Oxypetalum urceolatum Farinaccio & Goyder, 2016

Farinaccio, Maria Ana & Goyder, David J., 2016, A synopsis of Oxypetalum (Apocynaceae) in Bolivia, with the description of one new species and a key to species in Bolivia, Phytotaxa 267 (1), pp. 16-28 : 24-26

20. Oxypetalum urceolatum Farinaccio & Goyder sp.nov. ( Figure 3 )

The new species differs from O. dactylostelma in having a conical, rather than a grossly expanded, style-head appendage and a glabrous, not pilose, throat to the corolla tube.

Type:— BOLIVIA. Chuquisaca: Luis Calvo, Luis Calvo, Serrania del Iñao, 12 April 2003 (fl), A.O. Carretero, J. Gutierrez, R. Losano & E. Torres 828 (holotypeSPF!, isotype HSB!, MO n.v.).

Vines with white latex, stems tomentose to lanuginose, internodes 8–11 cm, with 1–4 interpetiolar colleters. Leaves opposite; petiole 1–3 cm long, tomentose to lanuginose, smooth, canaliculate distally, with 4 colleters near the insertion of the blade; blades elliptic or orbicular, occasionally lanceolate, 5–9.5 × 2.5–4.5 cm, discolored, adaxial surface lanuginose, abaxial surface tomentose, especially along the margin, chartaceous, with brochidodromous venation, apex acuminate to cuspidate, base cordate. Inflorescence extra-axillary, alternate, umbelliform, 4–15-flowered, open flowers pendant; peduncle 1.5–2.5 cm long, tomentose to lanuginose; pedicels 0.7–1.2 cm long, tomentose to lanuginose. Calyx divided almost to base, lobes 4–6 × 0.85–1 mm, lanceolate, apex acute, pubescent abaxially, glabrous adaxially, 2–3 colleters, when 3, the central is larger, in clusters, below sinus. Corolla cream, yellow, with reddish on outside, urceolate, tube 7–8 mm long, outside pubescent, inside barbellate on proximal half, glabrous on the distal one, lobes 2.5–3 × 1.1–1.5 mm, triangular, sharply recurved, pubescent abaxially, glabrous adaxially, apex acute. Corona cream, lobes 1.1–1.5 × 0.5–0.6 mm, oblong, apex rounded. Gynostegium cream, 2.5 mm long, stipitate, stipe ca. 1–1.3 mm; style-head 2.2–2,5 mm long, conical, thick, entire. Anthers 2–2.2 × 0.9–1 mm, rectangular, terminal appendage 1–1.1 × 0.6–0.8 mm, lanceolate, apex acute, dorsum longer than the wings. Corpusculum 0.61–0.7 × 0.16–0.19 mm, fistulose, elliptic to oblong, apex obtuse, caudicles 0.16–0.19 mm long, flattened, translucent, with horny teeth 0.1–0.13 mm long, curved inward and included. Pollinia 0.85–0.91 × 0.19–0.21 mm, oblong to clavate. Follicles and seeds unknown.

Distribution, ecology, and phenology: — Endemic to Bolivia. Three of the four known collections come from the Bolivian half of the inter-Andean dry valley system that runs north from Tucumán in northern Argentina to Santa Cruz in central Bolivia, from where the Andes then change course and run in a north-westerly direction exposed to considerably higher rainfall. Many species track this N–S axis, a common distribution pattern discussed by Goyder (2004b) in relation to the closely allied genus Philibertia Kunth (1819 : ed. fol. 152; ed. qu. 195). The eastern margins of this zone harbour a moist montane “Tucumán” forest in which our new species occurs. One collection [Nee 50434 (K, NY, SPF)], refers to dry forest at Samaipata, but John Wood (pers. comm.), who has collected extensively in the area, assures us that the Tucumán forest zone extends to this area. Another collection, [Wood & Mercado 20860 (K, LPB)], however, was made in the much wetter Chapare region on the NW axis of the Andes. This is surprising ecologically, and Wood (pers. comm.) regards this extended distribution as anomalous. Morphologically, this collection shows some atypical features compared to the three more southerly specimens. The style-head appendage is somewhat thicker and more fleshy, almost approaching that of Oxypetalum dactylostelma to which one of us (DJG) had compared it originally. The corona lobes are also broader than in the remaining collections of O. urceolatum , but the pollinarium, the morphology of which is generally conservative at the species level in Oxypetalum , is entirely consistent with those of the other collections. The specimens were found growing at 1300–2300 m elev. Flowering appears to occur from October to April.

Conservation status: —Least Concern according to IUCN (2001). Only known from four collections, but over quite a wide geographic range. While many forested areas of the Bolivian Andes are subject to disturbance, Oxypetalum species are often found in degraded forest margins and apparently tolerate disturbance.

Etymology: — The epithet refers to the long corolla tube and relatively short corolla lobes found in this species.

Additional specimens examined (paratypes): — BOLIVIA. Cochabamba: Chapare, 2 km de Corani Pampa, 17 o 06.54’S, 65 o 55.79’W, 2213 m elev. 28 October 2004 (fl), J.R.I. Wood & M. Mercado 20860 (K, LPB). Santa Cruz: Florida, vicinity of Achira Camping Resort, 7 km (by air) NE of Samaipata. Formerly dry forest in valley, 18 o 09’S, 63 o 49’W, 1330 m, 3 November 1999 (fl), M. Nee 50434 (K, NY, SPF). Chuquisaca: Tomina, Zona del Rosal. Camino entre el Puente Azero y Padilla, 19°29’41”S, 64°10’30”W, 1989 m elev, 26 March 2013 (fl), J.R.I.Wood et al. 27652 (K, LPB, USZ).

Discussion and affinities: — Both authors have been aware of collections of this species for some time, but their identity and affinities were confused, with some collections compared to Philibertia , and others to Oxypetalum dactylostelma or O. fuscum . Phylogenetic studies of Oxypetalum and the subtribe Oxypetalinae by Farinaccio (2008; Farinaccio et al. in prep.), based on chloroplast and nuclear sequences, helped to place this undescribed species in a wellsupported monophyletic assemblage of South American Oxypetalum , that includes O. erianthum , O. brachystemma , O. dactylostelma , O. dombeyanum , O. molle Hooker & Arnott (1834: 289) , O. pearsonii , and O. fuscum . The close relationship of some of these species had already been suggested by Malme (1927) and Goyder & Fontella-Pereira (2005) on morphologial grounds.

Figures

FIGURE 3. Oxypetalum urceolatum. A. Flowering stem. B. Flower with two lobes removed showing corona and gynostegium. C. Pollinarium. (A–C from holotype, Carretero et al. 828, SPF).