Peru. Ancash: Cordillera Blanca above Caraz, Jun 1903, Weberbauer 3229 (holotype: B destroyed; photos at F!, GH!, NY!).

Trees 3–7(12) m tall. Leaves strongly congested at the branch tips, imparipinnate with 3–4 pairs of lateral leaflets, obtrullate in outline, 3.5–4.9 × (2.5–)2.8–3.4 cm; rachises densely sericeous, points of leaflet attachment with a tuft of long, straight hairs, with ferruginous resin at leaflet insertion; stipular sheaths apically acute with spurs, densely sericeous on the outer surfaces; leaflets elliptic in outline, second pair from the terminal leaflet the largest, one of this pair 1.4–2.0 × 0.4–0.7 cm; margin slightly crenate at the apex with 4–5 teeth, strongly revolute, coriaceous, apically emarginate, basally unequally cordate; upper leaflet surfaces glabrous or sparsely sericeous; lower leaflet surfaces densely sericeous with short silky hairs 0.3–0.5 mm long. Inflorescences pendant, 3.9–6.6(7.5) cm long, bearing 18–21 flowers; floral bracts 5.5–6.9 mm long, narrowly triangular, densely sericeous on the outer surface; rachises sericeous. Flowers 3.4–7.5 mm diam.; sepals 3–4, ovate, green, densely sericeous outside; stamens 7–18, anthers orbicular, with a dense tuft of straight white hairs on the upper half; styles fimbriate, 1.4–3.2 mm long. Fruits turbinate, with variable numbers and placement of flattened spines, densely sericeous; 3.1–5.6 × 2.3–5.6 mm including spines. Diploid.

Polylepisalbicans occurs in north-western Peru in the Cordillera Blanca in Ancash and in the adjacent high Andes of La Libertad (Fig. 41). It grows in semi-humid montane forest at 3400–4950 m elevation, often alongside P.weberbaueri (Fig. 41). Where they co-occur, P.albicans tends to grow at lower elevations (maximum probability of occurrence at 3750–3900 m) than P.weberbaueri (4400 m) (Morales et al. 2018) and to generally grow in warmer and drier habitats than P.weberbaueri (Sevillano-Ríos and Morales 2021). Along with this, seedling density of P.albicans decreases with elevation, whereas that of P.weberbaueri increases (Morales et al. 2018). At 4350–4700 m elev. in Paria Valley, most trees of P.albicans are 4–7 m tall (maximum 10–12.5 m) with diameters of 10–20 cm (maximum 50–60 cm) (Castro and Flores 2015). The Polylepis forests in this region harbor diverse bird communities with a substantial proportion of threatened species, some of which are specialized to Polylepis forests (Sevillano-Ríos et al. 2011; Sevillano-Ríos and Rodewald 2017, 2021).

The Extent of Occurrence (EOO) for P.albicans is estimated as 13,028 km², the area of occupancy (AOO) is assessed at 164 km² and it is known from 24 locations. It occurs in Huascarán National Park which encompasses almost the entire Cordillera Blanca. However, illegal mining occurs within the Park, becoming a direct threat to the species. Polylepisalbicans is subject to reforestation activities in Huascarán National Park (Fuentealba and Sevillano 2016). We assess the species as Vulnerable (B1a+B2a).

This species was described by Pilger (1906), based on material from Caraz, Cordillera Blanca, Peru. It was synonymized under P.sericea by Simpson (1979) who mentioned that populations of P.sericea from the Cordillera Blanca are distinct by having leaflets with pronounced pubescence in both sides. Based on its distinct morphology and ecology, this taxon was re-instated at species level by Boza Espinoza et al. (2019). Polylepisalbicans differs from P.sericea by a sparse to dense sericeous hair cover on the upper leaflet surfaces and on the leaf rachises (versus glabrous in both cases in P.sericea), shorter hairs (0.3–0.5 mm versus 0.7–1.0 mm) and commonly reddish glandular hairs at leaflet bases (lacking in P.sericea). Occasionally, specimens of P.albicans resemble those of P.argentea in leaflet shape, but leaflet margins are slightly crenate in P.albicans and entire in P.argentea. Further, P.argentea differs from P.albicans by the lower number of flowers in the inflorescence (5–9 versus 18–21).

To us, the reddish glands, thick leaf texture and often emarginated leaflet apices suggest that P.albicans may include some genetic elements from P.weberbaueri, with which it co-occurs, but this remains to be tested by molecular studies.

