Contributions to the Andean Senecioneae (Compositae), part III: A new species of Senecio from northern Chile

Joel CALVO ^1,* & Andrés MOREIRA-MUÑOZ ²

^1,2 Instituto de Geografía, Facultad de Ciencias del Mar y Geografía, Pontificia Universidad Católica de Valparaíso, Av. Brasil 2241, 2362807 Valparaíso, Chile.

* Corresponding author: calvocasas@gmail.com, https://orcid.org/0000-0003-2340-7666

² andres.moreira@pucv.cl, https://orcid.org/0000-0002-9136-1391

INTRODUCTIONTOP

The genus Senecio L. (Asteraceae Bercht. & J.Presl, Senecioneae Cass.) in Chile was comprehensively revised for the first time by the Argentinian botanist A.L. Cabrera (Cabrera 1949). He recognized 208 species, which organized under an infrageneric classification based on sections and subsections. A few contributions were done afterwards, mainly concerning the description of new species or new records (e.g., Ricardi & Marticorena (1964); Marticorena & Quezada (1977); Moreira-Muñoz & al. (2016); Muñoz-Schick & al. (2016)). Recently, the new catalogue of the Chilean flora recorded 233 Senecio species (Rodríguez & al. 2018). These numbers are nevertheless tentative and a modern taxonomic revision is still lacking.

As part of ongoing studies on the genus Senecio in the Andes (Calvo & Fuentes 2018; Beltrán & Calvo 2019), we here describe a new species from northern Chile on the basis of morphological evidence. It belongs to the group of the caespitose Senecio and keeps morphological affinities with S. algens Wedd., S. altoandinus Cabrera, and S. cremnicola Cabrera. The new species is only known from El Loa Province (Antofagasta, Chile) and thrives in the desertic ‘puna’ ecoregion. Its presence in the neighboring regions of southern Sur Lípez (Potosí, Bolivia) and Jujuy (northwestern Argentina) is likely, and therefore, further field work in these areas is needed in order to improve the knowledge on its variability and distribution area.

MATERIAL and methodsTOP

This contribution is the result of an intensive revision of herbarium specimens, bibliography, and recent field work carried out in El Loa Province (Antofagasta, Chile). The herbaria visited were CONC and SGO; herbarium acronyms follow Thiers (2019). The main regional treatments consulted for Senecio were Cabrera (1949, 1985) and Freire & al. (2014).

RESULTS AND DISCUSSIONTOP

Senecio toconaoensis J.Calvo & A.Moreira sp. nov. Type: Chile, región de Antofagasta, El Loa, Toconao, cordón S de los cerros de La Pacana, 23°9′28″ S, 67°27′56″ W, 4880 m a.s.l., 4–III–2019, J. Calvo 7911 leg. (holo-: SGO; iso-: CONC, MA, Z). Figs. 1 and 2.

LSID: urn:lsid:ipni.org:names:77201991-1

Within the discoid caespitose species with yellowish anthers, style-branches, and corollas, this species differs in its vertical hypogeous stems, fleshy spatulate leaves, entire or with a few incipient teeth, usually with the distal margin undulate or strongly recurved, its solitary capitula subsessile or short-pedunculate, and the long-pilose achenes.

Caespitose perennial herb. Rhizome 1–3 cm long, oblique. Stems 3–8 cm long, hypogeous nearly the whole length, usually with remnants of old leaves, glabrous, plainly white. Leaves spatulate, long-attenuate into a pseudopetiole, glabrous. Leaf lamina 6.5–9 × 3.6–7 mm, rounded at the apex, attenuate at the base, entire or with 3–6 incipient teeth on the margin, usually undulate or strongly recurved at the distal part (in living plants), with the midrib barely conspicuous, fleshy. Capitulum discoid, solitary, terminal, subsessile or short-pedunculate; involucre 7–9 × 6–7 mm. Involucral bracts 13(14), linear-oblong, 5.6–7 × 1.3–2.3 mm, smooth, glabrous. Supplementary bracts 1–2, linear-subulate, 3–4.5 × 0.4–0.8 mm, a third to a half as long as the involucral bracts, glabrous. Disc florets c. 55, 4.7–5.8 × 0.6–0.9 mm, 5-lobed, yellowish with the lobes deep-red. Anthers rounded, yellowish; filament collar balusterform. Style branches truncate with a crown of sweeping hairs, yellowish except for the abaxial surface that is deep-red. Achenes 3.1–3.8 × 0.7–0.8 mm, long-pilose, with trichomes 0.3–0.35 mm long, white; pappus 4.5–5.6 mm long, barbellate, white. Chromosome number: unknown.

Distribution and habitat.—Chile (Antofagasta). Until now, S. toconaoensis sp. nov. is only known from the southern part of La Pacana hills, located in El Loa Province. It grows in extremely arid screes from the desertic ‘puna’ ecoregion, near the vegetation limit at elevations between 4800 and 5000 m a.s.l. (Fig. 2). The remarkably few species observed thriving in the same habitat were Menonvillea virens (Phil.) Rollins (Cruciferae Juss.), Nototriche sp. (Malvaceae Juss.), Oriastrum polymallum Phil. (Compositae), and S. puchei Phil. (Compositae).

Phenology.—Collected in bloom in March.

Etymology.—The epithet refers to the community of Toconao, whose municipality encompasses the mountains where the plant was collected. The toponym Toconao comes from the extinct language Kunza (or ‘atacameño’) and it means stony place (‘tocknar’ being stone, and ‘ao’, place).

Discussion.—This species might be confused with S. algens, S. altoandinus, and S. cremnicola. Indeed, the single collection of the new taxonomic entity that was studied during the herbarium studies was identified as S. algens (CONC 139358). Although this latter species has a wide distribution and is quite variable, the characters regarding the leaf lamina, stems, and the achenes are useful for a proper identification. Senecio algens has the leaf lamina narrower (2–5 mm vs. 3.6–7 mm) and plane (vs. distally undulate or strongly recurved). It develops epigeous stems, rather elongated that lie on the ground. In contrast, S. toconaoensis sp. nov. has vertical hypogeous stems arising from the rhizome, which usually bear remnants of old leaves and are plainly white; at the surface the leaves grow clasped on the ground conferring a rosette-like habit. The achene indumentum is an unequivocal character to discriminate them from each other (glabrous in S. algens vs. long-pilose in S. toconaoensis sp. nov.).

Senecio altoandinus differs from the new species in the achene indumentum (papillose-pubescent vs. long-pilose), the more conspicuous denticulation of the leaves, and the epigeous prostrate woody stems. It is only known from a few collections made in the Humahuaca range (Jujuy, Argentina).

The leaves of S. cremnicola also slightly resembles those of the new species, however, it has glabrous achenes (vs. long-pilose) and 18–20 involucral bracts (vs. 13). It is considered an endemic species to La Rioja Province in Argentina (Freire & al. 2014).

ACKNOWLEDGEMENTSTOP

We are very grateful to the curators and staff of the herbaria mentioned in the text. This work has been funded by FONDECYT from Chile by means of a postdoctoral fellowship of the first author (project Nº 3170270).

REFERENCESTOP