Resumen

The upper elevations (2300-4200m) of a national park located on the eastern slopes of the northern Peruvian Andes were surveyed for their pteridophyte flora. A total of 174 species in 43 genera were found. The most diverse ecological zone was the montaine rain forest zone located from 3100m upwards to timberline, which contained 109 pteridophyte species. This was high species richness compared to adjacent ecological zones: tropical alpine, 65 species; montane wet forest, 61 species. We suggest that the reasons for this were a high and constant humidity, the abundance of speciose genera such as Elaphoglossum, and the sharing of species with both of the adjacent zones