Gutierrezia Lag. is an American genus, with disjunct distribution in North and South America. The species inhabits xerophytic or halophytic areas in the center-west of the United States and south of Mexico in North America where 18 species were recognised by Nesom (2006). It reappears in southern South America with ca. 13 species, of which one inhabits in Bolivia and has been collected in La Paz and Santa Cruz provinces (Solbrig, 1966); and six were recognised in Chile where they inhabit in the regions Metropolitana, I, II, III, IV, V, VI, XI and XII (Zuloaga et al., 2008). In Argentina, according to Zuloaga & Morrone (1999) and Zuloaga et al. (2008), the genus Gutierrezia grows from Jujuy to Territorio Nacional de Tierra del Fuego and is represented by eight species of which six are endemic. Recently Ratto & Bartoli (2014) described a new species from Mendoza, bringing to nine the species of Argentina with seven of these being endemic.

During the revision of South American species of the genus Gutierrezia we found some unusual herbarium specimens from the provinces of Jujuy and Salta that appeared to be different from other species of Gutierrezia that grow in these provinces—G. repens Griseb. and G. mandonii (Sch. Bip.) Solbrig. This prompted the first author (F. Ratto) to make a field trip so as to find other specimens in January 2014. He confirmed in the field that the plants appeared to be most allied to Gutierrezia mandonii by having xylopodium with numerous stems, similar leaf shape, and yellow ray flowers, but different in having erect and rigid stems (vs. decumbent and herbaceous), erect leaves (vs. patent), and smaller heads.

Upon closer examination we confirmed the differences mentioned above and we determined that the specimens represented a new species, Gutierrezia tortosae Ratto & Adr. Bartoli which is described here.

Gutierrezia tortosae Ratto & Adr. Bartoli, sp. nov.(Fig. 1).

Gutierrezia tortosae is characterised by having xylopodium, numerous, rigid and erect stems and erect leaves; and differs by these characters from G. mandonii, which is characterised by its decumbent and herbaceous stems, patent leaves and larger heads.

Type: Argentina, Jujuy: Dept. Susques, Angosto de las Burras, 3534 m, 06.02.2014, F. Ratto 47 et al. (hololotype: BAA; isotypes: BAA, BC, CTES, SI).

Subshrubs 5–25(35) cm, with xylopodium. Stems numerous, erect, rigid, ribbed, glandular, not or few ramified, leafy at the base and loosely foliaceous to the apex. Leaves subcoriaceus, erect, sessile, irregularly toothed at margin, linear-elliptic, with stipitate glandular trichomes and sessile glandular trichomes in pits on both blade surfaces, 5–15 × 1–1.5 mm, acute. Heads radiate, heterogamous, pedunculate, 1–1.5 cm diam., arranged in corymbiform cymes at stem apex; peduncles 5–30 mm, with 1 or 2 linear-elliptic bracts 2–3 mm long. Involucre campanulate, resinous, 4–6 × 3–5 mm. Receptacle flat or slightly convex, naked, pitted, pilose. Phyllaries in 3 graduated series; outer phyllaries oblong, glandular, acuminate, inner phyllaries narrowly obovate, apiculate. Ray florets 6 to 8, pistillate, with lamina yellow, narrowly obovate, 6–7 mm long; style with branches linear-elliptic, apex acute, papilose. Disk florets 12 to 15, perfect, with corolla yellowish, 3–4 mm long, tubular, with an abruptly ampliate throat, 5-lobed. Anthers rounded at the base; apex of connective ovate to ovate elliptic; style branches elliptic, acute, with sweeping papillose trichomes on the outer side. Achenes grey, obovoid-turbinate, densely sericeus; pappus of 10–15 linear-elliptic erose-margined scales, ca. 1 mm long in ray florets and 1–1.5 mm long in disk florets.

Etymology: Gutierrezia tortosae was named in honour of our Professor Roberto Daniel Tortosa, an Argentine botanist who worked extensively on Rhamnaceae and Asteraceae.

