Polylepis pampabella H.R.Quispe, Llacua & M.Kessler

Quispe-Melgar, Harold Rusbelth, Llacua-Tineo, Yashira Stefani, Arias, Nathaly Estela Ulloa & Kessler, Michael, 2024, A new species of Polylepis (Rosaceae) from Santuario Nacional Pampa Hermosa, Peru, Phytotaxa 653 (2), pp. 165-174 : 167-172

Polylepis pampabella H.R.Quispe, Llacua & M.Kessler sp. nov. ( Figs. 2–3 )

Type: — PERU. Junín: Province Tarma, District Huasahuasi , Locality Loma Pajonal , humid high Andean forest, 11°11’57”S, 75°36’14W, 3.750 m, 30 March 2024, H.R.Quispe, Yashira Stefani Llacua Tineo and Nathaly Estela Ulloa Arias 132 (holotype HSCH!, isotypes HOXA!, Z!) .

Similar to Polylepis canoi but leaves with 1 pair of lateral leaflets, 3.4–6.3 × 3.3–7.8 cm (vs. 2–3(4) pairs of lateral leaflets, (4.0–)7.9–9.4 × (4.2–) 6.7–7.5 cm), leaflets oblong-lanceolate in outline (vs. obovate), with tufts of yellowish, stiff hairs at leaflet insertion point, with yellow reddish resin (vs. tufts of long, straight, yellowish hairs at leaflet insertion point, with ferruginous resin), inflorescences 8–14 cm long, bearing 6–13 flowers (vs. 8.2–14.5 cm long, bearing 12–17(26) flowers), and 17–23 stamens per flower (vs. 13–15). Further characterized by entire, sessile, basally unequally auriculate lateral leaflets.

Trees 3–12 m tall, with multiple branches at the base or a few meters from the ground, thin, short layers of rhytidome that peel off, orange to dark brown in color. Leaves strongly congested towards the terminal ends of the branches, imparipinnate with 1 pairs of lateral leaflets (rarely with a second pair in adults and more common in juvenile plants), obtrullate in outline, 3.4–6.3 × 3.3–7.8 cm, densely sericeous on the lower surface with hairs 1.5–2.5 mm long, upper surfaces glabrescent with few hairs in the mid-vein depression; rachis grooved, sericeous, 0.1–0.5 cm long, points of leaflet attachment with a tuft 2–3 mm of long, straight hairs, with reddish yellow resin at leaflet insertion; stipular sheaths apically acute with spurs, densely sericeous on outer surfaces, glabrous inwards; with long whitish hairs at the insertion point of the leaf; leaflets oblong lanceolate in outline, coriaceous; central leaflet 2.8–4.9 × 0.4–1 cm, apically emarginate (but appearing acute due to hairs), margin entire, attenuate; lateral leaflets 2.3–4.5 × 0.4–0.9 cm, apically emarginate (but appearing acute due to hairs), margins entire, sessile, basally unequally auriculate. Inflorescences pendant, 8–14 cm long, bearing 6–13 flowers; floral bracts 0.8–1.7× 0.2–0.3 cm, narrowly triangular, slightly sericeous to glabrescent on the outer surface; peduncle sericeous. Flowers 7.5–10 mm in diameter; sepals 3–4, rarely with a division of one of them so appearing to have 5, ovate, green, densely sericeous outside; stamens 17–24, anthers orbicular, with a dense tuft of straight white hairs from the point of insertion of the filament, 4–7 mm long; styles fimbriate, 1.5–2.8 mm long. Fruits turbinate, spines 10–15, densely sericeous, dark cherry; 2.5–6.5 × 4.5–10 mm including spines.

Distribution and ecology: — Polylepis pampabella is known from only two sites on the eastern cordillera of the central Peruvian Andes, in the department of Junín, at 3.500 –3.800 m elevation. They are part of the high Andean wet forests, forming homogeneous stands mainly at higher elevations, whereas downwards they merge with Yungas cloud forests. Within the forest patches, the soil and tree trunks are covered with mosses, lichens, ferns, fungi, and small shrubs ( Fig. 4 ). The forest matrix is surrounded by humid Puna vegetation.

Based on the two currently known records, the climatic niche of Polylepis pampabella is similar to that of Polylepis canoi , occurring at lower elevations and under warmer conditions, and in wetter areas, than P. albicans and P. argentea , two other closely related species that also are found in central Peru ( Fig. 5 ).

