Heliotropium maranjonense Luebert & Weigend, 2012

Luebert, Federico & Weigend, Maximilian, 2012, Three new species of Heliotropium sect. Heliothamnus (Boraginaceae) from Peru, Phytotaxa 49 (1), pp. 35-44 : 36-38

Heliotropium maranjonense Luebert & Weigend , spec. nov. ( Figs. 1 , 2D, 2G.)

Type:― PERU. Amazonas: Prov. Chachapoyas, road from Chachapoyas to Mendoza , 06º13'08''S, 77º50'03''W, 2030 m, 20 October 2000, M . Weigend , E . Rodríguez , H . Förther & N . Dostert 2000/871 (holotype USM, isotypes BSB, HUT, MSB) .

Erect shrub, densely branched, to 1.8 m tall with the young branches densely lanose-pubescent. Leaves alternate, solitary or crowded at the apex of the branches, shortly petiolate, internodes 0.5 – 1.5 cm; petiole 0.5–1.0 cm long; lamina lanceolate, discolorous, 3.0–9.0 × 1.3–3.0 cm on both flowering and vegetative shoots, base cuneate, apex acute, limb with the veins well-marked on both sides, the secondary veins acroscopical, strigose-pubescent, finely rugose on the adaxial surface, densely lanose on the abaxial surface, pubescence homogeneously distributed. Inflorescences apical, dichotomically branched up to 4 times, to 5 cm long overall, with the axes densely lanate and the terminal branches scorpioid. Flowers complete, sessile to shortly pedunculate, 4–6 mm long. Calyx persistent, not accrescent, with the sepals divided to the base; sepals lineal-lanceolate, lanose outside, glabrous or laxly pubescent inside, 2.5–4.0 mm long, 0.5–1.0 mm wide at the base, base not broadened, apex acute, protracted. Corolla infundibuliform, white, with greenish-yellow centre, 3–5 mm long, 2–4 mm wide; lobes rounded, 0.5–1.5 × 1–2 mm; tube villous outside, glabrous inside. Stamens 2.5–3.0 mm long; filaments 1.5–2.0 mm long, arising from the corolla tube, with the distal portion free, free portion ca. 0.2 mm long. Anthers included, coherent, sagittate, 0.7–1.3 × 0.2–0.3 mm, with the apical margins shortly papillose; base rounded, cordate, located just above the receptive part of the stigmatic head; apex incurved, papillose. Ovary glabrous, 0.3–0.4 mm high, 0.5 mm wide; nectar disk developed, 0.8– 1.0 mm wide. Style longer than the stigmatic head at maturity, 0.8–1.5 mm long. Stigmatic head conical, with a basal receptive ring, 0.7–1.2 mm long, 0.6–0.7 mm wide at the base, papillose. Fruits dry, dehiscent, falling into 4 one-seeded nutlets. Nutlets solid (without cavities), surface slightly reticulate to smooth, glabrous, dark brown, 0.9–1.2 × 0.5–0.7 mm. Pollen subprolate, ca. 17–20 × 13–15 µm, 3-colporate, 3-pseudocolpate, sexine psilate (Weigend et al. 2000/871).

Distribution and habitat:— Known from the interandean valleys of the Marañón and Utcubamba rivers in the provinces of Bolívar (Dept. La Libertad), Celendín (Dept. Cajamarca) and Chachapoyas (Dept. Amazonas) in northern Peru. Rare and localized in scrub forests on dry slopes ( Fig. 3 ).

Etymology:— The name refers to the Marañón valley, from where this species is described.

Additional specimens examined (paratypes): ― PERU. Cajamarca: Prov. Celendín, Canyon of the Rio Marañón above Balsas, 16 km below summit on road to Celendín, km 137 east of Cajamarca, [6°52´S, 78°3´W], 2400 m, 27 May 1964, P. C . Hutchison & J. K . Wright 5400 ( K, MO) . La Libertad: Prov. Bolivar, Balsas to Bolivar , before Longotea , 07º02'15''S, 77º52'56''W, 2303 m, 17 October 2000, M . Weigend , E . Rodríguez-R., H. Förther & N . Dostert 2000/809 ( BSB, HUT, MSB) .

This species is morphologically close to Heliotropium erianthum Johnston (1928: 41) , and H. incanum Ruiz & Pavón (1799: 2) , as well as to H. argenteum Lehmann (1818: 139) . It differs from the latter by an adaxially less dense pubescence and a more rugose and scabrous leaf surface, elliptic-lanceolate leaves (vs. ovate in H. argenteum ) and a style longer than the stigmatic head. From Heliotropium incanum and H. erianthum , it differs in having a more finely rugose and scabrous abaxial leaf surface and sepals more densely lanose. The specimen Hutchison & Wright 5400 was determined by J.J. Wurdack ( US) as Heliotropium cf. argenteum in 1966, with an additional note: "this is not H. erianthum ". This specimen differs from the type and from the other specimen of this species in having slightly broader leaves and in the height of the plant, which is not taller than 0.5 m. The flowers of these specimens were reported to be weakly scented.

FIGURE 2. New species in their natural habitats (A–C) and SEM pictures of adaxial leaf surface (D–F) and inner flower (G–I) of Heliotropium maranjonense (D, G), Heliotropium pamparomasense (A-B, E, H) and Heliotropium oxapampanum (C, F, I). Note the differences in pubescence and texture of leaf surface and the relationship of length between style and stigmatic head. All scale bars equal 1 mm.

Figures

FIGURE 1. Heliotropium maranjonense. A, Flowering branch; B, Leaf, adaxial surface; C, Leaf, abaxial surface; D, Flower, outer view; E, Flower, view of the corolla tube; F, Flower, inner view; G, Sepal abaxial surface; H, Sepal adaxial surface; I, Anther (open). (All from Weigend et al. 2000/871, BSB). Drawn by Stefanie Werner.

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