Chromolaena squarrulosa (Hooker & Arnott) King & Robinson (1970c: 206)

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 : 187-189

2.15. Chromolaena squarrulosa (Hooker & Arnott) King & Robinson (1970c: 206) .

Eupatorium squarrulosum Hooker & Arnott (1836: 239) . Lectotype (designated by Freire & Ariza Espinar 2014b: 339):— BRAZIL. Rio Grande do Sul, s.d., J. Tweedie s.n. (E! [E00385505]).

= Eupatorium liatrideum Candolle (1836: 142) . Type:— BRAZIL. Rio Grande do Sul, 1833, C. Gaudichaud 756 (holotype P! [P02407975]).

= Eupatorium liatrideum var. subcanum Candolle (1836: 142) . Type:— BRAZIL. Rio Grande do Sul, 1833, C. Gaudichaud 751 (holotype P! [P02407978]).

= Eupatorium caaguazuense var. nervosum Chodat (1902: 306) . Lectotype (designated by Freire & Ariza Espinar 2014b: 339):— PARAGUAY. Carimbatay, September 1898 –1899, E. Hassler 4567 (G! [G00381849], isolectotype BM! [BM000096329]).

= Eupatorium ascendens var. parcisetosum Robinson (1923: 9) . Type:— BRAZIL. Rio Grande do Sul, s.d., A. de Saint-Hilaire 2761 (holotype P! [P00742307]). ( Fig. 25A–E , 28C–D ).

Subshrubs, up to 70 cm tall, decumbent, rarely erect, xylopodium present, branched only in capitulescence; stems strigose to tomentose, rarely glabrescent, glandular or eglandular, leafy until capitulescence or only in lower half, then aphyllous or near-aphyllous in upper half. Leaves 1.2–5.7 × 0.4–2.3 cm, opposite, petiolate, 3-veined, leaf blade orbicular to oblong, papyraceous to coriaceous, apex acute to rounded, base rounded to truncate, sometimes cuneate, margins crenate to serrate, adaxial surface glabrous to strigose, glandular or eglandular, abaxial surface glabrous to strigose, glandular, margins ciliate, petioles 1.3–6.5 mm long, puberulous, eglandular. Primary capitulescences corymbose. Secondary capitulescences corymbose or umbel-like; axis puberulous to tomentose, glandular, bracteate or ebracteate, bracts 0.8–2.5 × 02– 0.9 cm, petioles 1.5–2.7 mm long, puberulous, eglandular. Capitula long pedunculate, rarely sessile or subsessile, peduncles up to 3.7 cm long, puberulous to tomentose, glandular, involucres cylindrical to campanulae, 6.2–9 × 2.5–4.9 mm, involucral bracts 15–35, 5–7-seriate, outer orbicular to oblong, 2–3.7 × 1–2.6 mm, apex cuneate to obtuse, citrine, ciliate, tomentose, glandular or rarely eglandular, recurved to squarrose, abaxial surface stramineous to citrine, 3–5-veined, puberulous, inner linear, 5–7 x 0.8–1.4 mm, apex acute to acuminate, vinaceous, non-petaloid, ciliate, puberulous to tomentose, glandular or rarely eglandular, slightly recurved to recurved or rarely squarrose, abaxial surface vinaceous, 1–3-veined, glabrous to puberulous, receptacles epaleate or rarely paleate, palea 0–1, linear, 6.5–7 × 0.5–0.9 mm, 1-veined, apex and abaxial surface stramineous, ciliate, eglandular. Florets 6–24, corollas 4.2–6 × 0.4–1 mm, lilac, lobes glabrous to puberulous, glandular or rarely eglandular. Cypselas oblong to obconical, 2.3–3.9 × 0.5–0.8 mm, 5–8-ribbed, ribs and sinuses glabrous to setuliferous, eglandular, pappus setae ca. 30–40, white to stramineous, 4.3–5.8 mm long.

Distribution: — Argentina , Brazil, Paraguay and Uruguay. In Brazil, it occurs in Rio Grande do Sul and Santa Catarina. In Rio Grande do Sul, occurs in the physiographic regions of Campanha, Campos de Cima da Serra, Depressão Central, Encosta Inferior do Nordeste, Encosta Superior do Nordeste, Missões, Planalto Médio and Serra do Sudeste ( Fig. 24 , circles).

Habitat: —Grasslands in both Atlantic Forest and Pampa biomes, particularly in the latter, usually close to rocky outcrops or in shallow soils.

Phenology: —Flowers from the end of spring to the end of summer, with a flowering peak between November and February.

Etymology: —Latin squarrulosus (diminutive of squarrosus: squarrose), in reference to the outer involucral bracts with squarrose apices.

