Oxypetalum teyucuarense Farinaccio & Keller, 2014

Farinaccio, Maria Ana & Keller, Héctor Alejandro, 2014, Novelties in Oxypetalum (Apocynaceae-Asclepiadoideae) for the Argentine Flora, Phytotaxa 184 (2), pp. 109-114 : 111-113

Oxypetalum teyucuarense Farinaccio & Keller , sp.nov. ( Figures 1 and 2 )

The new species shares some morphological characters with O. jorgensenii ; both are unbranched erect herbs, the leaf blades, pedicels, pollinia and stylar heads have similar dimensions and the two species possess umbelliform inflorescences. However, O. teyucuarense has a set of features that are unique in Oxypetalum in that it is the only unbranched erect species that is up to 1.50 m tall with calyx lobes pubescent adaxially, and corona lobes with an internal fold, open apically to form a cup, and the thick and ruminate stylar head appendages.

Type: — ARGENTINA. Misiones : San Ignacio, Paraje Teyú Cuaré, 27°16’51.6” S, 55°33’45.1” W, 30 October 2013 (fl), H . A . Keller , R . Ramírez & M . M . Franco 11726 (holotype, CTES!; isotype K!, SI!, CGMS!) .

Plant erect, slender, woody only at the base; 1.30—1.50 m; unbranched, virgate, stem cylindrical, striate when dry, lactescent; glabrous near the base, puberulent towards the apex; nodes pubescent; internodes 4—8 cm long. Leaves opposite; petioles 0.5—1.1 cm long, tomentose, smooth, flanked by 2 colleters proximally; blades ovate, 7.5—11 x 0.5—0.9 cm, concolorous, margin entire, base retuse, apex acuminate to acute, tomentose, chartaceous, venation brochidodromous, 2 colleters at base of adaxial side. Inflorescence umbelliform, extra-axillary, pendent, alternate, peduncles 7.2–10.3 mm long, tomentose; 3—5(-6)-flowered, pedicels 3.6—7.2 mm long, tomentose. Calyx divided almost to the base, green, sometimes brownish, lobes ovate, 4.2—5 x 1.2—1.6 mm, acuminate, tomentose above, pubescent below, 4—6 colleters at the sinus, one larger than the others. Corolla purple to reddish-brown and pubescent outside, yellow with purple dots inside and glabrous, barbellate only at the mouth of the tube, campanulate, tube 2.5—3.5 mm long; lobes oblong, 7.8—8.55 x 1.8—2.2 mm, erect, recurved in the distal third, marginally revolute, apex rounded. Corona pink in lower half, cream above; lobes connate at the base of the tube, oblong, 3.7—5.1 x 0.8— 1.2 mm, taller than the anthers, their adaxial side folded, open and cup shaped above. Anthers quadrangular, 0.5— 0.7 x 0.7—1 mm, terminal appendage lanceolate, 1.2—1.6 x 0.6—0.7 mm, apex acute, dorsum shorter than wings, rectangular, wings prominent. Corpusculum narrowly oblong, expanded distally, spathulate, 0.86—0.96 x 0.06—0,08 mm, apex acute, caudicles 0.12—0.21 mm long, flattened, broad, translucent, with horny teeth 0.12—0.14 mm long, reflexed outward, free, pollinia oblong, 0.40—0.48 x 0.13—0.18 mm. Gynostegium yellow-greenish, 1.7—2 mm long, sessile, stylar head 5,6— 6.1 mm long, purple-greenish, exserted, channeled and 5-angled in lower half, purple, thick and ruminate in the upper half, this portion bifid from middle, branches, flat. Follicles green, fusiform, ca. 6.5 cm long, only one developing. Seeds light brown, ovate, ca. 5 x 2.5 mm, rugose, with a toothed margin, coma white, 2.7—3 cm long.

Distribution, habitat, and phenology: — Oxypetalum teyucuarense is endemic to Teyú Cuaré, San Ignacio, Misiones, Argentina. Its slender, flexible stems rise over a sparse cover of tall grasses. The specimens were found growing within the crevices of a rocky sandstone substrate, at ca. 160 m elev., bordered by cerrado (savanna). Flowering occurs from October to January and fruiting in January to February.

