Chromolaena odorata (Linnaeus) 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 : 176-178

2.10. Chromolaena odorata (Linnaeus) King & Robinson (1970c: 204) .

Eupatorium odoratum Linnaeus (1759: 1205) . Osmia odorata (L.) Schultz-Bipontinus (1866: 252). Lectotype (designated by King & Robinson 1975: 925):— JAMAICA, Plukenet, Phytographia 177, fig. 3.

= Eupatorium floribundum Kunth in Bonpland et al. (1818: 92). Osmia floribunda (Kunth) Schultz-Bipontinus (1866: 252) . Type:— PERU. Catamayo, s.d., A. Humboldt & A. Bonpland 3426 (holotype P! [P00320074]).

= Eupatorium divergens Lessing (1830: 138) . Type:— MEXICO. Hacienda de la Laguna, s.d., Schiede 294 (B, probably lost, Field Museum Berlin Negative 16246!).

= Eupatorium clematitis Candolle (1836: 144) . Osmia clematitis (DC.) Schultz-Bipontinus (1866: 252) . Type:— PERU. s.l., 1834, E.F. Poeppig 3108 (holotype G-DC! [G00465937], isotype F! [V0043564F]).

= Eupatorium graciliflorum Candolle (1836: 145) . Osmia graciliflora (DC.) Schultz-Bipontinus (1866: 252) . Type:— MEXICO. s.l., s.d., T. Haenke s.n. (syntype G-DC! [G00494024]); Acapulco, s.d., W.F. Karvinski s.n. (syntype G-DC! [G00494014]).

= Eupatorium conyzoides var. incanum Baker (1876: 278) . Type:— BRAZIL. Bahia, s.d, Salzmann, Blanchet , F. Sellow 565 (syntypes not found); Mato Grosso, Cuiabá, s.d. A. L. P. S. Manso 91 (syntype BR! [ BR0000005268146 ]) .

= Eupatorium conyzoides var. pauciflorum Baker (1876: 278) . Eupatorium odoratum var. pauciflorum (Baker) Hieronymus (1901: 564) . Type:— BRAZIL. s.l., s.d., Riedel 358 (syntype not found); SURINAME. s.l., s.d., H.R. Wullschlägel 883 (syntype BR! [BR0000013477837]).

= Eupatorium klattii Millspaugh (1900: 105) . Type:— CUBA . Santiago Bay, s.d., C.F. Millspaugh 1126 (F! [V0050130F]).

= Eupatorium conyzoides var. scaberulum Hassler (1916: 279) . Type:— PARAGUAY. Cordillera: Ipacaray, July 1913, E. Hassler 11859 (holotype G, isotype BAF, K! [K001089826]). ( Fig. 17F–J , 18D–E ).

Subshrubs to shrubs, up to 2 m tall, reclining, rarely erect, xylopodium absent, branched along stem and in capitulescence; stems glabrescent to puberulous, glandular or eglandular, leafy until the capitulescence. Leaves 3.2–9.8 × 0.9–4.3 cm, opposite, petiolate, 3-veined, leaf blade ovate to lanceolate, papyraceous to chartaceous, apex acute to attenuate, base rounded to truncate, margins entire in apical half, serrate in basal half, adaxial surface strigose, eglandular, abaxial surface strigose to tomentose, glandular, margins ciliate, petioles 0.4–1.5 cm long, puberulous to tomentose, glandular or eglandular. Primary capitulescences corymbose. Secondary capitulescences candelabra-shaped, sometimes paniculate, axis strigose to puberulous, glandular or eglandular, bracteate, bracts 0.9–9.2 × 0.3–3.8 cm, sometimes with margins entire in both halves, petioles 0.2–1.2 cm long, puberulous to tomentose, eglandular. Capitula sessile to pedunculate, peduncles up to 1.8 cm long, strigose to puberulous, glandular or eglandular, involucres cylindrical, 8.2–9.6 × 2.6–3.5 mm, involucral bracts 23–32, 5–7-seriate, outer ovate to oblong, 1.6–3.1 × 0.9–1.8 mm, apex rounded to rarely obtuse, citrine, ciliate or eciliate, puberulous, glandular or eglandular, appressed, abaxial surface white to citrine, 3–5-veined, glabrous to puberulous, inner linear, 7.4–9 × 0.5–1 mm, apex rounded, citrine to pink, non-petaloid, ciliate or eciliate, glabrous, eglandular, appressed, abaxial surface white to citrine, 1–3-veined, glabrous, receptacles epaleate or rarely paleate, palea 0–1, linear, 8.4–8.7 × 0.5–0.6 mm, 1-veined, apex pink, abaxial surface white, eciliate, eglandular. Florets 17–23, corollas 4.6–5.9 × 0.4–1 mm, lilac or white, lobes glabrous, eglandular. Cypselas obconical, 3.1–4.8 × 0.4–0.7 mm, 4–6-ribbed, ribs and sinuses setuliferous, eglandular, pappus setae ca. 25–38, white to stramineous, 5.1–6.1 mm long.