Comments: — Chromolaena squarrulosa is a common species in the lower half of Rio Grande do Sul, in grasslands of the Pampa biome, where it is one of the most common species of Chromolaena . The species also occurs in grasslands of the Atlantic Forest, althought in a lesser degree, and, in general, bearing morphologies considered atypical. The most distinguishable feature of this species is the presence of outer involucral bracts with squarrose and tomentose apices, leaving the involucres with a unique appearance.

Eupatorium ascendens var. parcisetosum was described by Robinson (1923), based on a specimen collected by Saint-Hilaire in Rio Grande do Sul. According to the author, this variety differs from E. ascendens ( C. ascendens ) by the sparser indumentum of stems and leaves. On the other hand, the typical variety, E. ascendens , was described some 50 years earlier by Baker (1876) and should occur only in the Brazilian state of Minas Gerais, while E. ascendens var. parcisetosum was recorded only in Rio Grande do Sul. When reestablishing Chromolaena, King & Robinson (1970c) recombined E. ascendens to C. ascendens , but did not consider the variety described by Robinson (1923), which was never synonymized under any other valid name nor recombined to Chromolaena , leaving it as an uncertain name. Despite that, E. ascendens var. parcisetosum (and, by extension, C. ascendens itself) is a common name used by collectors in Rio Grande do Sul to identify specimens of Chromolaena with decumbent habit and sparse indumentum, which were actually specimens of C. congesta or C. latisquamulosa . After examining several specimens in herbaria and in the field, we were able to note that E. ascendens var. parcisetosum differs from E. ascendens by a number of other characters, such as the general appearance of the involucres and some characters (indumentum, size and curvature) of the involucral bracts, the size of capitula, florets and cypselas, the number of florets and pappus bristles.

In fact, E. ascendens var. parcisetosum is more similar to C. squarrulosa . The type specimens of boh species are clearly different, but there is a notable morphological continuum connecting them, and both share the outer involucral bracts with squarrose and tomentose apices, a character usually considered as diagnostic of C. squarrulosa . We observed that specimens more similar to the type of E. ascendens var. parcisetosum tend to show a sparser indumentum in stems and leaves and a lower number of florets, as well as tend to occur in the northern half of the state, in grasslands of the Atlantic Forest biome. Meanwhile, specimens closer to the type of C. squarrulosa tend to show a denser indumentum and a greater number of florets, and are more common in the Pampa biome. However, due to the continuum observed between both morphotypes and the occurrence of the characteristic outer involucral bracts of C. squarrulosa in both of them, we have decided to synonymize E. ascendens var. parcisetosum under C. squarrulosa . Further studies with different approaches should be taken to better clarify the relationship between both morphotypes and their statuses as valid species or not.

As commented under the description of C. congesta , C. squarrulosa is considered part of the “ Chromolaena congesta group”. Cabrera (1996) and Freire & Ariza Espinar (2014b) consider both as synonyms, but we disagree mostly due to the unique features of the involucres of C. squarrulosa .

