Polylepis rocio-rojasii L.Valenz. & Villalba

Gamarra, Luis Valenzuela & Valdivia, Maria Isabel Villalba, 2024, A new species of Polylepis (Rosaceae) from the Bosque de Proteccion Pui-Pui, Peru, Phytotaxa 655 (1), pp. 97-104 : 98-103

Polylepis rocio-rojasii L.Valenz. & Villalba sp. nov. Type:— PERU. Junin Region, Prov. Chanchamayo, Dist. Vitoc, Bosque de Proteccion Pui-Pui , Humid Puna Forest , 11°17’04.8”S, 75°11’20.6”W, 3800 m, 17 October 2014. L. Valenzuela et al. 28745 (holotype HOXA!; isotypes MO!, USM!) . Figures 1–4 .

Diagnosis:— Polylepis rocio-rojasii differs from Polylepis canoi in having compound leaves with one pair of lateral leaflets (vs. compound leaves with 2–3(4) pairs of lateral leaflets); rachises 0.7–1.2 cm long, densely lanuginose (vs. rachises 2.5–2.9 cm long, densely sericeous); the stipular sheath apically acute, with three caducous spurs, sericeous in both surfaces (vs. stipular sheaths apically acute, with two persistent spurs, glabrous in both surfaces); shorter inflorescences 6.0–7.0 cm long (vs. 8.2–14.5 cm long); styles 1.7–1.8 mm long (vs. 2.4–3.8 mm long); fruits rounded to ovoid, densely lanuginose (vs. rhomboid, densely sericeous).

Trees up to 9 m tall. Leaves irregularly grouped towards the ends of the twigs, with one pair of lateral leaflets; rachises 0.7–1.2 cm long, channeled, densely lanuginose; points of leaflet attachment with a tuft of rigid silky hairs; stipular sheath 2.2–2.3 × 0.4–0.5 cm, cylindric tubular, covered by sericeous hairs 3–4 mm long in both surfaces, more abundant in the sheaths of young twigs, with three often caducous spurs; central leaflets 3.5–4.5 × 0.8–1.3 cm, obovate-elliptic to oblong-elliptic, base symmetrical, slightly obtuse, margin entire, apex emarginate, petiolule 3 × 1 mm, channeled, lanuginose; adaxial surface sparsely lanuginose, secondary veins immersed, very conspicuous, abaxial surface densely lanuginose, hairs 1.0– 1.2 mm long; lateral leaflets 3.0–4.5 × 0.8–1.0 cm, oblong-elliptic, base asymmetrical, margin entire, apex emarginate, sessile; adaxial surface sparsely lanuginose, secondary veins immersed, very conspicuous, abaxial surface densely lanuginose, hairs 1.0– 1.2 mm long. Inflorescences 6.0–7.0 × 0.12–0.15 cm, pendant, lanuginose, bearing 6–12 flowers; pedicel 2.5–3.0 mm long, cylindric, lanuginose, covered by wavy unicellular hairs 1.0– 1.2 mm long, translucent yellow; floral bracts 7.0–9.0 × 2.2–2.7 mm, ovate-elliptic, acuminate, concave, adaxial surface densely sericeous. Flowers 8–10 mm diam.; sepals 3–4, 4.0–5.0 × 3.6–4.8 mm, triangularovoid, erect, concave, glabrous adaxially, densely sericeous abaxially; stamens 3–9 pairs, arranged in two series (1 st series internal, 1.8–2.0 mm, 2 nd series external, 3.0– 3.5 mm), anthers orbicular, lanuginose, dorsifixed (1 st series 1.3– 1.5 mm long; 2 nd series 1.5–1.8 mm long); styles 1.7–1.8 mm long; ovary 1.2–1.4 × 0.9–1.0 mm, lanuginose; stigma ca. 1 mm diam., irregularly fimbriate with small lamellae. Fruits 3.0–3.5 × 2.8–3.2 mm, rounded to ovoid, densely lanuginose, indehiscent, with 1–7 short cylindrical spines, the apex blunt.

