Low spatial congruence between temporal functional β‐diversity and temporal taxonomic and phylogenetic β‐diversity in British avifauna

Assessing spatial and temporal patterns of biodiversity change is essential to understand how communities vary over time and confront to environmental changes for the resilience of ecosystem functioning. We use data from two bird atlases of Britain collected during the breeding periods 1988–1991 and 2008–2011 to measure temporal β‐diversity of taxonomic, functional and phylogenetic dimensions and examine the relationship and the level of congruence of the three dimensions of temporal β‐diversity and their respective partitioned components (turnover‐nestedness). Temporal β‐diversity, turnover and nestedness patterns were highly congruent for the taxonomic and phylogenetic dimension, although these dimensions were weakly associated with the functional dimension. We found higher levels of temporal changes for the taxonomic (mean Jaccard β‐diversity 0.27) and phylogenetic (mean Jaccard β‐diversity 0.21) dimensions than for the functional dimension (mean Jaccard β‐diversity 0.09), implying that despite the changes in species composition the functional composition of the communities remained less affected. For taxonomic and phylogenetic dimensions, turnover contributed more than nestedness to shaping β‐diversity, while for functional β‐diversity the two components contributed similarly. Communities at higher altitudes were also more functionally similar in 20 years but with more changes in taxonomic and phylogenetic diversity possibly due to environmental filtering. We hypothesize that the low congruence might be due to species with extreme trait values persisting throughout time and retaining the volume of functional space and thus contributing to the low temporal change of functional diversity despite the high levels of change in species composition, perhaps an indication of functional “stability.”