Thyrsanthus sulcatus (Nees) C. Ezcurra & A.L.A.Côrtes 2019

Ezcurra, Cecilia, Côrtes, Ana Luiza A. & Daniel, Thomas F., 2019, A synopsis of Thyrsacanthus (Acanthaceae) in Argentina and Paraguay, with notes on generic delimitation, a new combination, and lectotypifications, Phytotaxa 395 (2), pp. 81-88 : 85-86

2. Thyrsanthus sulcatus (Nees) C. Ezcurra & A.L.A.Côrtes , comb. nov. ( Fig. 1A, 1B .)

Basionym: Jacobinia sulcata Nees (1847b: 333) . Siphonoglossa sulcata (Nees) Lindau (1894: 19) . Carlowrightia sulcata (Nees) C. Ezcurra (1993a: 319) . Type:— ARGENTINA. “Rio Parana”, Tweedie s.n. (holotype, K 000529400!).

Dianthera sulcata Griseb. (1874: 224) . Type:— ARGENTINA. Córdoba, Im Camp suedl. von Cordoba, Sommer 1871, Lorentz 116 (lectotype designated here GOET 000057!; isolectotypes B destr. Fot. F 8798!,K000529401!); In campis ab urbe meridionalibus, “1872”, Lorentz s.n. (possibly isolectotype, SI 000706!) .

Siphonoglossa gentianifolia Lindau (1905: 370) . Type:— PARAGUAY. Gran Chaco, Santa Elisa, lat.S 23 o 20’, ad marginem silvarum, Rojas 2841 in herb. Hassler (holotype B destr. photo F 8795!, lectotype designated here G 00102014!).

Perennial herb 10–30 (–50) cm tall, branches subcylindric, octocostate, sulcate between the ribs, puberulous or glabrous. Leaves sessile; lamina 3–5 cm long, 0.4–1(–2) cm wide, lanceolate to narrowly ovate, cuneate to rounded at the base and acute at the apex, coriaceous, generally glabrous. Inflorescence of sessile flowers in dense terminal spikes 1–7 (–12) cm long. Bracts lanceolate, similar to the leaves but smaller and narrower; bracteoles lanceolate, somewhat longer than the calyx, glandular-puberulous. Calyx 0.6–1 cm long. Corolla white to pale blue or lilac, 1.5–2 cm long, with a long narrow tube 1–1.3 cm long and less than 2 mm diam.at the orifice, throat very short and slightly widening in the orifice, upper lobe erect, emarginate, 5 mm long, 2 mm wide, and the three divergent lower lobes 5 mm long, 3 mm wide, patent. Stamens 2, very shortly exserted; filaments 2–2.5 mm long; anthers 1.5 mm long. Ovary puberulous; style thin and prolonged beyond the anthers. Capsule 1.5–2 cm long, puberulous. Seeds 4 or less, ca. 4 mm diam, minutely tuberculate-rugose. Retincula ca. 2 mm long.

Geographic distribution and habitat: — Paraguay and northern and central Argentina. It has also been reported and photographed from northern Uruguay by Andrés Gonzalez (pers. comm., Fig. 1A ), but without herbarium voucher. A heliophilous species, it lives in pastures and fields subjected to periodic fires,from 0 to 1500 m, especially in the Chaco region. It flowers in spring, mainly from October to December.

Notes: — Thyrsacanthus sulcatus is a small herb of open habitats, characterized by its furrowed stems, coriaceous leaves, and pale flowers in terminal spikes. Its flowers are very similar to those of North American Yeatesia Small (1896: 410) , especially of Yeatesia platystegia ( Torrey1859: 126) Hilsenbeck(1989: 435) , as can be seen in Kiel et al. (2014). This similarity is probably the result of parallel evolution in relation to selection for pollination by butterflies (psychophilly), as species of Yeatesia fall in a different clade from Thyrsacanthus ( Kiel et al. 2014, Côrtes et al. 2015). Thyrsacanthus sulcatus can be distinguished morphologically from species of Yeatesia by its placentae that do not separate from the capsule at maturity ( Ezcurra 1994). It is interesting to note that a species described as Yeatesia does belong to the Thyrsacanthus clade (e.g. Y. mabryi Hilsenbeck,1989:436 ; see Kiel et al. 2014, Côrtes et al. 2015), thus rejecting monophyly of Yeatesia .

Regarding types of Grisebach’s names, the protologue of Dianthera sulcata only mentions the locality “ Córdoba, in campis at urbe meridionalibus”.Therefore a specimen collected south from the city of Córdoba, Lorentz 116, GOET 000057, is selected as the lectotype of the name Dianthera sulcata , because it is an abundant specimen that coincides well with the protologue in all aspects, and has the species’ name in Grisebach’s handwriting on the label. A duplicate of this specimen was destroyed at B, and another is at K. An additional specimen from the southern part of the city of Córdoba (“ Córdoba in campis ab urbe meridionalibus”) that was collected by Lorentz but without collection number and with a different year of collection is at SI.We consider it is possibly a duplicate in which the locality has been directly transcribed from the protologue in Latin, and the year miscopied.

As the holotype of Siphonoglossa gentianifolia Lindau at B was destroyed, we here select the isotype G 00102014 as lectotype. This latter specimen matches the destroyed holotype from B of which a photo is extant (F photo negative 8795), and meets the characteristics described in the protologue.

Representative specimens examined: — ARGENTINA. Chaco: Dpto. General Güemes, Camino de Fuerte Esperanza a Taco Pozo, Schinini et al. 24919 (CTES). Córdoba: Dpto. Totoral, Ruta Nacional 9, ca. 1 km. al S de Las Peñas, Pozner 297 (SI, CTES). Corrientes: Dpto. Ituzaingó, Rápidos de Apipé, Schinini 14772 (CTES). Entre Ríos: Dpto. La Paz, ruta 12, Arroyo Barranca Colorada, Bacigalupo 615 (SI). Formosa: Dpto. Patiño: Ruta 95, 1 km al N de Porteño Nuevo, Palacios 355 (SI). Jujuy: Dpto. Capital, camino a El Cadillal, Cabrera 29949 (SI). Salta: Dpto. Capital, La Lagunilla, 5–6 km al E del cerro San Bernardo, 1000 m, Novara 8157 (MCNS). Santiago del Estero: Dpto. Rivadavia, Ruta Nacional 34 entre Selva y Palo Negro, Hunziker 17790 (CORD). Santa Fe: Sin Dpto., Chaco Santafecino, Lynch s.n., BA 3767 (SI). Tucumán: Dpto. Leales, Chañar Pozo, Venturi 537 (SI). Also reported from Catamarca and San Luis ( De Marco & Ruiz, 1976). PARAGUAY. Alto Paraná: Reserva Tatí Yupí, sabana, campo bajo, Itaipú Binacional, s. col. 608 (MO). Chaco: Agua Dulce, 20º14’S, 60º07W, Schinini & Bordas 18098 (MO, SI). Presidente Hayes: Gran Chaco, Santa Elisa, 23º10’S, ad marg. silv., IV.1903, Rojas 2841 (G).

Figures

FIGURE 1. A. Thyrsacanthus sulcatus, flowering plant.B.Thyrsacanthus sulcatus, inflorescence.C.Thyrsacanthus boliviensis, flowering branch. (photographs:A and B from Uruguay by Andrés Gonzalez, C from Bolivia by Thomas Daniel).