-4 mm long, and c. 20 florets. It shows morphological affinities with H. abbreviata comb. nov., stat. nov. (see comments under this latter species). The collection Miller & Randrianasolo 4392 (MO, P, TAN) matches well the characters of H. racemosa except for its leaves with inconspicuous venation. Additional collections are needed to confirm its placement under this species or if, otherwise, it deserves to be treated as a distinct taxon.

The name Senecio exsertus var. angustifolius based on Humbert 6262 shows an overall similar morphology as Humbertacalia racemosa and is here placed under the latter species.

Figures

FIG. 5. — Holotype of Cacalia leucopappa Bojer ex DC. in G-DC: A, zoom in of the synflorescence branches; B, annotations on the verso of the label in Bojer’s hand. (G00471375; © Herbier, Conservatoire et Jardin botanique de Genève, reproduced with permission).