Specimens examined: — BRAZIL: Rio Grande do Sul: Alegrete: Cerro do Tigre , 11 February 1990, Falkenberg, D. & Sobral, M. 5191 ( ICN). Arroio dos Ratos: s.l., October 1977, Pedersen, T. M. 11971 ( MBM) ; Granja Faxinal , 24 October 1977, Hagelund, K. 11960 ( ICN) ; 20 November 1977, Hagelund, K. 12022 ( ICN) ; 11 April 1982, Hagelund, K. 13908 ( ICN). Caçapava do Sul: Mina Iruí , April 1985, Sobral, M. 3809 ( ICN) ; BR-290, 02 May 1986, Wasum, R. s. n. ( HUCS1606 ) ; Pedra do Segredo , June 1986, Sobral, M. et. al. 5106 ( ICN) ; BR-153, entre km 488 e 489, 01 January 1994, Dombrowski, L. T., Pott, V. et. al. 6435 ( MBM). Caibaté: Caaró, 28 January 1938, Rambo, B. s.n. ( PACA3039 ). Canoas: s.l., January 1939, Luis, I. T. s.n. ( ICN31946 ). Cerro Largo: s.l., 1946, Augusto, I. s.n. ( PACA37165 ). Caxias do Sul: Criúva, 19 December 2012, Gaio, J., Grizzon, M., Scur, L. & Marchett, C. 211 ( HUCS). Cruz Alta: s.l., 02 January 1954, Pivetta, J. 371 ( PACA) ; 29 December 1966, Lindeman, J. & Haas, H. 3895 ( MBM) ; s.l., December 1986, Sobral, M. 5290 ( ICN). Guaíba: BR-116, Km 32, December 1975, Matzenbacher, N. I. 158 ( ICN) ; Fazenda São Maximiano , 11 March 1978, Matzenbacher, N. I. s.n. ( ICN43761 ) ; 16 December 2007, Matzenbacher, N. I. s.n. ( ICN153242 ) ; 21 January 2009, Alves, T. L. S. 30 ( ICN) ; 23 April 2012, Matzenbacher, N. I. s.n. ( ICN173751 ). Jaquirana: propriedade do seu Angelo, 18 March 2012, Christ, A. L. 380 ( ICN). Jari: s.l., 25 January 1942, Rambo, B. s.n. ( PACA9089 ). Manoel Viana: s.l., 05 December 2007, Schneider, A. A. 1568 ( ICN). Porto Alegre: Vila Manresa, 06 October 1931, Rambo, B. s.n. ( PACA1607 ) ; Morro da Vila Manresa , January 1942, Rambo, B. s.n. ( PACA29785 ) ; s.l., 03 February 1950, Sehnem, A.. s.n. ( PACA50656 ) ; Morro do Osso , 18 April 1996, Rodrigues, R. S. 258 ( ICN) ; 04 January 2006, Ferreira, P. M. A. & Eggers, L. s.n. ( ICN149412 ) ; Morro Santana [30°03’10,3’’S, 51°07’44’’W], 13 December 2007, Fernandes, A. C. & Ritter, M. R. s.n. ( ICN158475 ) ; 21 March 2017, Christ, A. L. 395 ( ICN). Quaraí: s.l. [30°27’S, 56°13’W], 30 November 2016, Christ, A. L. 324 ( ICN) ; 30 November 2016, Christ, A. L. 327 ( ICN) ; Cerro do Jarau, 01 December 2016, Christ, A. L. 331 ( ICN). Rosário do Sul: Serra do Caverá [30°10’S, 55°07’W], 29 November 2016, Christ, A. L. 321 ( ICN). Santa Maria: Estação Experimental da Silvicultura , 03 February 1956, Camargo, O. R. 235 ( PACA) ; Morro Pedra do Lagarto, 19 November 2014, Schaefer, J. 228 ( SMDB). Santiago: estrada Santiago-São Borja, 75 km após Santiago, 04 December 1973, Porto, M. L. 632 ( ICN). Santo Ângelo: Granja Piratini, 02 February 1976, Hagelund, K. 10079b ( ICN). São Francisco de Assis : Gruta São Tomé, 20 April 2008, Bruisma, G. 42 ( ICN) ; 21 November 2008, Freitas, E. M. 612 ( HVAT). São Francisco de Paula: Cazuza Ferreira , 11 February 2001, Wasum, R. 934 ( MBM, HUCS) ; Linha São Paulo, 10 February 2002, Wasum, R. 1323 ( HUCS). São Gabriel: Fazenda Santa Cecília , January 1944, Rambo, B. s.n. ( PACA25778 ) ; Distrito de Palma , 03 October 2014, Barão, C. F. 60 ( HBEI). São Leopoldo: Sapucaia, 22 November 1948, Rambo, B. s.n. ( PACA38643 ). Sapucaia do Sul: Morro Sapucaia, 03 January 1956, Rambo, B. s.n. ( PACA59224 ). Taquari: s.l., 10 December 1957, Camargo, O. R. 2855 ( PACA). Tupanciretã: Ijuisinho, 30 January 1942, Rambo, B. s.n. ( PACA10113 ) ; s.l., 26 January 1964, Pivetta 363 ( PACA) ; December 1986, Sobral, M., Deghan, B. & Webster, G. 5329 ( ICN). Viamão: Bairro Tarumã, região de entorno do lago Tarumã [30°04’0,25’’S, 51°01’22,69’’W], 23 October 2008, Silva Filho, P.J.S. 749 ( ICN) .

Figures

FIGURE 24: Distribution of C. squarrosoramosa (triangles) and C. squarrulosa (circles) in Rio Grande do Sul.

FIGURE 25A–E: Chromolaena squarrulosa. A. Fertile specimen. B. Capitulum. C. Involucral bracts. D. Floret. E. Palea. F–I: Chromolaena ulei. F. Fertile branch. G. Capitulum. H. Involucral bracts. I. Floret.

FIGURE 28A–B: Chromolaena squarrosoramosa. A. Primary capitulescence. B. General view. C–D: Chromolaena squarrulosa. C. Secondary capitulescence. D. Leaves. E–F: Chromolaena verbenacea. E. Secondary capitulescence. F. Leaves. Credits:Anderson Christ (A–C, E–F) and Sérgio Bordignon (D).