Polylepis yanesha L. Valenz. & T. Boza, 2025

Polylepis yanesha L. Valenz. & T. Boza sp. nov.

Type:— PERU. Pasco Region, Prov. Oxapampa, Dist. Huancabamba, Peasant Community of Santa Bárbara , Yanachaga Chemillén National Park buffer zone, Humid Puna Forest 3850 m, S10°25’55.99” 75°42’56.49”W, 12 August 2024. L. Valenzuela, T. Aronson, R. Zehnder, M. Aquino, C. Romero y A. Alanya. 38648 ( holotype HOXA!; GoogleMaps isotypes MO!, USM) GoogleMaps . Figures 1–6 View FIGURE 1 View FIGURE 2 View FIGURE 3 View FIGURE 4 View FIGURE 5 View FIGURE 6

Diagnosis:— Polylepis yanesha is similar to Polylepis rocio-rojasii but it differs because it presents the trunks with short thin papyraceous rhytidomes ( vs long and thick); central leaflet 2.9–4.0 × 0.6–0.8 cm, tridentate emarginate, lanuginose abaxial surface with filiform glandular trichomes ( vs 3.0–4.5 × 0.8–1.3 cm, bidentate emarginate, lanuginose abaxial surface without glandular trichomes); inflorescences, semi-pendulous, rigid with 5–8 flowers and 18–19 stamens per flower ( vs pendulous, rigid with 6–12 flowers and 6–18 stamens per flower); fruits achenes 3.0–3.2 × 3.3–3.5 mm rounded-ovoid or 4.0–4.2 × 1.7–1.8 mm cylindrical lanuginose with 7–8 short spines ( vs 3.0–3.5 × 2.8–3.2 mm rounded to ovoid, indehiscent, lanuginose with 1–7 short spines) ( Table 1 View TABLE 1 & Figure 6 View FIGURE 6 ).

Description: — Trees, 7–15 m tall; trunks somewhat twisted, not cracked, with short, thin, papyraceous rhytidomes, dark brown to reddish brown. Leaves (2.8)3.6–5.0(5.9) × (2.0)3.3–4.6(5.2) cm, imparipinnate, irregularly clustered towards the ends of the twigs, obovate, trifoliolate; leaflets, oblong-elliptic, dark green adaxial surface, sparsely lanuginose with bright yellow trichomes, densely lanuginose towards the abaxial surface, with filiform glandular trichomes of yellowish-gold resin, tridentate emarginate apex; stipular sheath 3.0 × 0.8 cm long tubular-cylindrical with 2 frequently persistent spurs, the sheath covered by a lanuginose indument 2.5–3.0 mm long towards the outer face, completely glabrous towards the inner face, this indument being more abundant in the sheaths of young twigs; central leaflet (2.3)2.9–4.0(4.6) × 0.6–0.8(0.9) cm, oblong-elliptic with entire margin, secondary venation inconspicuous, base obtuse, symmetrical; the petiolule is short, 2.0–3.0 × 1.7–1.8 mm, lanuginose, with a tuft of somewhat stiff trichomes towards the adaxial surface, 2.0 mm long, located at the junction with the petiole; lateral leaflets (1.6)2.4–3.4(3.9) × 0.6–0.8(0.9) cm, divergent between 30–45°, oblong-elliptic, emarginate, entire edge, sessile, asymmetric bases with inconspicuous printed secondary venation, articulated to the lanuginose grooved petiole of 0.7–1.0 × 0.12 cm, with scarce filiform glandular trichomes of yellowish golden resin, in addition 2 tufts of stiff trichomes of 2 mm length are observed, towards the adaxial surface, at the insertion of the petiole to the twig. Inflorescences 4.0–8.0 × 0.12–0.15 cm long, axillary, lanuginose, semi-pendulous, and rigid; peduncle 2.1 × 0.7 cm long, cylindrical with 1 bract, oblong-lanceolate, concave, densely lanuginose towards the outer face; floral bracts 5–8, concave cymbiform or elliptic lanceolate, densely lanuginose outer side, 8.2–8.3 × 1.2–1.3 mm long, glabrous inner side. Flowers 5–8, 8.0– 8.5 mm in diameter; pedicel 0.04–0.06 × 0.08 mm long, cylindrical, short, lanuginose, covered with unicellular trichomes, golden yellow; sepals 3–4, mostly 4, concave cymbiform, densely lanuginose outer side, and regularly glabrous inner side, the first pair 4.2 × 2.2 mm long and the second pair, thinner, 4.0 × 1.7 mm long; stamens 18–19, with orbicular lanuginose dorsifixed anthers 1.0– 1.2 mm in the smallest and 1.2–1.8 mm long in the largest, the filaments in the stamens are purple, cylindrical, and glabrous, 1.2–3.0 mm long; the style 1.8–2.0 mm long; ovaries 2.0 mm long, inferiorly lanuginose with a glabrous base; the stigma is 3.0 x 2.0 mm in diameter, fimbriated with small lamellae. Fruits in achenes 3.0–3.2 × 3.3–3.5 mm long, rounded-ovoid or 4.0–4.2 × 1.7–1.8 mm long, cylindrical, indehiscent, densely lanuginose with 7–8 short blunt spines, with a single seed.

