Chromolaena paraguariensis (Hieronymus) King & Robinson (1970c: 204)

Christ, Anderson Luiz & Ritter, Mara Rejane, 2019, A taxonomic study of Praxelinae (Asteraceae-Eupatorieae) in Rio Grande do Sul, Brazil, Phytotaxa 393 (2), pp. 141-197 : 178-180

2.11. Chromolaena paraguariensis (Hieronymus) King & Robinson (1970c: 204) .

Eupatorium paraguariense Hieronymus (1897: 752) . Eupatorium oxylepis subsp. paraguariense (Hieron.) Hassler (1916: 281) . Lectotype (designated by Freire & Ariza Espinar 2014b: 338):— PARAGUAY. Paraguari, 25 March 1875, B. Balansa 934 (G! [G00381897], isolectotypes BAF, BM! [BM000096323], S! [S10-20127], [S-R-2163]).

= Chromolaena angusticeps (Malme) King & Robinson (1981: 4) . Eupatorium angusticeps Malme (1931: 25) , syn. nov. Lectotype (designated here):— BRAZIL. Rio Grande do Sul: Porto Alegre, between Menino Deus and Cristal, 03 March 1902, G.O.A.N. Malme s.n. (S! [S10-19896], isolectotype S! [S-R-2095]). ( Fig. 20A–D ).

Subshrubs to shrubs, up to 1 m tall, erect, xylopodium present, branched only in capitulescence; stems puberulous to villose, eglandular, leafy until capitulescence. Leaves 2.3–3.6 × 0.9–1.3 cm, opposite, petiolate, 3-veined, leaf blade ovate to lanceolate, chartaceous, apex acute to acuminate, rarely obtuse, base cuneate to rounded, margins entire to sparsely serrate, adaxial surface strigose, eglandular, abaxial surface villose, glandular, margins ciliate, petioles 4.6–6.1 mm long, villose, eglandular. Primary capitulescences corymbose. Secondary capitulescences paniculate, axis puberulous to villose, eglandular, bracteate, bracts 0.8–3.7 × 0.2–1.3 cm, petioles 1.4–6.1 mm long, villose, eglandular. Capitula pedunculate, peduncles 0.5–2 cm long, puberulous, eglandular, involucres campanulate, rarely cylindrical, 7.9–9.3 × 2.9–4.5 mm, involucral bracts 31–41, 6–7-seriate; outer deltate to ovate, 1.2–2.9 × 0.7–1.4 mm, apex acute to cuneate, stramineous, ciliate, glabrous, eglandular, appressed, abaxial surface stramineous, 3–5-veined, glabrous, inner linear, 6.9–8.3 × 0.5–0.9 mm, apex acute to cuneate, stramineous, non-petaloid, ciliate or eciliate, glabrous, eglandular, appressed, abaxial surface stramineous, 3-veined, glabrous, receptacles epaleate. Florets 16–23, corollas 4.3–5.6 × 0.4–0.7 mm, lilac, lobes glabrous, glandular. Cypselas obconical, 2.9–4 × 0.4–0.8 mm, 5–7-ribbed, ribs glabrous to setuliferous, sinuses glabrous, eglandular, pappus setae ca. 29–36, white to stramineous, 4.9–6 mm long.

Distribution: — Argentina , Brazil and Paraguay. In Brazil, it is recorded only in Rio Grande do Sul. In Rio Grande do Sul, it occurs in the physiographic regions of Depressão Central and Serra do Sudeste ( Fig. 21 , triangles).

Habitat: —Grasslands in the Pampa biome, usually in shallow and poor soils or near rocky outcrops.

Phenology: —Flowers from the end of summer to the beginning of autumn, with a flowering peak in March and April.

Etymology: —The specific epithet is a reference to Paraguari, in Paraguay, where the type specimens was collected.

