Diversity Of Liverworts And Hornworts In Polylepis Sericea Forests In The Andes Of Venezuela

The Polylepis forests of the high Andes host a unique biodiversity of plants and animals, yet are widely being destroyed by fire and cattle grazing and are considered as one of the most threatened ecosystems of South America. We inventoried liverwort and hornwort diversity in seven Polylepis sericea stands in the Andes of Venezuela (Sierra Nevada National Park) between 3400 and 4150 m. Hornworts were very few but liverworts were plentiful. Most of the species occurred on non-tree substrates (soil, rock, rotten wood), and less than one third were epiphytes. The relatively low number of epiphytic species and the prevalence of the smooth mat life form were indicative of relatively dry climatic conditions in the investigated forests. The strongly exfoliating bark of P sericea may also have inhibited the epiphytic diversity. High species turnover between the two main study sites (Loma Redonda station, Sierra de Santo Domingo) probably reflected a 500 m elevational difference between the sites. Many species reached highest elevational occurrence in the forests and seven species were new to Venezuela (Anthoceros tristanianus, Kurzia brasiliensis, Lophocolea tenerrima, Metzgeria agnewiae, M jamesonii, Plagiochila cleefii, Riccardia wallisii). The new name Frullania intumescens var. closterantha (Spruce) Gradst. & Pocs comb. nov. is proposed. Almost half of the liverwort species had predominantly Andean ranges and seven species were largely restricted to the northern Andes. The elevated number of liverwort species with restricted ranges underscores the significance of Polylepis forests as a habitat for liverworts and their importance for conservation. The important role of saxicolous, lignicolous and terrestrial species in shaping liverwort and hornwort diversity in the Venezuelan Polylepis forests indicates that non-epiphytic taxa should not be neglected in studies on liverwort and hornwort diversity of these forests.