Paratypes: PERU. Junín: Province Chanchamayo, District Chanchamayo , Locality Quinualragra , humid high Andean forest, 11°3’8”S, 75°31’48W, 3.550 m, 12 May 2024, N.E.Ulloa Arias 1 ( HSCH!) .

Etymology: —The name is an adaptation of the Santuario Nacional Pampa Hermosa. Hermosa means beautiful in Spanish, which matches to bella in Latin (and Spanish as well).

Conservation Status:— Polylepis pampabella is currently known only from two localities in the department of Junín. We estimate that the species has 8 km 2 of area of occupancy (AOO). During field work, we observed the presence of livestock, agricultural activity, burning of pastures and forests at the locations where the species occurs. Based on this we suggest to classify the species as Critically Endangered (CR B2a).

Notes: —Seedlings and young plants of Polylepis pampabella may have a small second pair of leaflets (rare in adults) which are broader. This should be taken into account when identifying the species, as it could be confused with Polylepis canoi , especially when the distribution range of both species overlaps. Such heterophyly is also known in some other species of Polylepis , most notably in Polylepis pauta from Ecuador ( Boza Espinoza & Kessler 2022).

The discovery of a new species of Polylepis might appear to be unexpected considering the recent publication of a monographic treatment of the genus ( Boza Espinoza & Kessler 2022). However, the high rate of descriptions of new species in the last few years (e.g., Boza Espinoza et al. 2019, 2020), many of which have very small ranges, already hinted at the probability of finding further localized endemics, as in the case of the present species. Many of the new species show unique character combinations of closely related species and it might be hypothesized that they originate from hybridization events, partly coupled with polyploidization ( Schmidt-Lebuhn et al. 2006; Boza Espinoza & Kessler 2022). Polylepis pampabella occurs just at the northern range of P. canoi and it is conceivable that it evolved from hybridization of this species with a third species, but genomic studies will be necessary to confirm this.

The discovery of this species confirms that the central Peruvian Andes are a hotspot of biodiversity and endemism that remains poorly explored. In the last few years, several new species of Polylepis , including P. argentea , P.pilosissima Boza & Kessler , P. sacra Boza & Kessler , and P. fjeldsaoi Boza & Kessler , have been described from central Peru ( Boza Espinoza et al. 2019, 2020, Boza Espinoza & Kessler 2022: 158, 188 and 218) and new distributional records have been made of previously known species ( Quispe-Melgar et al. 2023a). Also, this area has a great diversity of Polylepis forest associated birds, with records of restricted-range taxa, and numerous additional new species of flora and fauna have been described (e.g., Witt & Lane 2009; Aucca et al. 2015; Quispe-Melgar et al. 2018, 2020, 2022, 2023a,b; Krabbe et al. 2020; Navarro Romo et al. 2020; Cuadros-Rojas et al. 2023). The poor biological knowledge of this region is due to the complex topography leading to small-scale endemism, difficult accessibility, in combination with security concerns that have inhibited field work from the 1980ies to the early 2000s. Considering the high human population density, this region deserves much more attention both for biological exploration and sustainable conservation.

Figures

FIGURE 2. Illustration of Polylepis pampabella. A. Flowering branch. B. Leaf, lower surfaces. C. Seedling leaves. D. Detail of the insertion point of the leaflets on the upper surface. E. Detail of the insertion point of the leaflets on the lower surface F. Flower with stamens and gynoecium G. Fruit. Drawings by Michael Kessler.

FIGURE 3. Polylepis pampabella. A. Trunk. B. Flowering branch. C–D. Leaves of adult individuals, showing upper and lower leaf surfaces. E–F. Seedling leaves, showing upper and lower leaf surfaces. Note that seedling leaflets are wider and may occasionally have an extra pair of small leaflets. Photographs and LCDP by Harold Rusbelth Quispe-Melgar.

FIGURE 4. Habit and habitat of Polylepis pampabella. a.Adult individual.b. Flowering branches.c. Panoramic view of the forest located in the locality of Quinualragra. Photographs by Yashira Stefani Llacua-Tineo (a and c) and Harold Rusbelth Quispe-Melgar (b).

FIGURE 5. Niche characterization in the environmental space based on annual mean temperature (AMT °C), annual precipitation (AP mm/year) and elevation. Box plots with different letters (a, b or c) are significantly different based on a post-hoc Tukey test.