Peru. Ancash: Carhuaz, Sonquenua, Shilla, 4020 m, 21 December 1989, Arce & Sánchez 188 (MO); Valley of Río Marcará, 2.5 hours from Vicos on trail to Lejiacocha, 09°19'00"S, 077°31'00"W, 3600 m, 11 March 1964, Hutchison & Wright 4325 (F, MO, USM); Shacshicucho, 4050 m, 26 August 1978, Mostacero et al. 569 (MO); Huascarán National Park; Quebrada Ulta, north side of valley; S-facing, moderate to gentle slopes, 09°07'S,077°32'W, 3930 m, 29 July 1985, Smith 11410 (MO, USM); Huascarán National Park. N-side of main valley, Quebrada Honda, 09°18'S, 077°25'W, 4200 m, 03 October 1985, Smith et al. 11641 (F, MO, USM); Huascarán National Park, mouth of Quebrada Ishinca, 09°23'S, 077°29'W, 3880 m, 15 February 1985, Smith et al. 9597 (F, MO, USM). Huaraz, Quebrada Quillcayhuanca, 4200 m, 30 October 1989, Arce & Martel 163 (MO); Quilcayhuanca, 09° 29'53.8"S, 77°24'59.6"W, 3831 m, 08 November 2014, Boza & Urquiaga 3022 (USM, Z); Lance, 4500 m, 04 June 2015, Boza &Urquiaga 3144 (USM, Z); Llanganuco, 09°04'47"S, 077°38'36"W, 4445 m, 03 June 2015, Boza & Urquiaga 3145 (USM, Z); 3146 (USM, Z); 3147 (USM, Z); Ulta, 09°06'S, 077°32'W, 4300 m, 07 June 2015, Boza & Urquiaga 3152 (USM, Z); 3153 (USM, Z); Llaca, 09°26'S, 077°26'W, 07 June 2015, Boza & Urquiaga 3154 (USM, Z); 3155 (USM, Z); Boza & Urquiaga 3156 (USM, Z); 28 May 1982, Cerrate 7696 (MO, USM); Comprado en la feria de plantas medicinales de Huaraz, 07 July 1988, Cerrate 9123 (USM); Huascarán National Park, Quebrada Shallap, 09°30'S, 077°24'W, 3900 m, 20 February 1985, Smith et al. 9709 (F, MO, USM). Huari, Llanganuco, 4366 m, 29 November 2007, Lasermann I12 (USM); Huascarán National Park, southside of Quebrada Carhuazcancha, 09°28'S, 077°15'W, 4200 m, 06 May 1986, Smith et al. 12255 (MO, USM); Huascarán National Park, Quebrada Pachachaca, a lateral valley of Quebrada Rurichinchay, 09°27'S, 077°16'W, 3860 m, 12 June 1986, Smith et al. 12542 (F, MO); Huascarán National Park, Quebrada de Yuraccocha, a lateral valley of Quebrada Rurichinchay, 09°22'S, 077°17'W, 4300 m, 16 June 1986, Smith et al. 12737 (MO, USM); Acopalca, 09°20'25"S, 077°12'19"W, 3300 m, 11 August 2010, Xue-Jun 194 (USM). Huaylas, Paron, 09°02'13"S, 77°43'52"W, 3357 m, 07 November 2014, Boza & Urquiaga 3016 (USM, Z); Huascarán National Park, Quebrada Parón, 09°01'S, 077°43'W, 3760 m, 08 May 1985, Smith 10606 (MO); Huascarán National Park, 09°00'S, 077°41'W, 4200 m, 29 September 1985, Smith 11537 (MO, USM); Huascarán National Park, Parón Valley, 09°00'S, 077°42'W, 4150 m, 01 January 1985, Smith & Goodwin 8924 (AAU, F, MO, USM); Huascarán National Park, Parón Valley, 09°01'S, 077°43'W, 3700 m, 01 January 1985, Smith & Goodwin 8939 (MO, USM); Huascarán National Park, western flank of Cordillera Blanca, Alpamayo–Cashapampa trail, 08°53'S, 077°45'W, 3950 m, 13 March 1985, Smith & Valencia 10013 (MO, USM); Huascarán National Park, lower slopes of Cerro Pakla, 08°49'S, 077°57'W, 4300 m, 09 April 1986, Smith et al. 12055 (AAU, F, MO, USM); Huascarán National Park, Quebrada Santa Cruz at base of and entering Quebrada Artizonraju, 08°55'S, 077°36'W, 4800 m, 16 January 1985, Smith et al. 9298 (F, MO, USM). Yungay, Ruta Vaqueria–Portachuelo, 3900 m, 05 November 1989, Arce 165 (MO); Huaytajirca, en el Dist. de Yanama, procedencia Matca (Yanama), 16 December 1989, Arce & Abilio 186 (MO); 30 km, hacia arriba, Parque Nacional de Huascaran, 3850 m, 10 March 1983, Beck 7914 (GOET, MO); Llanganuco, 09°03'04"S, 77°36'42"W, 3852 m, 07 November 2014, Boza & Urquiaga 3013 (USM, Z); Llanganuco encima de Yungay, 4000 m, 27 June 1966, Ferreyra 16860 (MO); Llanganuco arriba de