Plectocephalus formosus (Ravenna) Penneck. & Gl. Rojas, 2020

Penneckamp, Diego, Chaura, Rodrigo, Rojas, Gloria & Stuessy, Tod, 2020, Taxonomic notes on Plectocephalus (Centaurea s. l., Centaureinae, Asteraceae) from Chile, including new combinations and synonyms, Phytotaxa 437 (4), pp. 227-236 : 230-232

Plectocephalus formosus (Ravenna) Penneck. & Gl. Rojas , comb. nov. ( Figure 3 ).

Basionym:— Centaurea formosa Ravenna (2006: 48–49) . Type:— CHILE: Coquimbo Region, Elqui Province , bushy field near El Arrayán about 25 km north from La Serena , October 2003, P. Ravenna 5023 (Holotype BA; isotypes Herb. Rav., CONC). Neotype:— CHILE. Coquimbo Region: Elqui Province , Panamericana Norte , between La Serena and Caleta Hornos, before Juan Soldado bridge, (29°39’ S, 71°18’ W), 80–190 m, 3 October 1991, Ch. von Bohlen 1209 (holotype SGO 133272 !).

Note:—Although our efforts to locate the type material in the mentioned institutions have been unfruitful, we accept this as a distinct species based on the detailed description. However the type material do not exist at the herbaria cited (BA, CONC, pers. comm.) and the P. Ravenna´s personal herbarium was destroyed (Ravenna’s daughter, pers. comm.), so here we designate a new type specimen for this species name.

Shrub ca. 1.5–2 m tall, branched, lignified at base, perennial. Stems glabrous to glabrescent, striated toward apex. Leaves pinnately-parted to pinnatisect, (2–)2.5–9 × 0.7–2.6 cm, lamina glabrous to glabrescent at adaxial surface and puberulent at abaxial surface with revolute margin. Capitulum borne singly on a glabrescent, striate peduncle, accompanied by some reduced leaves in form of pinnatifid bracts. Involucre globose, hemispheric-campanulate, large, (2–)2.5–3.5(–4) cm diam., woolly-pilose at base. Phyllaries many in 5–7 series. Internal phyllaries of first series sparsely woolly-pilose on adaxial surface at the base and center, becoming glabrous toward margins or rarely glabrescent. External series phyllaries shorter and wider, subcordate, ovate to ovate-lanceolate with acute apex, 5–10 × 5–7 mm, inner phyllaries longer and narrowly lanceolate, linear-lanceolate to subspathulate, 25 × 2–5 mm, with apex expanded into an erect spreading pectinate-fringed coriaceous appendage, brownish, being c. 1/3 to equaling inner phyllary length or even external phyllary length. Phyllaries with fimbriate appendage with a long mucro at apex. Ray florets sterile, 3.5–5 × 0.4–0.5 cm, corolla 5-lobed, lobes lanceolate with apex acute, 2.5 × 0.3–0.4 cm, tube 1.5–2.5 cm long. Disc florets tubular, smaller than ray florets, fertile and hermaphroditic, 2–2.3 × 0.2–0.3 cm, corolla 5-lobed, lobes acute to linear-lanceolate separated at least 1/5 to 1/4 of length. Corollas very showy, ligules pink to whitish, disc floret corollas whitish-yellow. Style 8–10 mm with bilobed stigma, stigma branches ca. 3 mm. Anthers ca. 7 mm long. Pappus and mature cypselae not seen.

Etymology:—From the Latin, formosus , meaning beautiful, because this species has large and very showy ornamental flowers, having one of the largest capitula in the genus.

Distribution and ecology:—Restricted to sclerophyllous shrublands in coastal areas of Juan Soldado north of La Serena, Coquimbo Region (ca. 29°39’31.00” S, 71°18’42.00” W) and in the range of Chañaral de Aceituno (ca. 29°3’60.00” S, 71°29’0.00” W) in the Atacama Region.

Notes:—This species was proposed by Ravenna (2006) in a little-known journal, but nonetheless effectively published.The name was also validly published because the author provided a description, type specimen, and indicated the institution of deposit. Since the species appears to be a good one, and for clarity with regard to the other species of Plectocephalus in Chile, we provide a new comprehensive description and key.

Plectocephalus formosus resembles P.floccosus , which differs by lacking woolly-tomentose stems. Plectocephalus formosus is also similar to P. chilensis , from which the former differs in the abaxial puberulent surface of the leaves.

One might speculate that based on intermediate morphological features and distribution, P. formosus might have originated through hybridization between P. chilensis and P. floccosus . This might be an example of a recent speciation radiation that occurred in this region of the distribution of Plectocephalus (A. Susanna, pers. comm.).

Specimens examined: — CHILE. Atacama Region: Huasco Province: Chañar de Aceitunas , 60 km al W. de Domeyko (29°7’ S, 71°25’ W), 300–500 m, 8 Sep 1949, W. Biese 2544 ( SGO 104196 ) . Coquimbo Region: Elqui Province: Juan Soldado (29°48’ S, 71°15’ W), 100 m, 12 Oct 1965, C. Muñoz 48 ( SGO 135306 ) ; Quebrada de Juan Soldado , al N de La Serena, por la carretera panamericana (29°48’ S, 71°15’ W), 110 m, 17 Sep 1957, C. Muñoz 4296 ( SGO 118488 ) ; La Serena, 30 km N (29°37’ S, 71°17’ W), 30 m, 25 Dec 1971, K. Beckett , M. Cheese & J. Watson 4678 ( SGO 110041 ) ; Km 490, hacia los roquerios (29°45’ S, 71°19’ W), 200 m, 21 Oct 1984, M. Muñoz 1914 ( SGO 108070 ) ; El Tofo (29°27’ S, 71°15’ W), 300 m, 15 Oct 2006, N. Schulz 9 ET ( SGO 154742 ) .

Figures

FIGURE 3. Plectocephalus formosus: A, type specimen; B, living plant in natural habitat, photograph by Gloria Rojas.