Large-scale climate synchronizes the timing of flowering by multiple species

Spatially synchronous dynamics are widespread in ecology, but attributing them to environmental correlation, as originally proposed by Moran, is complicated by the synchronizing influences of dispersal and trophic interactions. Nonetheless, spatially correlated masting in trees and its relation to spatial covariation in weather patterns over large regions are strongly suggestive of coupling of populations by large-scale climate. I investigated the potential for population synchronization by large-scale climate in an analysis of long-term (i.e., 50-yr) dynamics of the timing of flowering by three species of plants in 26 populations spanning several hundred kilometers in Norway. Temporal fluctuations in the timing of flowering were highly correlated across populations, both within and among species. Moreover, large-scale climatic fluctuation (the Arctic Oscillation) synchronized the timing of flowering across all three species over distances up to 500 km. These results represent a clear demonstration of population linkage by large-scale climate, and suggest that populations of multiple species may be influenced simultaneously over broad distances by climatic change.