Isolation affects tree‐scale epiphytic lichen community structure on New Zealand mountain beech trees

Question: Is epiphytic lichen community structure significantly affected by isolation from source community? Location: Foothills of the Southern Alps, South Island, New Zealand. Methods: Epiphytic lichen richness and environmental variables were measured on 382, young Nothofagus solandri var. cliffortioides (Hook. f.) Poole (mountain beech) trees that had recently colonized grassland adjacent to a forest remnant. Richness and the presence of individual lichen taxa were modelled as a function of isolation from the forest fragment, tree size and other habitat conditions. Results: Richness of epiphytic lichen communities was negatively related to tree isolation, although this effect was much smaller than the effects of tree size and other local (tree‐scale) habitat conditions. Different lichen taxa responded in different ways to isolation, area effects and local habitat conditions. Conclusions: This study shows that many epiphytic lichens on mountain beech are limited in their ability to colonize new substrate, even over distances of less than 1 km, which may be due to limitation in dispersal and/or establishment. Lichens are greatly influenced by local habitat conditions, such as tree size, and in this particular environment their negative interaction with sooty moulds is an important driver of community structure.