Effect of rock climbing on the calcicolous lichen community of limestone cliffs in the northern Swiss Jura Mountains

Exposed limestone cliffs in the Swiss Jura Mountains harbour a diverse lichen community with some rare species. Sport climbing has recently increased in popularity on these cliffs. We examined the effect of sport climbing on calcicolous lichens by assessing species diversity and cover of lichens in climbed and unclimbed areas of 10 isolated cliffs in the northern Swiss Jura Mountains. We also investigated possible associations between lichens and lichen-feeding land snails on these cliffs. A total of 38 calcicolous lichen species, three bryophytes and one alga were found on the rock faces of 10 cliffs. Twenty lichen species (52.6%) were epilithic, 16(42.1%) endolithic and two (5.3%) foliose. Overall, the epilithic lichen species covered 8.3% of the rock surface, endolithic species 10.2%, and foliose species 0.03%. Climbed and unclimbed rock areas did not differ in total number of lichen species, species density (number of species per 100 cm(2)) or total lichen cover. However, the frequency of occurrence of epilithic lichens was lower along climbing routes than in unclimbed areas. A multi-response permutation test showed that the lichen community composition of climbed areas differed from that of unclimbed areas. The dissimilarity of lichen communities between climbed and unclimbed areas increased with increasing climbing intensity on the focal route in climbed areas, but not with the age of the climbing route. Five of the 11 snail species recorded on the cliff faces were specialized lichen feeders. Plots along climbing routes harboured fewer snail species than plots in unclimbed areas. Total snail abundance was positively correlated with lichen species richness, but no correlation between snail species richness and lichen species richness was found. Our results indicate that frequent rock climbing can change the lichen community and reduce the snail community of limestone cliffs. A climbing-related reduction of snail abundance may also alter the lichen-herbivore interaction and indirectly change competitive interactions among lichen species.