Senecio festucoides J.Calvo & A.Moreira, 2020

Calvo, Joel & Moreira-Munoz, Andres, 2020, Senecio festucoides (Senecioneae, Compositae), a new species from northern Chile, PhytoKeys 149, pp. 89-98 : 89

Senecio festucoides J.Calvo & A.Moreira sp. nov. Figs 1 , 2A-C

Diagnosis.

The new species mainly differs from its morphologically closest species S. scorzonerifolius in the yellow corollas, yellowish anthers and style branches, glabrous leaves, long peduncles with 1-3 linear bracts, and by having (17-)21 involucral bracts.

Type.

Chile. Antofagasta: San Pedro de Atacama, Machuca, 4 km antes de la entrada a los géisers del Tatio, 22°23'S, 68°1'W, 4375 m, 27 Feb 2020, fl. and fr., J. Calvo 8120 (holotype: SGO; isotypes: CONC, MA, US).

Perennial not self-supporting herb, rarely decumbent, with a thin rhizome. Stem 15-25 cm tall, 1.8-2.5 mm wide, rather terete, branched in the lower part, weak. Leaves alternate, narrowly linear (leaf width/length ratio 0.01-0.03), 41-78 mm long, 0.9-1.2 mm wide, apex acute, base sessile (uniform in width), margin entire and flat (rarely with a few distant teeth), elliptic in cross section (rather flat when dried), glabrous on both surfaces, yellowish green, with a graminoid appearance. Capitula discoid, solitary, terminal, pedunculate; peduncle 5-6 cm long, glabrous, with 1-3 linear bracts up to 6 mm long. Involucre 12-14 mm long, 8-10 mm wide (in living plants); involucral bracts (17-)21, oblong-lanceolate, 10-11 mm long, 1.2-2 mm wide, acute to attenuate at the apex, smooth, glabrous, blackish-tipped; supplementary bracts (3-) 5-8, linear, 3.9-6 mm long, 0.9-1.1 mm wide, smooth, a third as long as the involucral bracts, glabrous, blackish-tipped. Florets 85-95, hermaphrodite; corolla tubular, 7.5-8.8 mm long, 0.5-0.7 mm wide, 5-lobed, the limb usually longer than the tube, yellow. Anthers yellowish; anther appendages 2-3 times longer than wide, ca. 0.5 × 0.2 mm; anther bases auriculate; filament collar balusterform. Style branches truncate with a crown of sweeping hairs, yellowish. Achenes 4.2-5.3 mm long, 0.9-1 mm wide, 8-10 ribbed, minutely papillose, brownish; pappus 7.5-9 mm long, barbellate, whitish. Chromosome number: unknown.

Distribution and habitat.

Chile (Antofagasta, Tarapacá). Considering the proximity of both populations to the Bolivian territory and the presence of similar environments across the border, its presence in this latter country is likely. It thrives in exposed grassy slopes and plains of the desertic Puna ecoregion, between elevations of 4325-4550 m (Fig. 3 ).

Senecio festucoides grows amongst tufts of Festuca chrysophylla Phil. ( Poaceae ) [= F. orthophylla Pilg. according to Ospina et al. (2013)] (Fig. 1F ); indeed, the tufts provide support for S. festucoides stems, which are not self-supporting. If the new species is not in flower, it is difficult to detect because its leaves are easily confused with those of Festuca (Fig. 1C, D ). The following species were observed in the same habitat: Astragalus minimus Vogel ( Leguminosae ), Mulinum crassifolium Phil. ( Apiaceae ), Parastrephia quadrangularis (Meyen) Cabrera ( Compositae ), Pycnophyllum tetrastichum J. Rémy ( Caryophyllaceae ), Senecio scorzonerifolius , and Werneria glaberrima Phil. ( Compositae ).

Phenology.

Collected in flower from January to March.

Etymology.

The epithet festucoides refers to the conspicuous resemblance of the leaves to those of Festuca chrysophylla , amongst which the new species grows.

Conservation status.

Thus far, the new species is only known from two locations and has an extent of occurrence of ca. 2000 km2. This would fit the category Endangered (EN) according to the B1a criteria ( IUCN 2012). However, it is preliminarily assigned to the category Near Threatened (NT) considering that further data on distribution and population dynamics are essential to firmly establish that the species is facing a very high risk of extinction in the wild.

Discussion.

