Critical predictors of functional, phylogenetic, and taxonomic diversity are geographically structured in lichen epiphytic communities

Abstract

Assessing the response of biological communities to contrasting environmentalconditions is crucial to predict the effects of global change drivers. The influenceof multiple environmental factors may differ depending on the diversity facetconsidered, which emphasizes the need to simultaneously evaluate the functional(FD), phylogenetic (PD) and taxonomic (TD) diversity.2. To examine how these facets of biodiversity respond to environmental changes,we studied lichen epiphytic communities across 47 beech forest fragments fromtwo biogeographic regions. We applied structural equation modelling to relatehabitat fragmentation, climate and habitat quality with FD, PD and TD. We com‐pared the community response to contrasting climatic conditions by analysing in‐dependently Atlantic and Mediterranean communities.3. We found different major drivers of biodiversity patterns across biogeographicregions. Habitat fragmentation performed the highest effect on lichen communi‐ties, with a reduction of FD, PD and TD at both regions. However, the influenceof climate was stronger in the Atlantic region than in the Mediterranean region,where the effect of habitat quality was superior. The effect of the environmentalpredictors over PD and TD was both direct and indirect through the differentcomponents of FD, and their intensity and sign differed across regions. Changesin PD were not related to changes in TD.4. Synthesis. Our results evidenced that the major environmental drivers affect‐ing epiphytic communities were geographically structured. These drivers modi‐fied the diversity of the epiphytic community directly but also indirectly throughchanges in FD, which emerged as a causal but not unique determinant of PD andTD. Our findings also showed the difficulty for inferring TD through PD. Theseresults emphasize the essential role of FD predicting part of the response of lichencommunities to global change drivers but also highlight the importance of con‐sidering multiple biodiversity facets to understand the effects of environmentalchange on community structure.