Peru. Ancash: from Yanganuco to Yungay, 3800 m, 16 June 1903, Weberbauer 3287 (holotype: B destroyed; photos at F, GH, MO!, NY).

Trees 1–14 m tall. Leaves slightly congested at the branch tips, imparipinnate with 2–3 pairs of lateral leaflets, obtrullate in outline, (3.2–)5.2–5.8 × (2.7–)3.2–3.5 cm; rachises densely tomentose, points of leaflet attachment with a tuft of long, lanate hairs; stipular sheaths apically acute with spurs, densely lanate on the outer surfaces; leaflets elliptic in outline, second pair from the terminal leaflet the largest, one of this pair 1.6–2.1 × 0.6–0.9 cm; margin entire or slightly crenate at apex with 3–4 teeth, apically emarginate, basally unequally cordate; upper leaflet surfaces glabrous; lower leaflet surfaces densely tomentose with whitish hairs 0.4–0.5 mm long. Inflorescences pendant, 8.2–9.7 cm long, bearing 9–11 flowers; floral bracts 5.4–7.5 mm long, narrowly triangular, densely lanate on the outer surface; rachises tomentose. Flowers 8.6–10.4 mm diam.; sepals 4, ovate, green, densely tomentose outside; stamens 19–21, anthers orbicular, with a dense tuft of straight white hairs on the upper half; styles fimbriate, 2.7–3.2 mm long. Fruits turbinate, with variable numbers and placement of flattened spines, densely villous; 4.2–4.9 × 4.8–5.3 mm including spines. Diploid.

Polylepisweberbaueri is distributed in northern Peru in Ancash, Huánuco and Lima (Fig. 61). It occurs in dry and cold Andean habitats at 3500–4970 m elevation. Some stands of P.weberbaueri occur in semi-humid areas mixed with Gynoxys, Oreocallis, Alnus, Berberis and Buddleja, but it can also be found in large, homogeneous stands with dense vegetation cover and very robust trees (Sevillano-Ríos et al. 2011). It often co-occurs with P.albicans, but P.weberbaueri tends to occur at higher elevations (ECOAN 2005; Fuentealba and Sevillano 2016; Sevillano-Ríos and Rodewald 2017; Morales et al. 2018). In a study in Huascarán National Park, seedling density of P.weberbaueri increased with elevation and decreased with solar radiation (Morales et al. 2018). These forests also support the hemiparasite Tristerixchodatianus (Patschovky) Kuijt (Loranthaceae) at over 4400 m elevation (ECOAN 2005; Sevillano-Ríos et al. 2011). Polylepisweberbaueri forests at higher elevations (> 4000 m) harbor some of the most specialized and endangered bird species (Sevillano-Ríos et al. 2011; Sevillano-Ríos and Rodewald 2017).

The EOO is estimated as 15 388 km² and AOO as 224 km². The species has been collected in 39 locations. It is protected within Huascarán National Park and was categorized as VU (SERFOR 2006). It is subject to reforestation activities in Huascarán National Park (Fuentealba and Sevillano 2016). We assess P.weberbaueri as Vulnerable (B1a B2a).

Polylepisweberbaueri can be distinguished from the most similar species P.occidentalis by the number of lateral leaflet pairs (2–3 versus 3–5), inflorescence length (8.2–9.7 cm versus 2.4–6.7 cm), style length (2.7–3.2 mm versus 1.5–2.0 mm) and number of stamens (19–21 versus 9–15).

