Chromolaena elliptica (Hooker & Arnott) King & Robinson (1970: 200)

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 : 159-160

2.4. Chromolaena elliptica (Hooker & Arnott) King & Robinson (1970: 200) .

Eupatorium ellipticum Hooker & Arnott (1836: 240) . Lectotype (designated by Freire & Ariza Espinar 2014b: 332):— BRAZIL. Rio Grande do Sul, s.d., J. Tweedie s.n. (K! [K000486789], isolectotype GH! [GH00007648]).

= Eupatorium umbelliforme Dusén in Malme (1933: 33). Chromolaena umbelliformis (Dusén) King & Robinson (1970: 207) , syn. nov. Lectotype (designated by Christ & Ritter 2018: 112):— BRAZIL. Paraná: Capão Bonito, 20 March 1915, P. Dusén 16853 (S! [S-R-8982]). ( Fig. 8F–J , 9D–F )

Subshrubs, up to 50 cm tall, decumbent, rarely erect, xylopodium present, branched from base or only in capitulescence; stems puberulous to tomentose, glandular or eglandular, leafy only in lower half, then aphyllous or near-aphyllous in upper half, rarely leafy until capitulescence. Leaves 1.5–11.5 × 0.4–3.8 cm, opposite, sessile to petiolate, 3-veined, leaf blade elliptic, chartaceous to coriaceous, apex acute to rounded, base acute to cuneate, margins crenate to serrate, rarely dentate in apical half, entire in basal half, adaxial surface strigose on veins, eglandular to rarely glandular, abaxial surface strigose to tomentose, rarely strigose only on veins, glandular, margins ciliate; petioles up to 1.4 cm long, puberulous to tomentose, glandular. Primary capitulescence corymbose. Secondary capitulescence corymbose or umbel-like; axis puberulous to tomentose, glandular, bracteate; bracts 0.7–5.6 × 0.2–1.8 cm, sometimes with margins entire, petioles up to 0.9 cm long, puberulous to tomentose, glandular. Capitula sessile to subsessile, peduncles up to 0.5 cm long, strigose to tomentose, glandular, involucres cylindrical to campanulate, 4.9–6.8 × 2.4–4.2 mm, involucral bracts 14–19, 4–6- seriate, outer ovate to ovate-oblong, 1.5–3.4 × 0.7–1.8 mm, apex obtuse to truncate, vinaceous, ciliate, puberulous, glandular, recurved to slightly recurved, abaxial surface stramineous to citrine, 3-veined, puberulous, inner linear, 4.4–6.6 × 0.6–1.2 mm, apex acuminate to obtuse, vinaceous, non-petaloid, ciliate, puberulous, glandular, recurved to slightly recurved, abaxial surface stramineous to vinaceous, 1–3-veined, glabrous to puberulous, receptacles epaleate. Florets 8–17, corollas 3.9–5.2 × 0.5–0.9 mm, lilac, lobes glabrous to puberulous, glandular. Cypselas oblong or rarely obconical, 2–2.9 × 0.4–0.9 mm, 5–8-ribbed, ribs setuliferous, sinuses glabrous to setuliferous, glandular, pappus setae ca. 30–38, white to stramineous, 4.2–5.5 mm long.

Distribution: — Argentina , Brazil and Paraguay ( Freire & Ariza Espinar 2014b). In Brazil, it occurs in Paraná, Rio Grande do Sul, Santa Catarina and São Paulo. In Rio Grande do Sul, it occurs in the physiographic regions of Alto Uruguai, Campos de Cima da Serra, Depressão Central, Encosta Superior do Nordeste and Planalto Médio ( Fig. 10 , circles).

Habitat: —Mostly grasslands in the Atlantic Forest biome, rarely in the Pampa. The species can also be found in forest edges, but less often.

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

Etymology: —Latin ellipticus (elliptic), in reference to the shape of the leaves.

Comments: — Chromolaena elliptica is a rare species in Rio Grande do Sul and has been neglected by nearly every author that studied the group since its original description. Most analyzed specimens were misidentified as C. congesta , C. ascendens or C. umbelliformis , the latter considered a synonym of C. elliptica in this study. This synonymy is mostly due to the morphological similarities between the type specimens of both species, but also has taken into account the historical background of both species.