Distribution: —Tropical America, from southern United States to northern Argentina , and as an invasive species in several countries in Africa, Asia and some Pacific islands ( Esteves 2001). In Brazil, it occurs in all states. In Rio Grande do Sul, it occurs in the physiographic regions of Alto Uruguai and Missões ( Fig. 19 , circles).

Habitat: —Forest edges mostly in the Atlantic Forest biome, rarely in the Pampa.It is also common in anthropogenic sites, such as roadsides.

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

Etymology: —Latin odoratus (aromatic, odoriferous), with reference to the sweet and pleasant aroma present in the florets of the species.

Comments: — Chromolaena odorata is one of the species of Chromolaena with the largest geographic range, along with C. laevigata and C. ivifolia , occurring throughout most of the American continent. It is also the only species of Chromolaena found outside of the New World, even though as an invasive.

There is a historic confusion in Rio Grande do Sul involving C. odorata and C. margaritensis (and their basyonyms E. odoratum and E. margaritense ), which has lead to several misidentifications in the examined specimens. These issues begun with the study of Matzenbacher (1979), in which the author cited E. margaritense for the first time in the state, based on Hagelund 11244, a collection made in Turvo State Park in 1977. This specimen, however, consists of C. odorata , a species common in the region of the park. Since then, several specimens of C. odorata collected in the state have been consistently identified as C. margaritensis , leading to a lot of identification problems between both species, which is aggravated by the fact that C. margaritensis is not native to Rio Grande do Sul. This species occurs in Brazil only in the state of Mato Grosso do Sul. Chromolaena odorata differs from C. margaritensis by the usually reclining habit, the candelabra-shaped capitulescences, the greater number of florets and involucral bracts, the broader leaves with serrate margins in the lower half and the indumentum of the involucral bracts, which is never tomentose as in C. margaritensis .

Among the species found in Rio Grande do Sul, C. odorata is mostly confused with C. pedunculosa . It differs from the latter by the reclining habit, the candelabra-shaped capitulescences, the usually entire margins in the apical half of the leaves and their more ovate shape, the denser indumentum of the adaxial surface, the general aspect of the involucres and by the indumentum of the outer involucral bracts and cypselas.

There are also several identification problems involving this species and C. maximiliani (Schrad. ex DC.) R.M.King & H.Rob. , another species not found in Rio Grande do Sul. Both share the usually reclining habit (although it is more common in C. odorata ) and the candelabra-shaped capitulescences. Due to the great morphologic variations found in C. odorata in other states of Brazil, it seems to be problematic to distinguish between both species using most characters; however, we agree with Esteves (2001), who indicated that C. maximiliani lacks glandular hairs in the abaxial surface of the leaves.

Specimens examined: — BRAZIL: Rio Grande do Sul: Derrubadas: Parque Estadual do Turvo , 17 March 1977, Hagelund, K. 11244 ( ICN) ; July 1981, Brack, P. & Sobral , M. et al. ( ICN50408 ) ; 15 April 1983, Sobral, M., Jarenkow, J. A., Stehmann , J., Bonatto, S. & Paiva, M. 2014 ( SP, MBM) ; 27 March 1988, Mattos, J. 21463 ( HAS). Giruá : entre Giruá e Santa Rosa , 02April 1979, Hagelund, K. 12721 ( ICN) ; 03April 1979, Hagelund, K. s.n. ( ICN45725 ). Marcelino Ramos: Sétimo Céu [27°28’02,8’’S, 51°54’18,8’’W], 06 May 2008, Schneider, A. A. 1605 ( ICN). São Nicolau: Foz do rio Ijuí, 21 May 1989, Brack, P. s.n. ( MPUC6550 ). Três de Maio : BR-462, Km 134, 13 April 2017, Christ, A. L. 434, 438 ( ICN) .

Figures

FIGURE 17A–E: Chromolaena latisquamulosa. A. Fertile specimen. B. Capitulum. C. Involucral bracts. D. Floret. E. Palea. F–J: Chromolaena odorata. F. Fertile branch. G. Capitulum. H. Involucral bracts. I. Floret. J. Palea.

FIGURE 18A–C: Chromolaena latisquamulosa.A. Secondary capitulescence. B. Leaves. C. Xylopodium. D–E: Chromolaena odorata. D. Secondary capitulescence. E. Fertile branch. Credits:Anderson Christ (A–C) and Sérgio Bordignon (D–E).

FIGURE 19: Distribution of C. latisquamulosa (triangles) and C. odorata (circles) in Rio Grande do Sul.