Distribution and ecology:— Polylepis yanesha is only known from the Humid Puna forests of the Santa Bárbara Peasant Community, in the BIOAY, between 3700–3900 m elevation. It occurs on rocky environments in high mountains, very close to the cliffs exposed to strong winds, rains, and constant fogs. It grows mixed with grasses, especially with Jarava ichu Ruiz & Pavón (1798: 2) . On the other hand, it is found growing alongside other tree species of Escallonia myrtilloides Linnaeus (1781: 156) , Ilex sessiliflora Triana & Planchón (1872: 378) , Saracha punctata Ruiz & Pavón (1799: 42) , Symplocos robinfosteri Ståhl (1993: 377) , and some shrubs such as Diplostephium lechleri Weddell (1855: 204) , Epidendrum frutex Reichenbach (1855: 95) . Also, it is possible to find in their branches an epiphytic orchid Epidendrum micro-cattleya Schlechter (1921: 150) , 10–20 cm in size with bright fuchsia flowers, endemic to the Central Peruvian Rainforest. We believe that these species could be useful in the restoration of local Polylepis relict forests (Ridbäck 2008; Valenzuela & Villalba 2024).

Polylepis yanesha is currently threatened mainly by anthropogenic activities such as forest burning and the expansion of areas for grazing, which inevitably produce an irreversible reduction of the small forest remnants where the species is found. On the other hand, when performing a quick count of adult individuals, its population is less than 100 in an area of approximately 2 Km 2. It is also important to mention that so far it is the only locality and population found. Therefore, according to the International Union for Conservation of Nature, the species is probably critically endangered (CR) under criteria B2ac (ii, iv) (IUCN 2025).

Etymology:—This species is named after the Yánesha people, who inhabit the Pichis and Palcazú river basins in the BIOAY. It is essential to recognize their deep knowledge of the region’s flora and fauna in the Central Amazonian Despite the numerous challenges they faced during colonization in the 20th century, they have managed to preserve their traditions, language, and ancestral practices, reflecting the rich cultural diversity of Peru today.

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

The species P. yanesha may be confused with P. rocio-rojasii and P. pampabella . To distinguish them, see Table 1 View TABLE 1 .

Polylepis yanesha is very similar to P.rocio-rojasii in the number, shape and the abaxial leaflet surface indumentum, but it differs because the leaves are relatively smaller and obovate 3.6–5.0 × 3.3–4.6 cm ( vs simple triangular 5.0–6.0 × 6.5–6.8 cm); channeled petiole 0.7–1.0 × 0.12 cm, smaller and thinner lanuginose with glandular, filiform trichomes of golden-yellowish resin, with a tuft of stiff trichomes 2 mm long at the insertion of the petiole to the twig ( vs a little bigger and thicker 0.7–1.2 × 0.2 cm long, with a tuft of stiff trichomes 2.4–2.7 mm long at the insertion of the petiole to the twig, without glandular trichomes); stipular sheath, tubular-cylindrical, much larger than 3.0 × 0.8 cm, with 2 persistent spurs, covered by sericeous indumentum 2.5–3.0 mm long towards the outer surface, glabrous towards the inner surface ( vs smaller 2.2–2.3 × 0.4–0.5 cm, with 3 deciduous spurs, covered by sericeous indumentum 3.0–4.0 mm long on both sides); central leaflet 2.9–4.0 × 0.6–0.8 cm, oblong-elliptic, the abaxial surface densely lanuginose, with glandular, filiform trichomes of golden-yellowish resin, apex emarginate tridentate, adaxial surface with inconspicuous printed secondary venation, base obtuse, symmetrical (central leaflet 3.5–4.5 × 0.8–1.3 cm, apex emarginate bidentate, oblong-elliptic to obovate-elliptic, densely lanuginose without glandular trichomes, with the margin entire, adaxial surface with the secondary venation strongly impressed conspicuous, base obtuse symmetrical); lateral leaflets 2.4–3.4 × 0.6–0.8 cm, diverging at 30–45°, adaxial surface with inconspicuous impressed secondary venation (vs. lateral leaflets 3.0–4.5 × 0.8–1.0 cm, diverging at 75–90°, adaxial surface with very conspicuous appressed secondary venation) ( Figures 6C & 6D View FIGURE 6 ); 5–8 floral bracts 8.2–8.3 × 1.2–1.3 mm, concave-cymbiform, densely lanuginose towards the outer surface, glabrous towards the inner surface ( vs 6–12 floral bracts 7.0–9.0 × 2.2–2.7 mm, concave, ovate-elliptic, densely sericeous towards the outer surface); sepals 4, concave-cymbiform, densely lanuginous on the outer surface and regularly glabrous towards the inner surface, the first pair 4.2 x 2.2 mm and the second pair a little thinner, 4.0 × 1.7 mm long (vs. 3–4 sepals, triangular ovoid, erect, concave, 4.0–5.0 × 3.6–4.8 mm long.); gynoecium, much larger than 5.2–5.3 mm in length ( vs 4.0– 4.2 mm long).