Conservation status:— Oxypetalum teyucuarense can be considered very rare, as it is known from only one population of 23 individuals. The area where it was found has ca. 400 m 2 and is situated in a private conservation reserve for ecotourism. This area has been explored by botanists and plant collectors for many years ( Biganzoli & Múlgura de Romero 2004), so it is unlikely that other population of the species occur in the locality. Its conservation status should thus be considered as critically endangered (CR D) ( IUCN, 2001).

The discovery of this new species near Teyú Cuare Provincial Park, but outside the protected area, complements the arguments of Soria (1996) and Fontana (2005) that the protected area of Teyú Cuaré provincial park should be expanded.

Etymology:—The specific epithet refers to the locality Teyú Cuaré, where all of the specimens were collected.

Additional specimens examined (paratypes):— ARGENTINA. Misiones : San Ignacio , Acceso a Parque Provincial Teyú Cuaré, 24 November 2009, H . A . Keller 7740 ( CTES); ibidem, 27°16’51.6”S, 55°33’45.1”W, 11 December 2013 (fl, fr), H . A . Keller & M . M . Franco 11949 ( CTES) .

Discussion: —The erect habit of Oxypetalum teyucuarense , suggests that it belongs to of the clade that includes only erect species of Oxypetalum ( Farinaccio 2008) . It shares some features with O. jorgensenii Meyer (1943: 60–63) , which also occurs in Missiones: both are erect, unbranched herbs with similar-sized leaf blades, pedicels, pollinia and stylar heads as well as umbeliform inflorescences. Despite this overall similarity, O. teyucuarense has a set of features that is unique in the genus. It is the only unbranched erect species that grows up to 1.50 m tall. In addition, its flower morphology is unusual in that the corona lobes present an internal fold that opens at the apex as a cup. The thick apex of the gynoecium is ruminate. The latter feature makes this species easy to recognize in the field. When the tall, slender plants are in flower, they become deflexed.

New Records

1. Oxypetalum oblanceolatum Farinaccio & Mello-Silva (2006: 236) — O. oblanceolatum was described from one collection from the Brazilian State of Paraná ( Farinaccio & Mello-Silva 2006).This species was considered as vulnerable according to IUCN (2001) Red List criteria, but the recent study of the one collection of CORD herbarium ( Thiers 2008) extends its range into Misiones Province, Argentina. Here it grows in a clearing surrounded by a monoculture of Pinus , and thus O. oblanceolatum should still be considered as vulnerable ( IUCN 2001).

Additional collection: — ARGENTINA. Misiones : San Pedro , Arroyo Liso, unos 5 km pasando San Pedro, desvio por ruta 16 hacia el este, 26 o 37’35.1”S, 54 o 01’54.2”W, 590 m, 9 December 2002 (fl), G . Barboza , F . Chiarini , M . Matesevach & C . l Carrizo García 468 ( COR!) .

2. Oxypetalum wightianum Hooker & Arnott (1834: 288) — O. wightianum is broadly distributed in south and southeastern region of Brazil, reaching western Paraguay ( Farinaccio 2005). One new collection of this species into Argentina was identified in Department Iguazú, at the border with Brazil, thus extending its range to Misiones Province.

Additional collection: — ARGENTINA. Misiones: Iguazú. Paraje Aguaray, Lote APSA , rodal 5–6, 27 December 2001 (fl, fr), H . A . Keller & D. Colcombet 1528 ( CTES!) .

Figures

FIGURE 1. Oxypetalum teyucuarense Farinaccio & Keller—A. Branch with flowers. B. Leaf. C. Flower. D. Corona lobes: D1. Adaxial surface, D2.Abaxial surface, D3. Lateral view, D4. Top view. E. Gynostegium. F. Pollinarium. G. Inmature fruit. H. Opened fruit and seed (A–F from paratype Keller 7740, CTES; G from paratype Keller & Franco 11949, CTES; H examined in field).

FIGURE 2. Oxypetalum teyucuarense Farinaccio & Keller—A. Habitat and habit. B. Flower. C. Flowering branch. (Keller 7740; photos by H. Keller)