Baccharis rectialata Valt., Bonif., G.Heiden & Marchesi, 2021

Valtierra, María Victoria, Marchesi, Eduardo, Heiden, Gustavo & Bonifacino, José M., 2021, Baccharis rectialata (Compositae: Astereae): a new species of carqueja from Uruguay, Phytotaxa 478 (2), pp. 253-260 : 257-259

Baccharis rectialata Valt., Bonif., G.Heiden & Marchesi , sp. nov. ( Figs. 1–3 )

Type:— URUGUAY. Treinta y Tres: Quebrada de los Cuervos , matorral en ladera alta rocosa, [32º55’4.36’’S, 54º 27’23.59’ W], 5 April 2017 , pistillate, V. Valtierra et al. 320 (Holotype: MVFA!, isotype: ECT!) .

Subshrubs 40 to 75 cm tall, profusely branched from the base, stems erect, minutely pubescent, grayish-green, surface glutinous, 3-winged, wings 0.7–6.8 × 0.15–0.35 cm, half-oblong (sometimes half-elliptic to half-ovate), margins straight or barely sinuous. Leaves reduced, alternate, spiral, sessile, 0.6–1.3 × 0.7–1.5 mm, triangular, base truncate, apex acute-attenuate, puberulous, glandular, margins entire. Capitula sessile, solitary or in clusters of 2 or 3 capitula, clusters arranged in pseudospikes 5–7.5 cm long, on terminal and lateral branches. Staminate capitula with involucres 3.5–4 × 3–3.7 mm, cylindrical, phyllaries in 5 to 6 series; outer phyllaries 1.2–1.5 × 1–1.3 mm, ovate, base truncate, apex acute, herbaceous, glandulous to resinous, minutely pubescent near to the central vein, margins ciliate, hyalinemembranaceous; inner phyllaries 3.8–4.1 × 0.6–0.8 mm, elliptic to obovate, base truncate, apex acute, herbaceous, minutely pubescent along the central vein towards the apex, margins ciliate at the apex, hyaline-membranaceous. Receptacles flat, fimbriolate. Florets 27 to 30, monoclinous, functionally staminate; corollas tubulose, white, 5-lobed, tube 1.8–2.3 mm long, cylindrical, slightly broadening towards the apex, lobes 1.5–1.8 mm long, triangular to narrowly elliptic, apex acute; anthers 1.1–1.2 mm long, base round, connective appendix 0.25–0.3 × 0.15–0.2 mm, ovate, apex acute; styles 4–4.9 mm long, style branches ca. 0.3 mm long, commonly fused, collector trichomes extending over ca. 1 mm of style distal part, stylopodium present, nectary disc 0.4 mm high, ovary 0.2–0.3 mm long, rudimentary. Pappus 3.1–3.9 mm long, bristles 16 to 23, scabrid, frizzy and slightly flattened towards the apex, fused at the base, arranged in 1 series. Pistillate capitula with involucres 4.5–5.5 × 2.5–3.5 mm, cylindrical to urceolate, phyllaries in 5 to 7 series; outer phyllaries 1.4–1.6 × 1–1.1 mm, ovate, base truncate, apex acute, herbaceous, pubescent, resinous and glandulous, margins ciliate, hyaline-membranaceous; inner phyllaries 4–4.8 × 0.4–0.7 mm, narrowly elliptic to linear, base truncate, apex acute, herbaceous, pubescent towards the apex, margins entire at the base and ciliate towards the apex, hyaline-membranaceous. Receptacles flat to slightly convex, fimbriolate. Florets 27 to 95, diclinous, pistillate; corollas filiform, 2.4–3.4 mm long, white, limb ca. 0.3 mm long, 3-lobed, lobes obtuse, unequal; styles 3.5–3.7 mm long, style branches 0.5–0.6 mm long, narrowly elliptic, apex acute, stylopodium present. Cypselae 1–1.6 mm long, obconic, terete, 12–15-ribbed, surface covered with micropapillae, small carpopodium present. Pappus 2.8–4.7 mm long, bristles 12 to 25, scabrid, slightly thinner towards the apex, fused at the base, arranged in 1 series, persistent.

Etymology:—The specific epithet refers to a defining feature of the new species, the nature of the wings which are all straight, with just barely sinuous margins.

Distribution and habitat:—In Uruguay, Baccharis rectialata has only been collected in the departments of Cerro Largo, Durazno, and Treinta y Tres ( Fig. 3 ), where it grows in rocky grasslands at 150–250 m asl. The habitat includes rocky grasslands often associated with scrub largely dominated by Baccharis dracunculifolia , Radlkoferotoma cistifolium (Compositae) , and Dodonaea viscosa (Sapindaceae) . According to Lezama et al. (2019), the new species (identified in their paper as Baccharis crispa Sprengel(1826:466)) occurs in sparsely-vegetated grasslands characterized by mesoxerophytic species developing on shallow or very shallow soils. According to Lezama et al. (2019), these communities are distinctive among several other grasslands hillside communities because of the presence of Oxalis conorrhiza (Oxalidaceae) , Chascolytrum erectum (Poaceae) , Baccharis rectialata and Baccharis ochracea . The new species seems to have a preference for rocky outcrops, although there is no evident geological correlation as we have found it in areas that vary from tectonically thrusted slabs including impure limestones (calc-phyllites), quartzites and low grade phyllites (Hartmann et al. 2001), medium grade biotite-rich granitic gneisses ( Bossi et al. 1998), highly cemented or lithified sandstones and conglomerates escarpments ( Ferrando & Andreis 1982; Caorsi & Goñi 1958) or generic granitic outcrops (Hartmann et al. 2001).