On the other hand P. yanesha also resembles P. pampabella in the number of leaflets, but they differs by the trunks have short, thin rhytidomes that are dark brown to reddish brown ( vs long, thin, brown orange to dark brown rhytidomes); the leaves are obovate with 1 pair of leaflets ( vs orbicular-obovate with 1–2 pairs of leaflets); channeled petiole 0.7–1.0 × 0.12 cm, lanuginose with glandular filiform trichomes of golden-yellow resin, with a tuft of stiff trichomes, 2 mm long, at the insertion of the petiole to the twig ( vs channeled petiole 0.5–1.5 cm long, sericeous with glandular reddish-yellow resin trichomes, with a tuft of stiff trichomes 2–3 mm long at the insertion of the petiole to the twig); leaflets, oblong-elliptic, lanuginose towards the abaxial surface, with filiform glandular trichomes of yellowish-gold resin, tridentate emarginate apex ( vs oblong-lanceolate, densely sericeous towards the abaxial surface without glandular trichomes, acute emarginate apex); central leaflet 2.9–4.0 × 0.6–0.8 cm, oblong-elliptic, adaxial surface sparsely lanuginose, base obtuse and symmetrical ( vs central leaflet 2.8–4.9 × 0.4–1 cm, oblong-lanceolate, light olive green glabrescent adaxial surface, symmetrical attenuated base); lateral leaflets 2.4–3.4 × 0.6–0.8 cm, divergent at 30–45°, sessile and with asymmetric bases ( vs lateral leaflets 2.3–4.5 × 0.4–0.9 cm, divergent at 65–85°, sessile, asymmetrical, strongly auriculate) ( Figures 6A–6C View FIGURE 6 ); inflorescence, axillary 4.0–8.0 cm long, lanuginose, semi-pendulous, rigid, lanuginose peduncle with 5–8 flowers ( vs inflorescences, pendulous, 8–14 cm long, sericeous peduncle with 6–13 flowers); floral bracts, concave-cymbiform, 8.2–8.3 × 1.2–1.3 mm, densely lanuginose towards the outer surface ( vs floral bracts 8.0–17.0 × 2.0–3.0 mm, narrowly triangular, slightly sericeous to glabrescent on the outer surface); sepals 3–4, mostly 4, concave-cymbiform, densely lanuginose on the outer surface ( vs sepals 3–4, rarely 5 ovate, densely sericeous on the outer surface); style, fimbriated 1.8–2.0 mm long ( vs 1.5–2.8 mm long); fruits 3.0–3.2 × 3.3–3.5 mm rounded-ovoid or 4.0–4.2 × 1.7–1.8 mm cylindrical, densely lanuginose, with 7–8 short spines, with a blunt apex ( vs fruits, turbinate 2.5–6.5 × 4.5–10 mm, densely sericeous with 10–15 pointed spines).

The morphological characters presented are support the recognition of the new species described here; the discovery of this species suggests that there are still many remote and inaccessible areas to explore. In the Central Peruvian Amazonian, there are an estimated 9,000 species vascular plants, representing approximately 43% of all plants in the country ( TROPICOS 2025). This figure is even more relevant considering that this genus often has restricted distribution ranges ( Boza Espinoza & Kessler 2022).

The discovery of P. yanesha confirms that the Peruvian Central Andes are a biodiversity and endemism hotspot that still require exhaustive study ( Boza Espinoza et al. 2019; Boza Espinoza & Kessler 2022). In addition, this discovery allows us to explore deeper into Polylepis diversity and distribution in the region. It is essential to develop more ecological studies to advance conservation and restoration processes since these habitats are home to certain specific taxa, mainly birds ( Fjeldså 1987; Schulenberg et al. 2007).