Distribution and ecology:— Polylepis rocio-rojasii is known only from the Bosque de Proteccion Pui-Pui, in the Tingo sector of Vitoc district, where it forms small forest relicts above 3800–4000 m in elevation. The species grows mostly in open areas at the humid Puna hills, where the winds and fog are constant ( Figure 2A ), and it is commonly found together with tree species of Baccharis Linnaeus (1753: 860) , Buddleja Linnaeus (1753: 112) , Citharexylum Linnaeus (1753: 625) , Clethra Linnaeus (1753: 396) , Escallonia Mutis ex L.f. (1781: 156), Gynoxys Cassini (1827: 455) , Hesperomeles Lindley (1837: 23) , Miconia Ruiz & Pav. (1794: 60) , Myrsine Linnaeus (1753: 196) , Prunus Linnaeus (1753: 473) , Solanum Linnaeus (1753:184) , Styrax Linnaeus (1753: 444) , Symplocos Jacquin (1760: 24) and Vallea Linnaeus (1781: 266) , as well as the shrubby Chusquea tessellata Munro (1868: 60) ( Figure 2A ), Diplostephium haenkei Weddell (1857: 203) , and Loricaria lucida Cuatrecasas (1954: 163) ; these taxa could be used for restoring local relict Polylepis forests ( JBM 2014, Ridbäck 2008).

Polylepis rocio-rojasii is currently threatened mainly by anthropogenic activities such as forest burning, cattle farming and grazing expansion, which cause an irreversible reduction and possible disappearance of the small forest relicts where it is found. Moreover, its population has less than 100 mature individuals in an area of ca. 2 km 2. Therefore, following the criteria of the IUCN Red List ( IUCN 2024), the species is considered as critically endangered (CR B2ac(ii, iv), according to its area of occupancy and presence in a single location.

Etymology:—The new species is dedicated to Rocío del Pilar Rojas Gonzales in recognition to her scientific work carried out in Peruvian Andean-Amazonian forests, for her dedication on training professional botanists and ecologists, and for the great management carried out in the Missouri Botanical Garden and the Herbarium Selva Central Oxapampa (HOXA) in Peru.

Taxonomic notes:—The new species belongs to Polylepis sect. Sericeae Boza & Kessler (2022: 54) , which includes trees or shrubs with the abaxial leaflet surfaces with sericeous, lanate or villous hairs, and densely sericeous or villous fruits with a variable number and position of flattened, thin or short spines ( Boza & Kessler 2022).

Polylepis rocio-rojasii is similar to P. canoi due to the shape and size of the leaflets, but it differs by the leaves with one pair of lateral leaflets (vs. leaves with 2–3(4) pairs of lateral leaflets); the points of leaflet insertion with a tuft of rigid, silky hairs, without glandular hairs (vs. points of leaflet insertion with a tuft of long, straight, yellowish hairs, with glandular hairs); the central leaflets obovate-elliptic to oblong-elliptic, apically emarginate, with an entire margin, and densely lanuginose abaxially (vs. central leaflets obovate, apically slightly emarginate, with an entire to slightly serrate margin, and densely sericeous abaxially); the inflorescences 6–7 cm long, lanuginose (vs. inflorescences 8.2– 14.5 cm long, sericeous); the flowers with 6–18 (vs. 13–15) stamens; and the rounded to ovoid fruits, with short cylindrical spines with a blunt apex (vs. rhomboid fruits, with short flat spines).

Figures

FIGURE 1. Polylepis rocio-rojasii L.Valenz. & Villalba. Geographical distribution in Bosque de Protecion Pui-Pui, Peru.

FIGURE 2. Polylepis rocio-rojasiiA: Some individuals of the new species with Chusquea tessellata; B: Branch; C: Trunk with exfoliating rhytidomes D: Trifoliolate leaf and detail channeled petiole, with a tuft of hairs (adaxial); E: Trifoliolate leaf, central leaflet with short petiolule (abaxial). Images by L. Valenzuela.

FIGURE 3. Polylepis rocio-rojasii. A: Branch; B: Stipular sheath (left to right, frontal and lateral view); C: Extended stipular sheath (left, abaxial; right, adaxial); D: Trifoliolate leaf and channeled rachis with a tuft of hairs (adaxial); E: Trifoliolate leaf (abaxial); F: Pendant inflorescence; G: Inflorescence, floral bracts after the flowers fell down; H: Floral bract (left to right; lateral view, abaxial and adaxial) I: Flower; J: Sepals (left, adaxial; right, abaxial); K: Pistil; L: Stamens; M: Fruits, left to right lateral view. Drawings by L. Valenzuela from the Holotype LV 28745.

FIGURE 4. Polylepis rocio-rojasii. A: Trunk; B: Branch; C: Twig with some leaves (abaxial); D: Twig with 2 leaves (adaxial) and inflorescences; E: Stipular sheath; F: Trifoliolate leaf densely lanuginose (abaxial); G: Leaf sparsely lanuginose with secondary venation immersed (adaxial); H: Fruits (left, lateral view; right, top view). Images by L. Valenzuela from the Holotype LV 28745.