The spatial scale of time-lagged population synchrony increases with species dispersal distance.

Aim Time-lagged population synchrony, where spatially separated populations show similar fluctuations in abundance lagged over time, is thought to be driven by dispersal among populations. When dispersal is proportional to population density or positively density dependent, and individuals move readily from population A to population B, then as population A increases, the increased number of dispersers from population A to B will cause a subsequent increase in population B. If true, then time-lagged synchrony should be strongest at a species' typical dispersal distance, because the rate of exchange between populations will be greatest at that distance. Location United Kingdom (U. K.). Time period 1994 - 2013. Major taxa studied Birds (class Aves). Methods We estimated the spatial scale of 1-year-lagged population synchrony for 76 U.K. bird species, using 20 years of bird count data collected at 2,415 locations by the British Breeding Bird Survey. We then compared these spatial scales with published mean natal and breeding dispersal distance estimates (ranging from 0.1 to 25.8 km) for the same species based on an independent, large-scale, mark-recapture dataset of 492,272 bird recaptures in Britain and Ireland. Results We found strong, positive cross-species relationships between the spatial scale of time-lagged synchrony and mean natal and breeding dispersal distance estimates from the mark-recapture study. However, average spatial scales of time-lagged synchrony were more than 60 km longer than those from mark-recapture data, with scales ranging from 5 to 185 km. Main conclusions Ours is the first study to show that the spatial scale of time-lagged synchrony increases with species dispersal distance. The scale of synchrony was larger than expected, probably because mark-recapture data underestimated the real dispersal distances, or because dispersal synchronizes populations at a larger spatial scale than that of dispersal (e.g., through formation of travelling waves), or both. Nevertheless, the strong relative concordance is consistent with the explanation that time-lagged synchrony results from dispersal among populations. [ABSTRACT FROM AUTHOR]