Synchrony of Population Fluctuations: The Dominant Influence of Widespread Factors on Local Butterfly Populations

Fluctuations in the abundance of butterflies at many sites in Britain are monitored in a national scheme. Both annual fluctuations and long term trends at individual sites are often very closely synchronised with regional data which excludes the study sites. I argue from such synchrony: (1) that these population are likely to be limited by density-dependent factors and (2) that population fluctuations are little influenced by interactions which are specific to local communities.