Peru. Ancash: Bolognesi, Pachapaque, Distr de Aquia, 3900 m, 01 August 1972, Cerrate 2 (USM!); entre Llamac y Jahuacocha, 4900 m, 29 May 1954, Cerrate 2314 (USM!); road from Abra Janashalla down to Huallanca, below Huansalá, 09°52'05"S, 076°59'27"W, 3390 m, 08 October 2007, Weigend 8810 (USM!). Carhuaz, Sonquenua, Shilla, 3950 m, 21 December 1989, Arce 187 (MO!); Huascarán National Park. Quebrada Ishinca, north side of valley, 09°23'S, 077°26'W, 4110–4350 m, 15 July 1985, Smith 11169 (MO!, USM!); Huascarán National Park, Quebrada Ishinca, south side of valley, 09°23'S, 077°26'W, 4200–4260 m, 17 July 1985, Smith 11236 (AAU!, F!, MO!, USM!); Huascarán National Park. Quebrada Ulta, on road to Ulta Pass, WNW-facing, steep slope, 09°08'S, 077°32'W, 4280 m, 29 July 1985, Smith 11383 (MO!, USM!); 11659 (F!, MO!, USM!); Huascarán National Park, Quebrada Ishinca, 09°22'S, 077°25'W, 4400 m, 13 February 1985, Smith 9535 (MO!, USM!); 09°23'S, 077°27'W, 4100 m, 14 February 1985, Smith 9568 (AAU!, F!, MO!, USM!). Chavin de Huantar, Cordillera Blanca, Quebrada Pucavada (road between Huaraz and Chavin, on eastern side of pass), 09°40'S, 077°15'W, 4100 m, 16 February 1987, Boertmann 62 (AAU!); 64 (AAU!). Cusca, Cordillera Blanca, Misquicyucu 20 km east of Yanac towards Sihuas, top of the pass, 08°37'S, 077°45'W, 4000 m, 20 February 1987, Boertmann 74 (AAU!). Huantar, Quebrada Carhuascancha, Cordillera Blanca, 09°29'S, 077°15'W, 3900 m, 15 August 1988, Frimer 131 (AAU!); 133 (AAU!); 134 (AAU!). Huaraz, Feria de plantas medicinales de Huaraz, 3052 m, 01 July 1988, Amaro s.n (USM!); Quebrada Pitec, 4000 m, 30 October 1989, Arce 162 (MO!); Llaca, 09°28'52"S, 077°27'42"W, 3909 m, 08 November 2014, Boza 3021 (USM!, Z!); Rajacolta, 4420 m, 06 June 2015, Boza 3148; 3149 (USM!, Z!); Ulta, 4450 m, 07 June 2015, Boza 3150; 3151 (USM!, Z!); Quebrada Shallap, Cordillera Blanca, 09°31'S, 077°24'W, 4000 m, 10 August 1988, Frimer 16; 17; 4 (AAU!); Huascarán National Park, Quebrada LLaca, NW-slope of valley, 09°27'S, 077°27'W, 4200–4400 m, 24 May 1985, Smith 10783 (MO!, USM!); Huascarán National Park, Quebrada Llaca, valley bottom and north side of valley, 09°27'S, 077°27'W, 4090 m, 13 July 1985, Smith 11143; 12432 (MO!, USM!); 8973 (AAU!, MO!, USM!); 9696 (MO!, USM!). Huari, 30 km N of Huari, 3960 m, 18 December 1979, Aronson 993 (F!, MO!); 3000 m, 15 August 1983, Basauri 3 (USM!); Cahuish, 09°41'30"S, 077°14'30"W, 4306 m, 08 November 2014, Boza 3017; 3018 (USM!, Z!); Chavín, antes del Tunel de Cahuish (Cuta Queñua), 3100–3200 m, 11 June 2002, Cano 12385 (MO!, USM!); 09°33'S, 077°10'W, 3500 m, 14 February 2006, Sayre 39 (USM!); Huascarán National Park, road to microwave tower passing Manto Mina, off Catac-Chavin road, 09°42'S, 077°15'W, 4400 m, 04 July 1985, Smith 10974 (MO!, USM!); Huascarán National Park, upper terrace, Quebrada Pachachaca a lateral valley of Quebrada Rurichinchay Bogs, 09°23'S, 077°17'W, 4040–4200 m, 13 June 1986, Smith 12586 (F!, MO!, USM!); Huascarán National Park. Catac-Chavin road, 44 km from Catac, 09°42'S, 077°13'W, 4200 m, 18 August 1984, Smith 8287 (MO!, USM!); Huascarán National Park, 0.25 km from Cahuish Tunnel, 09°41'S, 077°14'W, 4450 m, 23 December 1984, Smith 8752 (F!, MO!, USM!). Huaylas, Laguna Parón, 3860–4000 m, 15 October 