Heliotropium oxapampanum Luebert & Weigend, 2012

Luebert, Federico & Weigend, Maximilian, 2012, Three new species of Heliotropium sect. Heliothamnus (Boraginaceae) from Peru, Phytotaxa 49 (1), pp. 35-44 : 41-43

Heliotropium oxapampanum Luebert & Weigend , spec. nov. (Figs. 2C, 2F, 2I, 5.)

Type: ― PERU. Pasco: Prov. Oxapampa, road to "Pajonal" (Antenna of Oxapampa) and on to Villa Rica , 10º37'19''S, 75º17'26''W, 2515 m, 17 September 2001, M . Weigend , N . Diane , M . Gottschling , H. H . Hilger & J . Skrabal 5776 (holotype HUT, isotypes BSB, M, USM) .

Ascending sparsely branched shrub to 0.8 m tall, with the young branches strigose-pubescent. Leaves alternate, solitary, petiolate, internodes 2–5 cm; petiole 0.5–2.0 cm long; lamina elliptical, discolorous, 5–12 × 1.5–4.5 cm on both flowering and vegetative shoots, base attenuate, apex usually acute or slightly acuminate, limb with the veins conspicuous on both sides, the secondary veins acroscopical, pubescent, strigose on the adaxial surface with simple hairs in the intercostal area, abaxially strigose with bulbous hairs on the veins, hairs longer on the primary and secondary veins and shorter on the tertiary veins. Inflorescences terminal, dichotomously branched up to 4 times, up to 10 cm long overall, with the axes strigose and the terminal branches scorpioid. Flowers complete, sessile, 6–10 mm long. Calyx persistent, not accrescent, with the sepals divided to the base; calyx lobes linear-lanceolate, strigose outside, apically strigose inside, 2.5–4.0 mm long, 0.5–0.7 mm wide at the base, base not broadened, apex acute, not protracted. Corolla infundibuliform, purple, 6–10 mm long, 4.5–9.5 mm wide; lobes rounded, 1–3 × 1.5–3.0 mm; tube strigose outside, glabrous inside. Stamens 3–4 mm long; filaments 1.5–2.5 mm long, arising from the corolla tube, with the distal portion free, free portion 0.2–0.4 mm long. Anthers included, coherent, linear, 1.2–1.6 × 0.3– 0.5 mm, margins shortly paillose especially distally; base rounded, cordate, located approximately 0.5 mm above the apex of the stigmatic head, apex incurved, papillose. Ovary glabrous, 0.4–0.5 mm high, 0.5–0.7 mm wide; disc nectary well developed, 0.7–0.8 mm wide. Style shorter than the stigmatic head, 0.3–0.4 mm long. Stigmatic head conical, with a basal receptive ring, 0.6–0.8 mm long, 0.5–0.6 mm wide at the base, finely papillose. Fruits dry, dehiscent, falling into 4 one-seeded nutlets. Nutlets solid (without cavities), surface reticulate, glabrous, dark brown, 1.0–1.5 × 0.4–1.0 mm. Pollen subprolate, ca. 21–25 × 17–19 µm, 3- colporate, 3-pseudocolpate, sexine psilate (Weigend et al. 5776).

Distribution and habitat:— Known only from the province of Oxapampa (Dept. Pasco) from the eastern slope of the Andes in Central Peru ( Fig. 3 ). The collections are from a sandstone area with dense cloud forest cover on heavily leached sandy soils, and with abundant orchids and ferns on the ground. In this habitat, Heliotropium oxapampanum is found along water courses, usually at the base of stones flanking the water course and on sand banks. This is an extremely unusual substrate and habitat for a species of H. sect. Heliothamnus, which is usually found on loamy soils in at least seasonally dry habitats. Consequently, this species is the only one of the group found in this habitat and this region.

Etymology:— Refers to the province where the species has been collected.

Additional specimens examined (paratypes): ― PERU. Pasco: Prov. Oxapampa, Oxapampa, old road from Oxapampa to Villa Rica , foot path to Antenna , [70º37'S, 75º17'W], 2200–2600 m, 5 April 2001, M . Weigend , K . Weigend , T . Henning & C . Schneider 5493 ( M, MSB, HUT). Sector Chacos pajonal, 10º37'25''S, 75º17'43''W, 3 July 2004, 2100 m, R . Rojas , M . Huaman , A . Peña , J . Mateo & C . Rojas 2659 ( BSB, HUT, MO). Parque Nacional Yanachaga Chemillén, quebrada San Alberto, Refugio El Cedro, 10º32'S, 75º21'W, 2450 m, 27 July 2002, A . Monteagudo , C . Mateo & G . Ortiz 3483 ( BSB, MO) .

This species is morphologically closest to Heliotropium corymbosum , one of the most widespread species of the group. However, H. corymbosum is a species of at least seasonally dry habitats. Heliotropium oxapampanum also differs from H. corymbosum by a style shorter than or equal to the stigmatic head (versus style longer than the stigmatic head in H. corymbosum ) and sepals hirsute and acute (versus strigose and long acuminate in H. corymbosum ) (see Luebert et al. 2010). It also resembles H. mandonii Johnston (1928: 43) in the gross aspect of herbarium material, but the latter species has smaller, white flowers and more coriaceous and rugose leaves. None of these species occur in the same region as H. oxapampanum .

Figures

FIGURE 3. Distribution of the newly described species in Peru.