Additional specimens examined: Argentina, Jujuy: Depto. Humahuaca, Esquinas Blancas, 13.02.1921, A. Castellanos 24 (BA); Depto. Humahuaca, Mina Aguilar, 12.01.1948, A. L. Cabrera 9186 (BAB); Depto. Humahuaca, Cerro Aguilar, Espinazo del Diablo, 22.02.1953, J. Hunziker & O. Caso 6158 (BAB); Depto. Humahuaca, Tres Cruces, 20.02.1959, H. A. Fabris & J. M. Machionni 1801 (LP); Depto. Humahuaca, Puente del Diablo, 5 km al sur de Tres Cruces, 31.09.1970, H. A. Fabris & F. O. Zuloaga (LP); Depto. Humahuaca, desde El Aguilar hasta Agua Blanca, n.v. “canchalagua”, 01.1988, J. Fernández 3005 (BA); Depto. Humahuaca, Tres Cruces, 07.02.2014, Ratto et al. 111 (BAA); Depto. Humahuaca, El Aguilar, 11.02.2014, Ratto et al. 143 (BAA); Depto. Susques, en las afueras de Susques, 07.02.2014, Ratto et al. 64 (BAA); Depto. Tumbaya, Volcán, 08.02.1960, T. Meyer 21796 (LIL); Depto. Tumbaya, Abra de los Pives, 10.02.1966, J. G. Hawkins & K. Hahn 3795 (LP); Depto. Tumbaya, camino de El Angosto a Chaña, 26.02.1972, A. L. Cabrera et al. 22496 (LP); Depto. Tumbaya, Quebrada de Humahuaca, Volcán, 14.04.1988, L. Novara 7929 (MCNS); Depto. Tumbaya, Cuesta de Lipán, 21.02.1993, T. F. Stuessy & J. M. Morles 12992 (LP); Depto. Tumbaya, serranías frente a El Colorado, 07.04.2004, J. A. Tolaba et al. 3583 (MCNS); Depto. Tumbaya, Cuesta de Lipán, 07.02.2014, Ratto et al. 85 (BAA); Depto. Tumbaya, Salinas Grandes, 07.02.2014, Ratto et al. 90 (BAA). Salta: Depto. Iruya, alrededores del pueblo de Iruya, 13.03.1988, J. A. Hurrel 679 (LP); Depto. Iruya, San Isidro, Pantipampa, 24.03.1994, M. Quiroga Mendiola 1391 (MCNS); Depto. La Poma, Quebrada de Cobres, 12.03.1945, A. L. Cabrera 8723 (LP); Depto. La Poma, Cobres, Sierras de Rangel, 06.02.2014, Ratto et al. 35, 41 y 42 (BAA); Depto. Rosario de Lerma, Santa Rosa de Tastil, 09.02.1946, A. L. Cabrera 9020 (LP); Depto. Rosario de Lerma, El Chañar, 24.01.1989, M. O. Arriaga et al. 557 (BA); Depto. Rosario de Lerma, Finca El Toro, 19.02.1995, S. López 1570 (MCNS); Depto. Rosario de Lerma, Santa Rosa de Tastil, 05.02.2014, Ratto et al. 11 (BAA); Depto. San Antonio de Los Cobres, Quebrada de Polvorillas, 11.02.1945, A. L. Cabrera 9631 (LP); Depto. San Antonio de Los Cobres, San Antonio de Los Cobres, camino a Salinas Grandes, 15.12.1946, A. Krapovickas 3175 (LIL).

Phenology: Gutierrezia tortosae flowers from January to July.

Distribution and habitat: Gutierrezia tortosae inhabits in the province of Jujuy, departments of Cochinoca, Humahuaca, Rinconada, Susques, Tilcara, Tumbaya, Valle Grande y Yavi, and in the province of Salta, departments of Iruya, La Poma, Los Andes, Rosario de Lerma and San Antonio de Los Cobres. This species grows on rocky slopes, at elevations ranged from 2000 to 4400 m and it is associated with xerophytic shrubsof the genera Fabiana, Baccharis, Junellia, and Senecio, and cacti of the genera Trichocereus, Opuntia, Parodia, and Lobivia (Figs. 2 and 3.

Common name: “canchalagua” in aboriginal language refers to a plant used to treat pain (Zardini, 1984).

Taxonomic position: two species of Gutierrezia were previously known in the Jujuy and Salta provinces: G. repens also grows in Catamarca and Tucumán provinces, and G. mandonii also inhabits in Tucumán Province and in the neighbouring country of Bolivia. Both species mentioned above and G. tortosae can be distinguished by features found in the following key.

1. Shrubs without xylopodium. Leaves elliptic, 3–4 mm wide. Heads 21-22 mm wide

........................................................................................................ G. repens

-. Shrubs with xylopodium. Leaves linear-elliptic, ≤ 2.5 mm wide. Heads ≤ 20 mm wide

........................................................................................................2

2. Stems erect and rigid. Leaves erect, 5–15 × 0.5–1.5 mm. Heads 10–15 mm wide

........................................................................................................ G. tortosae

-. Stems decumbent and herbaceous. Leaves patent, 15–25 × 1.5–2.5 mm. Heads 18–20 mm wide

........................................................................................................ G. mandonii