Oxypetalum lividum Farinaccio, 2013

Farinaccio, Maria Ana & Mello-Silva, Renato De, 2013, Oxypetalum lividum, a new species of Asclepiadoideae (Apocynaceae) from Peru, Phytotaxa 77 (1), pp. 1-4 : 2

Oxypetalum lividum Farinaccio , sp.nov. ( Fig. 1 )

Oxypetalum lividum is similar to O. weberbaueri Schlechter , but it differs by its sessile, 1 – 5-florous inflorescences, pedicels 0.7 – 3.5 mm long, and flowers 9 – 11 mm long, which are borne on short pedicels 0.7 – 3.5 mm long; and by the bluish-green coloration of the leaves, which is unique within the genus.

Type:— PERU. San Martín Department: Tocache Nuevo , Mariscal Cáceres , Quebrada de Cachiyacu , 500 – 600 m, 9 May 1975 (fl, fr), J. Schunke Vigo 8454 (holotype SPF!; isotype MO!) .

Vines, older stems pubescent; young stems tomentose; internodes 14 – 24.5 cm long. Leaves opposite; petioles 2.3 – 4.5 cm long, tomentose, smooth; blades ovate, 6.2 – 8.6 x 3.1 – 4.3 cm, discolor, base cordate to auriculate, apex acute to cuspidate, adaxial surface bluish-green, glabrous or sparsely pubescent on midrib, lateral veins and margins, abaxial surface tomentose, chartaceous, venation brochidodromous, 3 to 4 colleters at base of adaxial side. Inflorescence extra-axillary, alternate, sessile, umbelliform, 1 – 5-flowered; pedicels 0.7 – 3.5 mm long, tomentose. Calyx divided almost to the base, lobes triangular to lanceolate, 5.5 – 5.7 x 0.8 – 1.1 mm, apex round to acute, pubescent above, glabrous below, sometimes with 1 colleters below the sinus. Corolla bright yellowish-green, campanulate, tubes 2.8 – 3.4 mm long, pubescent outside, strongly barbellate inside; lobes lanceolate, 7 – 7.5 x 1.8 – 2.3 mm, twisted, glabrous inside, pubescent outside, margins hyaline, apex acute. Corona lobes connate at the base of the tube, ovate to broadly-ovate, 0.6 – 0.63 x 0.73 – 1 mm, inside with an excrescence from the proximal region up to median lobe, apex acute, undulate, crenate, shorter than the anthers. Anthers quadrangular, 0.6 – 0.8 x 1 – 1.1 mm, terminal appendage lanceolate, 1.2 – 1.5 x 0.5 – 0.6 mm, apex acute, dorsum longer than wings. Corpusculum elliptic to narrowly trullate, 0.78 – 0.82 x 0.14 – 0.16 mm, fistulose, apex obtuse, caudicles 0.11 – 0.17 mm long, flattened, broad, translucent, with horny teeth 0.32 – 0.33 mm long, reflexed outward, free, pollinia oblong, 0.4 – 0.46 x 0.13 – 0.16 mm, curved inwards. Gynostegium 1.1 – 1.5 mm long, sessile, stylehead 4 – 4.3 mm long, terete, bifid from middle, branches divergent, flat. Follicles fusiform, 8 – 9.5 cm long, yellow-green. Seeds unknown.

Distribution, habitat, and phenology: — Oxypetalum lividum is known only from the type locality, at Tocache Nuevo, San Martin Department, Peru, in secondary forest along the Quebrada Cachiyacu, near a mountain stream, at 500 – 600 m elevation. The flowering material was collected during the month of June.

Conservation status:— Oxypetalum lividum is locally rare, with its original habitat having been encroached by cocoa plantations. The use of several types of pesticides might have also eliminated its pollinators ( PRODATU 2008). For these reasons, it should be treated as Vulnerable ( VU A1 acde) ( IUCN 2001 ) .

Etymology:—The specific epithet refers to its bluish-green leaves, as noted by the collector, Dr. José Schunke Vigo.

Discussion: — Oxypetalum lividum is similar to O. weberbaueri , also a rare species known only from the type locality [syntypes Weberbauer 666 (B, F!), Weberbauer 2009 (B, MOL)]. Both species occur at Selva Alva, one of the most biodiverse ecoregions in Peru. This area extends across the eastern slopes of the Andes, stretching from the Amazon to Puno and into some areas of the western flank through the valley of the Marañón River to form a variegated geography ( Brack & Mendiola 2004).

Oxypetalum lividum grows in a zone of the Selva Alta that exhibits higher humidity and soil enriched with minerals derived from the Andean Cordillera ( Brack & Mendiola 2004), while O. weberbaueri grows in the south-central region of the Peruvian Andes, at 1900 – 2000 m altitude. It is a drier and colder area that transitions from the Selva Alta to the Puna.

Oxypetalum lividum is similar to O. weberbaueri , but it differs by its sessile, 1 – 5-florous inflorescences, pedicels 0.7 – 3.5 mm long, and flowers 9 – 11 mm long, which are borne on short pedicels 0.7 – 3.5 mm long; whereas O. weberbaueri has pedunculate, 10 – 20-florous inflorescences, pedicels 5 – 7 mm long, and flowers ca. 20 mm long. The bluish-green leaves of O. lividum may also distinguish it from all other species of the genus.

Figures

FIGURE 1. Oxypetalum lividum Farinaccio. A. Branch with flowers and fruit. B. Flower. C. Pollinarium. (A–C from holotype Schunke Vigo 8454, SPF)