Spatial variation in population growth rate and community structure affects local and regional dynamics.

Summary 1 Theory predicting that populations with high maximum rates of increase (rmax) will be less stable, and that metapopulations with high average rmax will be less synchronous, was tested using a small protist, Bodo, that inhabits pitcher plant leaves (Sarracenia purpurea L.). The effects of predators and resources on these relationships were also determined. 2 Abundance data collected for a total of 60 populations of Bodo, over a period of 3 months, at six sites in three bogs in eastern Canada, were used to test these predictions. Mosquitoes were manipulated in half the leaves partway through the season to increase the range of predation rates. 3 Dynamics differed greatly among leaves and sites, but most populations exhibited one or more episodes of rapid increase followed by a population crash. Estimates of rmax obtained using a linear mixed-effects model, ranged from 1·5 to 2·7 per day. Resource levels (captured insect) and midge abundances affected rmax. 4 Higher rmax was associated with greater temporal variability and lower synchrony as predicted. However, in contrast to expectations, populations with higher rmax also had lower mean abundance and were more suppressed by predators. 5 This study demonstrates that the link between rmax and temporal variability is key to understanding the dynamics of populations that spend little time near equilibrium, and to predicting and interpreting the effects of community structure on the dynamics of such populations.