Senecio festucoides shows morphological affinities with the sympatric species S. scorzonerifolius (Fig. 3 ), which is known from southern Peru, western Bolivia, northwestern Argentina, and northern Chile. Although these species have a similar appearance, they belong to different subgroups within the discoid caespitose Andean Senecio , i.e. the new species is a member of the subgroup displaying yellow corollas and yellowish anthers and style branches whereas S. scorzonerifolius belongs to the subgroup with white corollas and blackish anthers and style branches (Fig. 2B ). They also differ in leaf indumentum (glabrous in S. festucoides vs. densely to barely arachnoid, rarely almost glabrous in S. scorzonerifolius ), peduncle bract type (linear bracts up to 6 mm long in S. festucoides vs. leaf-like bracts up to 30 mm long that gradually decrease in size upwards in S. scorzonerifolius ; see Fig. 2A ), involucral bract number and length ((17-)21, 10-11 mm in S. festucoides vs. (9)13-15, 8-9 mm in S. scorzonerifolius ), supplementary bract length (3.9-6 mm, a third as long as the involucral bracts in S. festucoides vs. 6-8 mm, a half to two thirds as long as the involucral bracts in S. scorzonerifolius ; see Fig. 2A ), and achene indumentum (minutely papillose in S. festucoides vs. papillose in S. festucoides ). Moreover, S. festucoides has longer stems and does not develop crowded tufts as S. scorzonerifolius usually does (Fig. 2C, D ). In living plants, their leaf color is also different (yellowish green in S. festucoides vs. dark green in S. scorzonerifolius ; see Fig. 2C ).

The leaf shape of the new species might lead any botanist to confuse it with S. bolivarianus Cuatrec., a species endemic to Peru known from Ancash to Moquegua ( Beltrán and Roque 2015). They can be readily differentiated by the abaxial leaf surface (densely silky-villous except for the midrib in S. bolivarianus vs. glabrous in S. festucoides ), leaf margin (revolute in S. bolivarianus vs. flat in S. festucoides ), leaf base (broadened into a sheath-like base that bears long silky trichomes in S. bolivarianus vs. uniform in width and glabrous in S. festucoides ), and number of supplementary bracts (12-16 in S. bolivarianus vs. (3-)5-8 in S. festucoides ). Moreover, S. bolivarianus has linear to narrowly lanceolate leaves rather than narrowly linear as in S. festucoides .

It should be noted that S. festucoides is characterized by its narrowly linear, entire leaves but we also observed a few specimens displaying both entire and distantly dentate leaves. Such leaf dimorphism is usual in other related species such as S. digitatus Phil. ( Calvo et al. 2019) and S. scorzonerifolius ( Cabrera 1985; Fig. 2D ).

Additional specimens examined.

Senecio festucoides (paratypes). Chile. Antofagasta: Loa, San Pedro de Atacama, Machuca-El Tatio, ca. 6.2 km al S de El Tatio, 22°23'S, 68°1'W, 5 Mar 2019, J. Calvo 7925 (SGO); Tarapacá: Collahuasi, quebrada San Nicolás, 20°59'S, 68°39'W, 22 Jan 1994, S. Teillier 3296 (SGO).