Phenology: —Flowering from February to May, fruiting from June to August.

Conservation assessment:— Baccharis rectialata was categorized as Endangered ( EN) in the AOO analysis. Only five scattered populations of this species have been found, associated with rocky grasslands developing on shallow soils. Only one of these populations occurs in a conservation area, the “Paisaje protegido Quebrada de los Cuervos” protected area, in Treinta y Tres, a department in eastern Uruguay ( Fig. 3 ). The other populations that were identified occur in the areas where forestry with exotic species has significantly intensified in recent years .

Taxonomic comments:— Baccharis rectialata is morphologically similar to B. trimera ( Lessing 1831: 141) Candolle (1836: 425) and B. crispa , inhabiting similar habitats or, as in the case of B. trimera , co-occurring with it. These three species share subshrubby habit, 3-winged stems profusely branched from the base, reduced leaves, and capitula arranged in glomerules along the terminal parts of main and lateral branches. However, B. rectialata differs from B. trimera in its narrower wings and a shorter capitulescence and from B. crispa in its straight wing margins, shorter involucres and a shorter pappus in staminate capitula (see Table I).

The new species also resembles Baccharis genistelloides ( Lamarck 1786: 93) Persoon (1807: 425) , a species distributed along the Andes, from Colombia to northern Chile, in open grasslands at 3300–4800 m asl. Besides its clear ecological differences; Baccharis rectialata differs from B. genistelloides in its shorter involucre in staminate capitula (3.5–4 vs. 4.5–7.5 mm long), staminate florets with a shorter pappus (3.1–3.9 vs. 4.3–6.5 mm long), pistillate florets with a shorter pappus (2.8–4.7 vs. 5.3–10.5 mm long), shorter pistillate corollas (2.4–3.4 vs. 3.5–6.8 mm long), fewer pappus elements in pistillate florets (12–25 vs. 28–56), and in the number of pappus series in pistillate florets (one vs. several).

Additional specimens examined (paratypes):— URUGUAY. Cerro Largo: Arroyo de la Tigra, cerca de Cerro de las Cuentas, [32°36’35.77”S, 54°34’30.63”W], 2 March 1972, staminate, O . Del Puerto ( MVFA 11103 !). Establecimiento Peñarrosa, Al Norte de Arévalo, 10 km al Sur de Paso Pereira , 32º31’52.95’’S, 55º10’42.52’’ W, 10 June 2016, pistillate, C . Brussa & M. Alvarez ( MVJB 29922 !) . Durazno: Ruta 6 km 199, [33°19’20.83”S, 55°35’32.85”W], 23 February 1994, pistillate, R . Brescia ( MVFA 23041 !) . Treinta y Tres: Estancia predios de forestación, 33º0’16.79’ ’ S , 54º13’9.09’’ W, 16 March 2017, staminate, C . Pérez et al. 102 ( MVFA!); 33º0’16.79’’S, 54º13’9.09’’ W, 16 March 2017, pistillate, C . Pérez et al. 103 ( MVFA!). Quebrada de los Cuervos, 32º55’4.36’’S, 54º27’23.59’’W, 5 April 2017, staminate, V . Valtierra et al. 321 (MVFA!).

TABLE I. Morphological comparison between Baccharis rectialata and closely related species occurring in Uruguay. Character states of B. crispa and B. trimera clearly contrasting with those observed in B. rectialata are highlighted in boldface.

Figures

FIGURE 1. Baccharis rectialata. A. Habit. B. Leaf. C. Phyllaries from staminate capitulum (left to right, outer to inner phyllaries). D. Staminate capitulum. E. Detail of fimbriate receptacle. F. Phyllaries from pistillate capitulum (left to right, outer to inner phyllaries). G. Pistillate capitulum. H. Pistillate floret corolla. I. Pistillate floret style. J. Staminate floret corolla. K. Staminate floret style. L. Cypselae and pappus of a pistillate floret. (V. Valtierra et al. 320, 321, MVFA and C. Brussa & M. Alvarez 29922, MVJB). Drawn by Valtierra & Bonifacino.

FIGURE 2. Baccharis rectialata. A. Habitat in grasslands in Quebrada de los Cuervos, Treinta y Tres, Uruguay. B. Habit. C. Close-up of wings; notice wing’s straight and narrow nature and rough texture. D. Capitulescence of pistillate individual. E. Capitulescence of staminate individual. F. Close-up of staminate capitulum. G. Close-up of pistillate capitulum.

FIGURE 3. Geographic distribution of Baccharis rectialata (Asteraceae).