1999, Cano 10023 (USM!); Quebrada Paron, Cordillera Blanca (east of L. Paron), 08°58'S, 077°38'W, 4200 m, 16 August 1988, Frimer 23; 24; 26 (AAU!); Huascarán National Park, Quebrada Parón, 09°01'S, 077°43'W, 3500–3760 m, 08 May 1985, Smith 10608 (AAU!, F!, MO!, USM!); Huascarán National Park, Parón valley E of lake, 08°59'S, 077°38'W, 4250 m, 27 September 1985, Smith 11477 (F!, MO!, USM!); Huascarán National Park. Quebrada Santa Cruz at base of and entering Quebrada Artizonraju, 08°55'S, 077°36'W, 4300–4800 m, 16 January 1985, Smith 9308 (MO!, USM!); Huascarán National Park, environs of Hatuncocha, 08°52'S, 077°45'W, 4600 m, 12 March 1985, Smith 9982 (AAU!, F!, MO!, USM!); Huascarán National Park. between Huiscash and Mirador, 08°53'S, 077°46'W, 3960–4400 m, 12 March 1985, Smith 9988 (MO!, USM!). Pomabamba, Pumacocha, 4200 m, 11 December 1989, Arce 175 (MO!); Pumacocha, 4300 m, 11 December 1989, Arce 177 (MO!); Quenuarajra, 3600 m, 12 December 1989, Arce 182 (MO!). San Marcos, San Marcos. Distr. Ccolla Chica, 09°40'28"S, 077°03'10"W, 5600 m, 04 May 2008, Beltrán 6480 (USM!). Shilla, Quebrada Matará in Quebrada Ulta, Cordillera Blanca, 09°07'S, 077°32'W, 4250 m, 03 September 1988, Frimer 105; 106; 114 (AAU!). Sihuas, Distr. Cashapampa, Pasacancha, 08°35'01"S, 077°39'09"W, 3972 m, 03 February 2011, Gonzáles 1423 (USM!). Tarica, Quebrada Ishinca, Cordillera Blanca, 09°23'S, 077°28'W, 3950 m, 23 August 1988, Frimer 72 (AAU!). Yungay, Yanama, 3950 m, 05 November 1989, Arce 166 (MO!); Llanganuco, fuera del parque Huascarán, 3500 m, 29 May 1981, Cerrate 7769 (USM!); ca. 25 km NE of Yungay, slopes below Laguna de Llanganuco, 3380 m, 28 January 1983, Dillon 3117 (F!, MO!, USM!); slopes below Laguna de Llanganuco in quebrada de Llanganuco ca. 25 km above Yungay, 3900 m, 27 June 1966, Edwin 3829 (F!); Llanganuco, 3700–3800 m, 02 May 1961, Ferreyra 14377 (GOET!, MO!, USM!); 37 km east of Yungay, 4200 m, 05 April 1988, Renvoize 5084 (AAU!, MO!); Huascarán National Park, Llanganuco sector, Quebrada Demanda, side valley to Nevado Pisco, 09°01'S, 077°37'W, 4600–4800 m, 13 April 1985, Smith 10299 (MO!, USM!); Smith 8794 (MO!, USM!); Huascarán National Park. Quebrada Ranincuray, 08°59'S, 077°34'W, 4000–4300 m, 12 January 1985, Smith 9139 (AAU!, MO!, USM!). 4000 m, 24 August 1977, Antunez de Mayolo 330 (MO!, USM!); Cordillera Blanca, East of Yungay Lagunas de Llanganuco lake side, 3800 m, 05 April 1988, Renvoize 5067 (AAU!); 16 June 1903, Weberbauer 3287 (B, MO!). Huánuco: Huallanca, Huansala 10 km from Huallanca, 09°51'S, 076°56'W, 3700 m, 14 February 1987, Boertmann 48 (AAU!). Lima: Cajatambo, Cerro San Cristobal, 3950 m, 12 March 1990, Arce 206 (MO!); Raura, 4600 m, 05 April 1988, Rivas s.n (USM!). Oyon, Laguna Guengue Grande, Quichas, 4200 m, 11 January 1990, Arce 190 (MO!); Pueblo Quichas above Oyon, 10°36'S, 076°45'W, 4000 m, 26 February 1987, Boertmann 81; 82; 85; 87 (AAU!); Oyon, Laguna grande, 10°33'48"S, 076°44'25"W, 4005 m, 24 May 2015, Boza 3026; 3047; 3048; 3049; 3050; 3051; 3052; 3053; 3054; 3055; 3056; 3057 (USM!, Z!); Bosque de Polylepis de Maticuna, 10°39'11"S, 076°50'21"W, 3990 m, 08 August 1998, Mendoza 173 (CUZ!). Ticlayan, Quichas, Bosque de Polylepis de Q’asacancha, 10°33'S, 076°04'W, 4200 m, 07 July 1998, Mendoza 170 (CUZ!).