Polylepis acomayensis T.Boza & M.Kessler, 2022

Boza Espinoza, Tatiana Erika & Kessler, Michael, 2022, A monograph of the genus Polylepis (Rosaceae), PhytoKeys 203, pp. 1-274 : 1

28. Polylepis acomayensis T.Boza & M.Kessler sp. nov.

Figs 77 , 78

Diagnosis.

This species differs from P. triacontandra Bitter by its smaller leaflets with different type and length of hairs and shorter inflorescences with lower number of flowers.

Type.

Peru. Cusco: Acomayo. Rondocan, bosque de Llamacocha, 13°50'34"S, 072°02'31"W, 3933 m, 12 Jul 2015, T.E. Boza E. & E. Urquiaga 3038 (holotype: USM!; isotype: Z!) .

Description.

Trees 3-8 m tall. Leaves slightly congested at the branch tips, imparipinnate with 1(-2) pair of leaflets, obtrullate in outline, (2.7-)3.5-4.5 × 2.6-3.3 cm; rachises densely villous, points of leaflet attachment with a tuft of long hairs; stipular sheaths apically truncate, densely villous on the outer surfaces; leaflets narrowly obovate in outline, second pair from the terminal leaflet the largest, one of this pair 1.6-2.3 × 0.5-0.9 cm; margin crenate with 6-9 teeth, apically round or emarginate, basally acute; upper leaflet surfaces sparsely villous; lower leaflet surfaces densely villous with whitish hairs 0.9-1.1 mm long mixed with pannose hairs, second pair of leaflets, if present, very small. Inflorescences pendant, 2.0-4.0 cm long, bearing 5-7 flowers; floral bracts 3.9-4.2 mm long, narrowly triangular, densely villous on the outer surface; rachises villous. Flowers 10.2-10.7 mm diam.; sepals 4, ovate, green, densely villous outside; stamens 19-25, anthers orbicular, with a dense tuft of straight white hairs on the upper half; styles fimbriate, 2.3-4.0 mm long. Fruits turbinate, with 2-3 irregular flattened ridges with a series of spines, densely villous; 4.2-5.7 × 3.2-4.4 mm including spines. Tetraploid.

Distribution, habitat and ecology.

Polylepis acomayensis occurs in southern Cusco (Peru) in relatively cold and dry Andes at 3800-4160 m elevation (Fig. 92 ). It grows in mixed forests with Escallonia resinosa .

Etymology.

This species is named after Acomayo, the Province to which its distribution appears to be restricted.

Conservation status.

The EOO for Polylepis acomayensis is estimated as 110 km2, the AOO is assessed at 12 km2 and it is known only from three locations. The species is unprotected. Logging, grazing and agriculture are the most important activities affecting these forests. We assess P. acomayensis as Endangered (A2a, B1a+B2a, C2a).

Notes.

Polylepis acomayensis resembles P. triacontandra in having 1(-2) lateral leaflets pairs as well as similar leaflet margin and density of hairs. However, it has narrowly obovate leaflets 1.6-2.3 × 0.5-0.9 cm long with villous hairs 0.9-1.1 mm long and inflorescences 2.0-4.0 cm long with 5-7 flowers, whereas P. triacontandra has narrowly elliptic leaflets (2.0-)2.6-3.3 × 0.7-1.1 cm long with tomentose hairs 0.4-0.8 mm long and inflorescences 4.9-9.5 cm long with 11-13 flowers. Polylepis acomayensis is also morphologically similar to P. sacra with which it shares similar leaflet size, margin and hair density. The most obvious differences between P. acomayensis and this species are the number of lateral leaflet pairs, with P. acomayensis having 1(-2) pairs, whereas P. sacra has 2-3 pairs. Furthermore, P. acomayensis has villous hairs 0.9-1.1 mm long and inflorescences 2.0-4.0 cm long whereas P. sacra has lanate hairs 1.3-1.5 mm long and inflorescences 5.0-8.8 cm long.

Specimens examined.

Peru. Cusco: Acomayo, Rondocan, Llamacocha , 13°50'53.6"S, 71°45'32.7"W, 3933 m, 12 July 2015, Boza & Urquiaga 3038; 3122; 3123; 3124; 3125; 3126; 3127; 3128; 3129; 3130; 3131; 3132 (USM!, Z!). Paruro, Accha, Kangal, 13°59'41.2"S, 71°48'42.3"W, 4194 m, 12 July 2015, Boza & Urquiaga 3039; 3133; 3134; 3135; 3136; 3137; 3138; 3139; 3140; 3141; 3142; 3143 (USM!, Z!) .

Figures

Figure 77. Polylepis acomayensis T. Boza & M. Kessler A flowering branch B upper leaf surface C lower leaf surface D fruits E stipular sheaths F flowers (B Boza & Urquiaga 3038 A, C, D, E, F Boza & Urquiaga 3039). Scale bars: 1 cm (A-C); 5 mm (D, F); 2 mm (E). Photographs A, D, E, F T. E. Boza E. B, C E. G. Urquiaga F.

Figure 78. Polylepis acomayensis T. Boza & M. Kessler A flowering branch B upper leaf surface C lower leaf surface D stipular sheaths E lower leaf surface F upper leaf surface G fruits (A, D, G Boza 3135 B, C Boza 3039 E, F Boza 3133). Scale bars: 7 cm (A); 3 cm (B, C); 2 cm (E, F); 7 mm (G). Photographs by E. G. Urquiaga F.

Figure 92. Geographical distribution of the species of subsection Polylepis Racemosae Racemosae.