Applying the IUCN Red List criteria to small-sized plants on oceanic islands: conservation implications for threatened bryophytes in the Canary Islands

Abstract

The International Union for Conservation of Nature (IUCN) Red List categories and criteria were applied to small-sized spore-producing plants with high dispersal capacities (bryophytes). The application of some of the IUCN criteria to bryophytes in small and highly environmental diverse islands implies several problems. The criteria applicability increases when the occupancy area is reduced. However, for common species restricted to a single type of vegetation belt, the use of the IUCN criteria is problematic because of inapplicable and/or misleading thresholds. We adapted the IUCN criteria by modifying the occupancy and occurrence area sizes and by specifying the location. This approach allowed us to establish the first Red List for the bryophyte species in the Canaries, which comprises 105 species (67 mosses and 38 liverworts); among them, 7 are critically endangered, 20 are endangered and 78 are vulnerable. Twenty-six species were classified as near-threatened, 245 were considered to be at low risk and 125 were data deficient (DD). Among the DD ones, 19 corresponded to newly reported species (DD-n) and 40 had no records during the last 30 years (DD-va). Our findings show that the freshwater habitats as well as the habitats in the most restricted cloud forests (with Erica platycodon) contain the majority of the threatened species, followed by other types of laurel forests and high mountain habitats.