The type specimen of C. elliptica , as indicated by Hooker & Arnott (1936), was identified in K as C. rhinanthacea due to a probable mistake by Baker (1876). Baker cited this specimen as one of the specimens examined for his treatment of Eupatorium rhinanthaceum ( C. rhinanthacea ), which differs from C. elliptica by the indumentum of stems, leaves and involucral bracts, shape and distribution of leaves along the stem and the indumentum and shape of the cypselas. Since Baker (1876) did not include E. ellipticum as a synonym of E. rhinanthaceum , it is probable that the inclusion of the type specimen of the former in the examined material of the latter was simply a mistake, given than, apart from the characters mentioned above, the two species do resemble each other. Chromolaena umbelliformis was later described in Malme (1933) based on specimens collected by Dusén in Paraná and Santa Catarina. Concurrently, Robinson (1933) “rediscovered” E. ellipticum and took into account the issue regarding the type specimen of this species involving Baker (1876). According to Robinson (1933), this explains why E. ellipticum was neglected by authors after Baker (1876), such as Hieronymus (1897). Authors after Robinson, including Barroso (1950), Rambo (1952), Matzenbacher (1979) and King & Robinson (1987) have considered both species as different entities. However, given their geographical ranges, morphological characters and the historic taxonomic problems involved, we decided to consider both species as a single unit.

Chromolaena elliptica shows great morphological variation in some characters, particularly the size of the leaves and the indumentum of leaves and stems. Despite few specimens analyzed and populations found in the wild, it is possible to see a continuum between the different morphotypes identified. The variations observed are attributed to different environmental conditions and should not intervene in the recognition of these populations as a single species.

Chromolaena elliptica is considered part of the “ Chromolaena congesta group”, as explained under the description of C. congesta . As such, it shares morphological continua with other species of the group, particularly C. congesta and C. rhinanthacea . It differs from C. congesta due to the shape of the leaves and their distribution along the stem, the overall characters and appearance of the involucres, the number of florets and the indumentum and shape of the cypselas. The main morphological differences between C. elliptica and C. rhinanthacea have been already mentioned above.

Specimens examined: — BRAZIL: Rio Grande do Sul: Barros Cassal: entre Barros Cassal e Vila Costa, 19 March 1978, Reis, I. 284 ( ICN). Caxias do Sul: Criúva , 25 March 2000, Kegler , A. 914 ( HUCS, MBM). Guaíba : Fazenda São Maximiano , BR 116 , Km 308, 04 April 2011, Matzenbacher , N. I. s.n. ( ICN167144 ). Giruá : Granja Sodal , March 1964, Hagelund , K. 2032, 2033, 2170 ( ICN). Jaquirana : Parque Estadual do Tainhas [29°05’S, 50°21’W], 19 March 2017, Christ, A. L. 386 ( ICN). Nonoai: próximo ao rio Uruguai , March 1945, Rambo, B. s.n. ( PACA28300 ). Passo Fundo: s.l., April 2009, Savaris, M. 60, 61 ( ICN). Porto Alegre: Vila Manresa, 02 November 1931, Rambo, B. s.n. ( PACA526 ) ; Montserrat, 23 March 1949, Rambo , B. s.n. ( PACA40646 ) ; 1949, Emrich, K. s.n. ( PACA47294 ) ; Parque St. Hilaire, 24 March 1976, Mariath, J. 296 ( ICN) .

Figures

FIGURE 8A–E: Chromolaena congesta. A. Fertile specimen. B. Capitulum. C. Involucral bracts. D. Floret. E. Palea. F–J: Chromolaena elliptica. F.Fertile specimen. G. Capitulum. H. Involucral bracts. I. Floret. J. Xylopodium.

FIGURE 9A–C: Chromolaena congesta. A. General view. B. Primary capitulescence. C. Xylopodium. D–F: Chromolaena elliptica. D. Primary capitulescence. E. Leaves. F. General view. Credits:Anderson Christ (A–F).

FIGURE 10: Distribution of C. congesta (triangles) and C. elliptica (circles) in Rio Grande do Sul.