Senecio marinae J. Calvo & Callm., 2023

Calvo, Joel & Callmander, Martin W., 2023, Novelties from the Northern Mountains Complex of Madagascar VII: A new species of Senecio L. (Compositae), Adansonia (3) 45 (16), pp. 279-283 : 280-283

Senecio marinae J. Calvo & Callm. , sp. nov.

( Figs 1 ; 2 )

Senecio marinae sp. nov. can be distinguished by its scrambling or ascending habit with stems 1-4 m long, the oblanceolate to obtrullate, fleshy, glabrous leaves, usually somewhat tricuspidate apically, the synflorescences with subumbelliform divisions, the discoid capitula with 10-11 involucral bracts, and the glabrous achenes. It mostly differs from the similar species S. francoisii Humbert and S. handiensis Forssk. in having discoid capitula.

TYPE. — Madagascar. Boeny Region [Prov. Mahajanga]: Bealanana, Mangindrano , Ambohimirahavavy , Antsahivo , W du campement 01, Matsabory , 14°24’12”S, 49°03’56”E, 1980 m, 20.X.2005, Wohlhauser, Callmander & Buerki 785 (holo-, G [ G00398286 ]!; iso-, MO [ MO-3401237 ] image!; P [ P02473236 ]!; TAN) .

PHENOLOGY. — The new species has been found in bloom in October and November.

DISTRIBUTION AND ECOLOGY. — Senecio marinae , sp. nov. is known at elevations of 1365-2375 m in Ambohimiravavy, Biempoko, Sorata, and Tsaratanana massifs. The new species grows on plateaux and ridges in open forests (chablis) rich in Bamboo in medium altitude moist evergreen forest and at the transition between these forests and the ericoid mountain thicket (sensu Gautier et al. 2018).

ETYMOLOGY. — The epithet marinae honors Marina Rabarimanarivo , botanist at the Missouri Botanical Garden in Antananarivo who contributes immensely to the Madagascar Catalogue project ( Madagascar Catalogue 2023) and understood that the collections from high altitudes in Northern Madagascar represented a new species when she evaluated the genus Senecio for the project in 2009.

CONSERVATION STATUS. — Senecio marinae , sp. nov. has an estimated EOO of c. 1319 km ², an AOO of 24 km ², and five locations encompassed within the COMATSA Nord and Tsaratanana protected areas. Fires are known to occasionally enter pristine forests in those protected areas and are also known along pastures and summit zones ( Goodman et al. 2018). Due to the plausible threats to its habitat for slash-and-burn agriculture and fires caused by lightning, S. marinae , sp. nov. is assigned to a preliminary risk of extinction status of “Vulnerable” [VU B1ab(i,ii,iii,iv,v)+2ab(i,ii,iii,iv,v)] using the IUCN Red List Categories and Criteria ( IUCN 2012).

ADDITIONAL SPECIMENS EXAMINED. — Madagascar. Diana Region [Prov. Antsiranana]: Marotolana, Ambanja , Tsaratanana massif, S slopes, 14°02’53”S, 48°57’04”E, 2211-2365 m, 5.XI.2000, Antilahimena et al. 653 ( G!, K, MO [ MO798854 ] image!, P [ P02473228 ]!, TAN image!); Tsaratanana, XI.1966, Morat 2256 ( TAN image!); Manambato, à 10 km à vol d’oiseau du fkt. Antsahavalany , [Sorata], 13°43’28”S, 49°22’43”E, 1559 m, 25.X.2007, Randriambololomamonjy et al. 103 ( MO [ MO3401222 ] image!, P [ P04276661 ]!, TAN). — Sava Region [Prov. Antisranana]: 22 km à l’E de Bealanana , montagne de Beampoko , 14°13’41”S, 49°08’14”E, 1991 m, 17.XI.2005, Randrianarivelo et al. 329 ( MO, P [ P02473238 ]!, TAN) ; plateau entre Beampoko et Ambohimirahavavy , 14°12’07”S, 49°07’05”E, 2220 m, 9.XI.2005, Randrianarivony et al. 74 ( G!, MO, P [ P02473237 ]!, TAN) ; Andrafainkona, forêt dense humide de Sorata , 1.X.2007, 13°40’57”S, 49°26’33”E, 1364 m, Razakamalala et al. 3634 ( MO [ MO3185014 ] image!, P [ P04276663 ]!, TAN) .

