Scale dependence of temperature as an abiotic driver of species' distributions

Aim Scale dependence of patterns and processes remains one of the major unresolved problems in ecology. The responses of ecosystems to environmental stressors are reported to be strongly scale dependent, but projections of the effects of climate change on species' distributions are still restricted to particular scales and knowledge about scale dependence is lacking. Here we propose that the scale dependence of those species' niche dimensions related to climate change is strongly related to the strength of climatic cross-scale links. More specifically, we hypothesize that the strong cross-scale links between micro-and macroclimatic conditions are related to high cross-scale similarity (low scale dependence) of species' realized temperature niches and, thus, species' spatial distributions. Location This study covers seven orders of magnitude of spatial scale, ranging from local-scale (below a metre) and regional-scale (kilometre) investigations in central European wetland ecosystems to continental-scale (thousands of kilometres) studies of species' distributions. Methods We combined data on the spatial occurrence of species (vegetation records at local and regional scales, digitized distribution maps at the continental scale) with information about the corresponding temperature regime of vascular plant species occurring in environmentally stable wetland ecosystems characterized by strong cross-scale links between micro-and macroclimatic conditions. Results We observed high cross-scale similarity of the characteristics of species temperature niches across seven orders of magnitude of spatial scale. However, the importance of temperature as an abiotic driver decreased nonlinearly with decreasing scale, suggesting greater importance of additional (biotic) drivers of species' occurrence at small spatial scales. Main conclusions We report high cross-scale similarity of realized temperature niches for species inhabiting ecosystems where small-scale environmental noise is low and cross-scale links between micro-and macroclimatic conditions are strong. By highlighting a strong relationship between abiotic and biotic cross-scale similarity, our results will help to improve niche-based species distribution modelling, one of the major assessment tools for determining the ecological effects of climate change.