Geographic patterns in functional diversity deficits are linked to glacial-interglacial climate stability and accessibility

AimLate Quaternary climate change can be an important determinant of large-scale species richness patterns, but it is currently unknown if its effects also extend to functional diversity (FD) and thus potentially ecosystem functioning. This study assessed whether deficits in contemporary FD, relative to expectations based on contemporary environmental regions and species richness, were associated with glacial-interglacial climate stability and accessibility from glacial refugia. LocationEurope MethodsAtlas data on distributions of plant species and functional trait information were used to estimate functional richness (F-Rich) and dispersion (F-Disp) for approximate to 50x50km grid cells across Europe. Maximum expected FD was calculated using both quantile regression and a null-model approach, with species richness and contemporary environmental regions as constraints. Then, the proportion of the potential FD present in a grid cell - the realized-to-potential FD ratio (R/P) - was estimated. Spatial autoregressive modeling with information-theoretic multi-model selection were used to estimate the explanatory importance and predictive ability of glacial-interglacial climate instability and accessibility to recolonization from glacial refugia for R/P ratios. ResultsMinimum and median R/P ratios were 58% and 74% for F-Rich and 82% and 93% for F-Disp, showing that realized FD is often lower than expectations from species richness and contemporary environmental regions. FD deficits were significantly associated with glacial-interglacial Quaternary climate change (F-Rich-R-2: 0.52; F-Disp-R-2: 0.41), even after accounting for contemporary climate. F-Rich and F-Disp R/P ratios were the highest in areas with low climatic instability and close to the major glacial temperate refuge regions. Main ConclusionsRealized macro-scale FD patterns appear to be in moderate disequilibrium with contemporary richness and environmental regions. Importantly, small R/P ratios are significantly associated with both historical and contemporary climate. These findings suggest that future climate change may elicit long-term functional disequilibria and thus also have long-term consequences for ecosystem functioning.