Yungay, 4200 m, 14 December 1967, Ferreyra & Blount 18727 (GOET, MO, USM); Llanganuco, arriba de Yungay, 3900 m, 22 October 1965, Ferreyra & Tryon 16503 (MO, USM); slopes below Laguna de LLanganuco in quebrada de Llanganuco ca. 25 km above Yungay, just above and below the lake, 4100 m, 27 June 1966, Gabriel & Schunke 3826 (A, F); Dist. Yungay, Laguna de Llanganuco, 3800 m, 17 February 1968, Gutiérrez 249 (F); Laguna de Llanganuco, 3800 m, 19 February 1968, Gutiérrez 249-AGR (MO); Quebrada Llanganuco, cerca de la laguna y el albergue, 3850 m, 04 July 1981, Peréz 62 (USM); Laguna Llanganuco, 3400 m, 01 November 1984, Sagástegui & Dillon 12315 (F, MO); near Laguna Llanganuco, 09°03'54"S, 077°38'00"W, 4300 m, 14 August 2002, Schmidt-Lebuhn 507 (USM); near laguna Llanganuco, 09°03'54"S, 077°38'00"W, 4300 m, 14 August 2002, Schmidt-Lebuhn 510 (USM); Huascarán National Park, Lake Llanganuco, 09°05'S, 077°39'W, 3860 m, 16 August 1984, Smith 8210 (MO); Huascarán National Park, Llanganuco sector, Quebrada Demanada, side valley to Nevado Pisco, 09°02'S, 077°37'W, 4250 m, 13 April 1985, Smith & Cautivo 10302 (MO, USM); Huascarán National Park, Quebrada Ranincuray, 09°00'S, 077°33'W, 3850 m, 11 January 1985, Smith et al. 9049 (AAU, F, MO, USM); Huascarán National Park, Morococha at largest lake, 08°55'S, 077°35'W, 4550 m, 14 January 1985, Smith et al. 9215 (AAU, F, MO, USM); Llanganuco P. N. Huascarán, 09°07'00"S, 077°37'00"W, 3475 m, 07 August 2010, Xue-Jun 25 (USM). Cordillera Blanca near Ingenio in upper Pumapampa Valley, 11°04'S, 077°36'W, 4350 m, 15 February 1987, Boertmann 53 (AAU); Quebrada Ishinca, Cordillera Blanca, 09°23'S, 077°28'W, 3950 m, 23 August 1988, Frimer & Nielsen 101 (AAU); Quebrada Matará in Quebrada Ulta, Cordillera Blanca, 09°07'S, 077°32'W, 4250 m, 03 September 1988, Frimer & Nielsen 104 (AAU); Quebrada Ulta, Cordillera Blanca, 09°06'S, 077°32'W, 4050 m, 02 September 1988, Frimer & Nielsen 107 (AAU); 108 (AAU); Quebrada Rurichinchay, Cordillera Blanca, 09°21'S, 077°18'W, 4000 m, 06 Oct 1988, Frimer & Nielsen 118 (AAU); 123 (AAU); Quebrada Rurec, Cordillera Blanca, 09°25'S, 077°17'W, 3950 m, 11 October 1988, Frimer & Nielsen 125 (AAU); Frimer & Nielsen 126 (AAU); Quebrada Carhuasccancha. Cordillera Blanca, 09°29'S, 077°15'W, 3900 m, 15 October 1988, Frimer & Nielsen 132 (AAU); Querada Paron, Cordillera Blanca (W of Paron), 09°00'S, 077°41'W, 4150 m, 18 August 1988, Frimer & Nielsen 42; 43; 44; 45; 59 (AAU); Quebrada Ishinca, Cordillera Blanca, 09°23'S, 077°28'W, 3950 m, 23 August 1988, Frimer & Nielsen 70; 71; 73 (AAU); Quebrada Ishinca, Cordillera Blanca, 09°23'S, 077°28'W, 3950 m, 23 August 1988, Frimer & Nielsen 74; 99 (AAU); road from Yungay to Yauya, vicinity of Lagunas Llanganuco, 09°02'S, 077°35'W, 3800 m, 10 July 1982, Gentry et al. 37376 (MO, USM); Llanganuco, 4377 m, 29 November 2007, Lasermann II/1 (USM); Cordillera Blanca, Laguna Paron, 30 km NE of Caraz in northern Huascaran National Park, 4100 m, 10 October 1988, Peterson s.n (MO); Cordillera Blanca, East of Yungay, Laguna de Llanganuco, 3800 m, 05 April 1988, Renvoize & Lægaard 5066 (AAU); Cordillera Blanca. 35 km east of Yungay, 4000 m, 05 April 1988, Renvoize & Lægaard 5074 (AAU, MO); 5075 (AAU); 40 km east of Yungay., 4350 m, 05 April 1988, Renvoize & Lægaard 5088A; 5088B (AAU); Llanganuco Valley, 09°00'S, 077°30'W, 1500 m, August 1959, Tothill 174 (F); 3700 m, 1901–1929, Weberbauer 3229 (B, MO); Parque Nacional Huascarán. Llanganuco, 11 July 1982, Zardini 1535 (MO). La Libertad: Sánchez Carrión, señal Huayllides, 07°53'S, 078°02'W, 4100 m, 21 August 1982, Smith 2278 (MO, USM).