Senecio scorzonerifolius . Bolivia. Oruro: Sabaya, parte alta del Pumire, 19°0'S, 68°25'W, 7 Feb 2019, J. Calvo 7838 (LPB); cerro Cabaray [Carabaya], faldeos, 19°9'S, 68°42'W, 23 Mar 1982, C. Villagrán & M.T.K. Arroyo 4209 (CONC); Potosí: cordillera Kari Kari, aprox. 3.3 km arriba de la laguna San Sebastián, 19°36'S, 65°41'W, 13 Feb 2019, J. Calvo & M. Zárate 7868 (BOLV); Frías, between laguna Lobato and laguna Chalvira, cordillera Kari Kari, 19°38'S, 65°42'W, 6 Mar 1999, J.R.I. Wood 14596 (K). Chile. Antofagasta: Loa, San Pedro de Atacama, Toconao, quebrada Aguas Blancas, 23°17'S, 67°42'W, 22 Feb 2001, M. Ackermann 93 (SGO); cerro Nevados de Poquis, ladera SO, 23°4'S, 67°4'W, 9 Apr 1997, M.T.K. Arroyo, L. Cavieres & A. Humaña 97367 (CONC); cerro Miñiques, 23°46'S, 67°46'W, 9 Mar 1993, G. Baumann 192 (CONC); quebrada al lado sur del volcán Lascar, 23°23'S, 67°48'W, 14 Feb 1994, G. Baumann 351 (CONC); Machuca-El Tatio, ca. 4.2 km al S de El Tatio, 22°22'S, 68°1'W, 5 Mar 2019, J. Calvo 7923 (CONC, SGO); Machuca, 4.1 km antes de la entrada a los géisers del Tatio, 22°23'S, 68°1'W, 27 Feb 2020, J. Calvo 8114 (SGO); Toconao, 57 km pass, 23°36'S, 67°51'W, 27 Jan 1971, H. Ellenberg 4230 (US); inter Aguas Calientes et Socaire, 23°46'S, 67°47'W, 1 Feb 1885, F. Philippi s.n. (LP, SGO; type material of the later heterotypic synonym Senecio armeriifolius Phil.); quebrada Tatio, 15 Feb 1943, E. Pisano & J. Venturelli 1879 (CONC, SGO); laguna de Miñique, entre los cerros Miñique y Miscanti, 23°46'S, 67°47'W, 24 Feb 1943, E. Pisano & J. Venturelli 1968 (SGO); trayecto entre Talabre y laguna Lejía, 23°25'S, 67°47'W, 2 Apr 1998, C. Villagrán, F. Hinojosa & C. Latorre 9315 (CONC); Taltal, cord. volcán Llullaillaco, 24°38'S, 68°34'W, Feb 1926, E. Werdermann 1029 (CONC); Arica-Parinacota: camino entre Putre y Pacollo, 18°11'S, 69°31'W, 17 Apr 1984, M.T.K. Arroyo 84-887 (CONC); rt. A23 from rt. 11 NW to Tacora, near intersection of rt. A23 & A125, slopes of Co. de Tarapacá, 17.6 km from rt. 11, 18°4'S, 69°32'W, 7 Mar 2014, V.A. Funk, M. Diazgranados & J.M. Bonifacino 13111 (US); camino de Putre a Chucuyo, km 8, 18°10'S, 69°30'W, 12 Feb 1964, C. Marticorena, O. Matthei & M. Quezada 179 (CONC); lagunas de Cotacotani, 18°12'S, 69°13'W, 13 Feb 1964, C. Marticorena, O. Matthei & M. Quezada 236 (CONC); cerro Guane-Guane, ladera W, 18°10'S, 69°16'W, 18 Mar 2015, A. Moreira-Muñoz & F. Luebert 2423 (SGO); portezuelo de Putre, laderas de los cerros, 18°12'S, 69°20'W, 6 May 1972, M. Ricardi, E. Weldt & M. Quezada 237 (CONC); Parinacota, 18°12'S, 69°16'W, 29 Mar 1961, M. Ricardi, C. Marticorena & O. Matthei 291 (CONC); cerros de Parinacota, 28 Feb 1948, F. Sudzuki 486 (SGO); Caquena, 18°3'S, 69°12'W, 1 Feb 1970, O. Zöllner 5321 (CONC); Tarapacá: Iquique, Collahuasi (Ujina), 20°58'S, 68°37'W, 24 Mar 1992, B.J. Ruthsatz 8429 (CONC). Peru. Moquegua: minera Quellaveco, 17°6'S, 70°36'W, 27 Jan 1971, ESCO 7240 (US).

Figures

Figure 1. Senecio festucoides A involucral bracts and florets B supplementary bracts C, D capitula E habit F habitat (black arrow shows a capitulum amongst a tuft of Festuca chrysophylla). Pictures by Joel Calvo at the locus classicus (between Machuca and El Tatio, San Pedro de Atacama, Antofagasta, Chile).

Figure 2. A-C Senecio festucoides (left hand; Calvo 8120) and S. scorzonerifolius (right hand; Calvo 8114) D Senecio scorzonerifolius (Calvo 8114) A capitula (white arrows show the supplementary bracts; black arrows show the peduncle bracts) B florets C habit D leaves and capitula (notice leaf dimorphism). Pictures by Joel Calvo.

Figure 3. Distribution area of Senecio festucoides (red cross) and S. scorzonerifolius (open circle) in Chile. Abbreviations: ARG (Argentina), BOL (Bolivia), CH (Chile), and PER (Peru).