Chromolaena rhinanthacea (Candolle) King & Robinson (1970c: 205)

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 : 183

2.13. Chromolaena rhinanthacea (Candolle) King & Robinson (1970c: 205) .

Eupatorium rhinanthaceum Candolle (1836: 146) . Osmia rhinanthacea (DC.) Schultz-Bipontinus (1866: 253) . Type:— BRAZIL. São Paulo, 1833, C. Gaudichaud 500 (holotype P! [P02411400], isotype G-DC! [G00494038]). ( Fig. 22A–D , 23D–F ).

Subshrubs, up to 40 cm tall, procumbent, xylopodium present, branched only in capitulescence; stems glabrous, eglandular, leafy until capitulescence. Leaves 4.2–7.5 × 0.9–1.8 cm, opposite or leaves of upper half alternate, sessile, 3-veined, leaf blade elliptic to oblanceolate, papyraceous to chartaceous, apex acute to rounded, base acute to attenuate, margins crenate to serrate in apical half, entire in basal half; adaxial surface glabrous, eglandular, abaxial surface glabrous, eglandular, margins eciliate. Primary capitulescences corymbose. Secondary capitulescences corymbose, axis puberulous, eglandular, bracteate, bracts 0.8–1.4 × 0.1–0.2 cm. Capitula sessile to pedunculate, peduncles up to 0.7 cm long, puberulous, eglandular, involucres cylindrical to campanulate, 5–5.5 × 2.3–3 mm, involucral bracts 14–16, 4–5-seriate, outer ovate to elliptic, 2.2–3 × 0.9–1.5 mm, apex rounded to obtuse, vinaceous, eciliate, glabrous to puberulous, eglandular, slightly recurved, abaxial surface stramineous to citrine, 3–5-veined, glabrous to puberulous, inner linear 4.2–5.2 × 0.8–1 mm, apex acute, vinaceous, non-petaloid, eciliate, glabrous to glabrescent, eglandular, slightly recurved to erect, abaxial surface stramineous to citrine, 2–3-veined, glabrous, receptacles epaleate or rarely paleate, palea 0–1, 5.7 × 0.5 mm, linear, 1-veined, apex and abaxial surface stramineous, eciliate, eglandular. Florets 9–11, corollas 3.9–4.7 × 0.5–0.9 mm, lilac, lobes glabrous to puberulous, eglandular. Cypselas obconical, 2.5–2.7 × 0.5–0.6 mm, 5–6-ribbed, ribs setuliferous, sinuses glabrous to setuliferous, eglandular, pappus setae ca. 28–32, stramineous, 4.3–4.9 mm long.

Distribution: — Brazil, in the states of Minas Gerais, Paraná, Rio Grande do Sul and São Paulo. In Rio Grande do Sul, occurs only in the Aparados da Serra National Park, in the municipality of Cambará do Sul, physiographic region of Campos de Cima da Serra ( Fig. 21 , diamond).

Habitat: —Occurs in highland grasslands in the Atlantic Forest biome.

Phenology: —Flowers during summer, with a flowering peak in December.

Etymology: —The specific epithet is a reference to genus Rhinanthus L. ( Orobanchaceae ),which is morphologically similar to the specimens of this species.

Comments: — Chromolaena rhinanthacea is one of the rarest species of Chromolaena found in Rio Grande do Sul, being recorded only twice in a single locality in the municipality of Cambará do Sul. In general, it is also considered one of the rarest species of the genus in Brazil: Esteves (2001) indicates that the species is probably extinct in São Paulo and is very rare in the states of the Southern region. We agree with this author, since C. rhinanthacea was not collected in Paraná in the last 40 years and was never recorded in Santa Catarina. This species is reported here for the first time in Rio Grande do Sul based on specimens correctly identified: Augusto (1946) cited E. rhinanthaceum based on a specimen collected in the municipality of Cruz Alta, which was not located during our study. However, all other specimens of E. rhinanthaceum collected by this author were actually misidentified specimens of C. ivifolia , which suggests that the specimen cited by Augusto (1946) may also have been incorrectly identified.

Among the species found in Rio Grande do Sul, C. rhinanthacea is closer morphologically to C. gentianoides and C. elliptica . The differences between this species and C. gentianoides were commented under the description of the latter. Chromolaena rhinanthacea differs from C. elliptica by the glabrous stems and leaves and the general characters of the involucral bracts. Chromolaena rhinanthacea is considered part of the “ Chromolaena congesta group” due to its morphological connections to these two aforementioned species, despite being, in general, very distinguishable from C. congesta .

Cabrera (1996) indicated the occurrence of E. rhinanthaceum in Paraguay, based on a collection of Hassler from 1898–1899 deposited in G. This specimen could not be examined. The description made by Cabrera (1996) mentions the presence of tenuous pubescence and glandular hairs in the abaxial surface of the leaves, features not mentioned in the original description by Candolle (1836) and absent from the specimens analyzed in this study, hence why we decided not to consider C. rhinanthacea as occurring in Paraguay. However, it is necessary to analyze this specimen to better clarify the distribution of this species.

Specimens examined: — BRAZIL: Rio Grande do Sul: Cambará do Sul: Itaimbezinho , 12 December 1978, Mattos, J., Mattos, N., Assis, E. & Rosa , H. 19994 ( HAS) ; 06 December 2017, Christ, A. L. 480 ( ICN) .

Figures

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

FIGURE 22A–D: Chromolaena rhinanthacea. A. Fertile specimen. B. Capitulum. C. Involucral bracts. D. Floret. E–I: Chromolaena squarrosoramosa. E. Fertile branch. F. Capitulum. G. Involucral bracts. H. Floret. I. Palea.

FIGURE 23A–C: Chromolaena pedunculosa. A. General view. B. Capitula. C. Leaves. D–F: Chromolaena rhinanthacea. D. Leaves. E. Capitula. F. General view. Credits: Anderson Christ (A, D–F) and Sérgio Bordignon (B–C).