Prestonia succo J.F.Morales, sp. nov. (Fig.1)

A Prestonia quinquangularis, cui similis, foliis 1.5–5.3 ×(0.5–) 0.8–1.6 cm (vs. 6.5–12.5(–20.0) × 2.0–5.5(–10.5) cm), corollae tubo 7.5–8.5 mm longis (vs. 14–20 mm) et coronae appendicibus absenstis differt.

Type: — PERU. Cusco: La Convencion, Santa Teresa, Yantile, 16 March 2004, Huamantupa, Ninanzuro & Huamantupa 4079 (holotype INB!, isotypes AMAZ, CUZ, MO!, MOL, USM!).

Suffrutescent liana. Stem inconspicuously puberulent when young, glabrous to glabrate at maturity, with clear sap, intrapetiolar colleters inconspicuous, up to 1 mm long. Leaves: petiole 2.0– 5.5 mm long; leaf blade 1.5– 5.3 × (0.5–) 0.8–1.6 cm, narrowly ovate to narrowly elliptic, the apex shortly acuminate, the base obtuse to rounded, membranaceous, not revolute, glabrous, secondary veins impressed beneath, inconspicuous adaxially, tertary veins not impressed. Inflorescence cymose, axillary, few-flowered, the pedicels and calyx minutely puberulent, the rachis and peduncle inconspicuously puberulent to glabrate; peduncle 2.5–3.6 cm long, pedicels 10–12 mm long, floral bracts 0.7–1.1 × 0.2–0.4 mm, linear, scarious and inconspicuous. Calyx green; sepals 2.9–3.2 × 1.1–1.3 mm, narrowly ovate, acuminate, inconspicuously puberulent, the colleter laciniate at the apex. Corolla salverform, bright yellow, minutely and inconspicuously puberulent outside, tube 7.5–8.5 × 2.3–3.2 mm, free corona lobes reduced to callous ridges, annular corona slightly 5–lobed, inconspicuous, corolla lobes 5–6 × 4–5 mm, obliquely obovate. Stamens inserted near the corolla mouth, anthers 3.1–3.3 mm long, dorsally glabrous, included or the apices barely exserted. Ovary 1.1–1.3 mm long, glabrous, style head ca. 1 mm long. Nectary irregularly 5–lobed, 1.1–1.3 mm long. Follicles not seen.

Habitat: — Mountainous forest and secondary dry forest at 1800–3250 m.

Distribution: — This species occurs in Peru, where it is endemic to the Department of Cusco.

Etymology: — The specific epithet is an anagram of Cusco, where many Apocynaceae have been collected in the last few years.

Observations:— Prestonia succo is probably related to the widespread P. quinquangularis (Jacq.) Sprengel (1825: 637), but differs in having smaller leaf blades [1.5–5.3 × (0.5–) 0.8–1.6 cm, vs. 6.5–12.5(– 20.0) × 2.0–5.5(–10.5) cm] and corollas without free corona lobes within, with the tube 7.5–8.5 mm long (vs. 14.0–20.0 mm).

Paratype:— PERU. Cusco: La Convención, Santa Teresa, Choquequira, San Ignacio, Suclli et al. 2176 (INB, MO).

In his treatment of the American genera of Echitoideae, Woodson (1936) reported 9 species for Peru [P. acutifolia (Benth. ex Müll.Arg.) Schumann (Engler & Prantl 1895: 188), P. mollis Kunth (Humboldt, Bonpland & Kunth 1818: 221), P. phenax Woodson (1936: 314), P. trifida (Poepp.) Woodson in Gleason & Smith (1933: 392), P. vana Woodson (1936: 323), P. lacerata Woodson (1936: 342), P. tomentosa Brown (1810: 70), P. cordifolia Woodson (1936: 352), and P. riedelii (Müll.Arg.) Markgraf (1924: 26)], whereas Zarucchi (1993) reported three additional species [P. macroneura Woodson (1936: 321), P. plumierifolia Markgraf (1930: 1038) and P. robusta Rusby (1920: 91)]. Some of these taxa were reduced to synonymy (e.g., Gentry 2001, Morales 2010), and a new species was described recently (e.g., Morales 2007). In total, 20 species of Prestonia are currently reported for Peru, two of them endemic (P. racemosa Morales [2007: 153], P. succo [described here]). Prestonia macroneura Woodson (endemic to Brazil) was reported based on Wallnöfer 11–41188 (W, WAG, Z). However, this collection is P. rotundifolia K.Schum. ex Woodson (1936: 318). The status of Prestonia lacerata is unknown, since the type in Berlin was destroyed, and no duplicates are known. Finally, P. cordifolia should be treated as a synonym of the polymorphic P. mollis. A key to the species recognized for Peru is given here.