Patterns of European Ant Communities Reveal a Functionally Coherent Holarctic Fauna

Abstract

Here we examine the extent to which European patterns of ant diversity and functional composition conform with those documented in North America. Following protocols previously used in North America, ant species distribution and behavioural dominance were quantified at fifteen sites on two environmental gradients, one following elevation (140–1830 m) in France and the other tree cover (0–95%) in Denmark. Pitfall traps were used to assess species distributions, and behaviour at tuna baits was used to inform behavioural dominance. We specifically test three predictions based on North American patterns: (1) Species richness and overall levels of behavioural dominance will decline with increasing thermal stress. (2) Geographic patterns of key taxa in Europe will be consistent with those in North America. (3) Behavioural dominance of European taxa will be consistent with related taxa in North America. We then use our results to classify the European ant fauna into functional groups, as had been done for North American ants. Based on these functional groups, we analyse distributional patterns along our gradients and re-analyse ant community data from published studies to provide a more comprehensive understanding of the structure of European ant communities. Distributional and behavioural predictions of the European ant taxa were consistent with those in North America. Geographical patterns of functional-group composition were very similar to those previously recorded for North America, varying systematically and predictably along the environmental gradients. Our findings indicate that there is a functionally coherent ant fauna throughout the Holarctic.