DESCRIPTION

Suffrutescent subshrub, scrambling or ascending, 1-4 m tall. Stem terete, smooth, fistulous (at least upper parts), glabrous, with leaves only on upper part as plant ages. Leaves alternate, simple, pseudopetiolate; laminas oblanceolate to obtrullate, usually somewhat tricuspidate apically, 6-13 × 2.3-5.5 cm, base attenuate, apex acute, margins entire, glabrous on both faces, with venation barely noticeable, fleshy, shiny in living plants; pseudopetioles 1-2.5 cm long, glabrous.Synflorescences corymbiform in overall shape, with divisions subumbelliform; synflorescence bracts linear-subulate. Capitula discoid on peduncles 6-10 mm long with 1-3 bracteoles. Involucres cylindrical, 8-9 × 4-5 mm, glabrous; receptables flat, somewhate fimbrillate; involucral bracts 10-11, linear-oblong, 5.8-7.4× 0.6-1 mm, glabrous; supplementary bracts (calyculus) 3-5, linear-subulate, 1.5-2.3 × c. 0.3 mm, glabrous. Florets c. 22, hermaphrodite; corollas 5.7-6.2 mm long, tubular, limbs c. 2.7 mm long, 5-lobed, yellow; filament collars balustrifrom; anthers 1.5 mm long (including appendage), bases caudate, a half as long as the filament collar, yellowish, appendages c. 0.3 × 0.2 mm; style branches truncate with a crown of sweeping trichomes, yellowish. Achenes cylindrical, c. 1.7 × 0.3 mm (immature), c. 9-ribbed, glabrous; pappus 5.8-6.2 mm long, barbellate, white.

NOTES

In its habit and leaf morphology, Senecio marinae , sp. nov. presents morphological affinities with both S. francoisii Humbert and S. hadiensis Forssk. [synonym of S. petitianus A. Rich. ]. These species are characterized by having a scrambling or ascending habit, fleshy, pinnatinerved leaves, and radiate capitula. Humbert (1963) treated them as the only members of his informal Senecio group XIV. The new species, however, clearly differs in having discoid capitula. In addition, S. marinae , sp. nov. differs from S. francoisii in stem length (1-4 m vs 0.2-0.3 m in S. francoisii ), leaf size (6-13× 2.3-5.5 cm vs 3-8 × 1.2-2.5 cm in S. francoisii ), and involucral bract length (5.8-7.4 mm vs 5-5.4 mm in S. francoisii ). With respect to S. hadiensis , the new species further differs in the involucral bract length (5.8-7.4 mm vs 3.7-4.2 mm in S. hadiensis ). The variety with discoid capitula described from Comoros under the name S. petitianus subvar. discoideus Humbert , can be also differentiated by the remarkable shorter involucral bracts; it has not been recorded in Madagascar. It is interesting to note that S. francoisii , the Malagasy populations of S. hadiensis , and the new species display caudate anther bases.

The new species seems to be restricted to the northern mountains of Madagascar, whereas S. francoisii is distributed through the central-east Madagascar and S. hadiensis in the centre and south-east part of the island. Their distributions areas do not overlap.

Figures

FIG. 1. — Senecio marinae J. Calvo & Callm., sp. nov.: A, flowering stem; B, capitulum at an early stage; C, capitulum at an advanced stage;D, achene with pap- pus; E, floret (ovary and pappus removed); F, anther (notice the caudate base). A, C, D, Antilahimena et al. 653; B, E, F, Wohlhauser et al. 785. Drawing: Roger Lala Andriamiarisoa. Scale bars: A, 1 cm; B, C, 6 mm; D, 2 mm, E, 1.5 mm, F, 0.5 mm.

FIG. 2. — Field pictures of Senecio marinae J. Calvo & Callm., sp. nov.: A, habit; B, synflorescence; C, detail of the capitulum; A-C, Wohlhauser et al. 785. Photographs: S. Wohlhauser.