Comments: — Chromolaena paraguariensis is cited here for the first time for Rio Grande do Sul. This name is used to refer to a species previously treated as Chromolaena angusticeps . These two names were never considered synonyms prior to our study. Our reason for this synonymization is mostly due to a morphological continuum connecting the types of both specimes. Both share leaves ovate to lanceolate, in general with rounded base and entire margins, with villose indumentum in the stems and in the abaxial surface of the leaves. The type specimens also share the characteristic inner involucral bracts with acute to cuneate apices, a character unique to them among the Chromolaena of Rio Grande do Sul. They could be distinguished through the length of the internodes and the size of the leaves, characters found to be extremely plastic and notably variable in the examined specimens. Despite the existence of few specimens with intermediary morphology between the two type specimens, we did not find enough features to distinguish between these two species, and the analyzed material show a clear continuum of the features mentioned above connecting the type specimens of C. paraguariensis and C. angusticeps . In this manner, we disagree from Freire & Ariza Espinar (2014b), who consider C. paraguariensis as a synonym of C. pedunculosa .

Eupatorium angusticeps was described by Malme (1931) based on specimens collected in Porto Alegre, Rio Grande do Sul and was considered mostly restricted to the metropolitan area of this municipality, where most of its known specimens were collected. The species is characterized by its inner involucral bracts with acute apices, hence its name. According to Matzenbacher (1979), E. angusticeps was considered probably extinct in the wild, mostly due to the lack of collections of this species after the 1940s. Since the study of this author, several specimens were collected in other regions of Rio Grande do Sul and identified as E. angusticeps ; most of them, however, were misidentified specimens of C. pedunculosa . The most recent specimen belonging to this species collected in the state was Schaefer 313, deposited in SMDB and collected in the municipality of Santa Maria in 2015. We did not find any material of C. paraguariensis during our field trips, but we disagree with Matzenbacher (1979) since, apart the collection in SMDB, there are other few specimens of C. paraguariensis collected in the last 10 years in the state. This probably means that C. paraguariensis is a very rare species in Rio Grande do Sul and only seldom found by collectors, what explains its absence in the majority of the herbaria visited.

The most similar species to C. paraguariensis found in Rio Grande do Sul is C. pedunculosa . Both can be distinguished by the villose indumentum of the abaxial surface of the leaves of C. paraguariensis and by the characteristic involucre of this species, with inner involucral bracts always showing acute to cuneate apices. Chromolaena pedunculosa , in contrast, has inner involucral bracts with rounded to obtuse apices. Chromolaena paraguariensis also has xylopodia and shows a tendency of capitula with fewer florets, but this is not a general rule. The involucres and the indumentum of the leaves, however, are constant in the examined specimens, suggesting it is a strong diagnostic feature of this species.

Specimens examined: — BRAZIL: Rio Grande do Sul: Caçapava do Sul: BR-290, 14 April 2012, Pasini , E. 905 ( ICN). Porto Alegre: Cemitério, 03 March 1941, Emrich, K. s.n. ( PACA11924 ) ; Montserrat, 01 April 1942, Emrich , K. s.n. ( PACA10190 ) ; 11 April 1942, Augusto , I. s.n. ( ICN19061 ) ; Morro Santana [30°03’22,7’’S, 51°07’35,5’’W], 20 April 2007, Fernandes, A. C. & Ritter, M. R. s.n. ( ICN158471 ). Santa Maria: Morro Pedra do Lagarto , Distrito de Santo Antão , 03 February 2015, Schaefer, J. 313 ( SMDB). São Leopoldo: Feitoria, 18 March 1937, Dutra , J. 1547 ( ICN). Viamão: para Porto Alegre, 10 April 1950, Rambo, B. s.n. ( PACA46741 ) .

Figures

FIGURE 20A–D: Chromolaena paraguariensis. A. Fertile branch. B. Capitulum. C. Involucral bracts. D. Floret. E–I: Chromolaena pedunculosa. E. Fertile branch. F. Capitulum. G. Involucral bracts. H. Floret. I. Palea.

FIGURE 21: Distribution of C. paraguariensis (triangles), C. pedunculosa (circles) and C. rhinanthacea (diamond) in Rio Grande do Sul.