Taxon- compared with trait-based analysis of epiphytes, and the role of tree species and tree age in community composition

Background: Trait-based assembly rules are a powerful tool in community ecology, used to explore the pattern and process of community structure (richness and composition). Aims: A preliminary test for the utility of trait-based assembly rules in explaining cryptogamic epiphyte communities (lichens and bryophytes). Methods: We sampled epiphytes from three different tree species (aspen, birch and pine), and from trees of contrasting age. The community composition of epiphyte species (taxon analysis) and functional groups (trait analysis) was summarised using multivariate ordination (nonmetric multidimensional scaling, NMDS). Results: Ordination documented a widely observed pattern in which different tree species have taxonomically different epiphyte communities. However, NMDS sample scores were correlated to tree age in the trait-based analysis, but not in the taxon analysis. Conclusions: Our results point to the existence of a common pattern in community traits during succession (on trees of different age) when measured for epiphyte communities with contrasting taxonomic composition. This pattern is evidenced by consistent trends in lichen growth form and reproductive strategy (sexual vs. asexual).