Gutierrezia chubutensis Ratto et Adr. Bartoli, 2016

Ratto, Francisco & Bartoli, Adriana, 2016, A new species of Gutierrezia (Asteraceae, Astereae, Solidagininae) from Argentinian Patagonia, Phytotaxa 266 (2), pp. 157-160 : 157-160

Gutierrezia chubutensis Ratto et Adr. Bartoli , sp. nov. ( Figs. 1 and 2 )

Type:— ARGENTINA. Chubut: Dept. Gaiman, Dique Florentino Ameghino , 43º 41.596 ʹ S, 66º 28.854 ʹ O, 172 m s. m., 17 January 2016, F. Ratto, D. Sbarra & M. Sorondo 14/2016 (holotype BAA; isotypes BAA, BC, SI) .

Resinous shrubs 30–55(60) cm. Stems numerous, erect and decumbent, rigid, ribbed, with stipitate glandular trichomes, ramified, leafy from base to apex. Leaves subcoriaceous, erect or at an acute angle, sessile, widely elliptic, with stipitate glandular trichomes and sessile glandular trichomes in pits on both blade surfaces, minutely toothed at margin, 25–50 × 3–6 mm, 1-nervate, acute. Heads radiate, heterogamous, sessile, 1–1.5 cm in diam., arranged in corymbiform cymes at stem apex; with 1 to 3 linear or linear-elliptic, retrorse bracts 3–7 mm long. Involucre terete or terete-turbinate, resinous, 7–9 × 2–4 mm. Receptacle flat or slightly convex, naked, pitted, pilose. Phyllaries in 3 graduate series, scarious at margin, outer phyllaries ovate, with sessile glandular trichomes, acuminate, inner phyllaries narrowly obovate, with sessile glandular trichomes, apiculate. Ray florets 7 to 9, pistillate, with corolla yellow, narrowly obovate, 6–7 mm long; style with branches linear-elliptic, acute, with short papilose trichomes on the outer side. Disk florets 7 to 9, perfect, with corolla yellow, 4 mm long, tubular, with an abruptly ampliate throat, shortely 5-lobed. Anthers rounded at base; apical appendage ovate to triangular, 0.5 mm long; style branches elliptic, obtuse, with short papillose trichomes on outer side. Achenes grey, terete-turbinate, densely sericeous, 1–2 mm long; pappus of 8–14 linear-elliptic erose-margined scales, ca. 1–2 mm long in ray florets and 2–3 mm long in disk florets.

Similar taxa:— Gutierrezia chubutensis is characterized by being more than 50 cm tall, having subcoriaceus leaves, erect or at an acute angle, widely elliptic, 25–50 × 3–6 mm, numerous heads, and the shape of the involucres terete or terete-turbinate. Its related species, with which it shares the yellow colour of florets, differ as follows: G. baccharoides in the rhizomatous habit, solitary heads and the hemispheric involucre, and G. ameghinoi , for which it can be mistaken in the juvenile stages due to the similarity of some characters such as the shape of the involucre and leaves, in the cushion habit at adult stages (while G. chubutensis is a shrub). Both species, G. baccharoides and G. ameghinoi , also differ in being less than 25 cm tall.

Distribution and habitat: — Gutierrezia chubutensis is exclusively known from the province of Chubut, Argentina. It occurs in the Patagonian phytogeographic province, Patagonian Central District ( Cabrera 1971b). This species grows on rocky slopes ( Fig. 2A ) at elevations near 200 m a.s.l. and is associated with xerophytic shrubs from the genera Colliguaja , Grindelia , Larrea , Nassauvia and grasses like Festuca , Poa and Stipa .

Etymology: —The specific epithet refers to the Argentine province where it has been found.

Phenology: — Gutierrezia chubutensis has been collected in flower from November to January.

Additional examined specimens (paratypes): — ARGENTINA. Chubut: Florentino Ameghino, RP 25, 130 km W Trelew , 25 November 1978, H. Cordo & Ferrer 79-A-34 ( SI) ; Gaiman, Dique Florentino Ameghino , 17 January 2016, 172 m s. m., F. Ratto, D. Sbarra & M. Sorondo 13/2016 ( BAA) .

Note:— Ratto & Bartoli (2015) cited a specimen under the name G. ameghinoi that should be considered G. chubutensis due to the size of its involucre.

Taxonomic position: —The four species previously reported from Patagonia and the new species described in this paper can be differentiated by the following key.

1. Heads with white corollas; involucre bell-shaped..............................................................................................................................2

- Heads with yellow corollas; other shape of involucre........................................................................................................................3

2. Leaves elliptic; heads numerous in dense corymbiform inflorescences ........................................................................... G. solbrigii

- Leaves linear or linear elliptic; heads solitary or grouped by 3 or 4 in lax inflorescences ................................................. G. gilliesii

3. Heads solitary; involucre hemispheric; habit rhizomatous ....................................................................................... G. baccharoides

- Heads grouped into inflorescences; involucre terete or terete-turbinate; habit non-rhizomatous......................................................4

4. Cushion subshrubs 10–20(25) cm tall; involucre 6 × 4 mm; leaves linear-elliptic with obtuse apex............................ G. ameghinoi

- Erect shrubs 30–55 (60) cm; involucre 7–9 × 4 mm; leaves elliptic with acute apex.................................................. G. chubutensis

Figures

FIGURE 1. Gutierrezia chubutensis (Asteraceae). A. plant, B. cauline leaf, C. head, D. outer phyllary, E. middle phyllary, F. inner phyllary, G. ray floret with fruit and pappus, H. disk floret with fruit and pappus.

FIGURE 2. Gutierrezia chubutensis (Asteraceae). A. individual on rocky slopes, B. inflorescence detail, C. population on rocky slopes associated with xerophytic shrubs.All photos were taken in Dique Florentino Ameghino, Chubut Province by M. Sorondo.