Life history traits influence environmental impacts on spatial population synchrony in European birds and butterflies

Nearby populations often experience shared environmental fluctuations and have stronger population synchrony than distant populations. However, different species often show different levels of synchrony across the same areas and environments, possibly because some traits influence their susceptibility to environmental stochasticity. In this paper, we compiled a pan-European collection of long-term annual abundance data on birds and butterflies from eight countries to identify how species' life history traits can influence the effects of environmental synchrony. We show that in birds and butterflies, the impact of environmental synchrony on population synchrony depended on key life history traits. For birds, which had stronger evidence for synchronizing effects of temperature compared to precipitation, the environmental effects on population synchrony depended on generation time, dietary diversity, and migratory tactic. The positive effects of environmental synchrony were stronger in bird species with short generation times (i.e., faster lived), higher dietary diversity, resident species, and short-distance migrants. In butterflies, which had stronger evidence for synchronizing effects of precipitation compared to temperature, we found that environmental effects on population synchrony depended on voltinism, with stronger effects in multivoltine (i.e., faster lived) species. Thus, life history can interact with environmental synchrony in shaping patterns of spatial population synchrony, with implications for predicting impacts of environmental change on species abundances over larger spatial scales. Further understanding of drivers of spatial population synchrony based on long-term abundance data is important in the face of increasingly severe threats to biodiversity and could be key for successful future conservation outcomes.