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

Abstract

Summary 1.Theory predicting that populations with high maximum rates of increase ( r max ) will be less stable, and that metapopulations with high average r max 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 r max obtained using a linear mixed-effects model, ranged from 1·5 to 2·7 per day. Resource levels (captured insect) and midge abundances affected r max . 4. Higher r max was associated with greater temporal variability and lower synchrony as predicted. However, in contrast to expectations, populations with higher r max also had lower mean abundance and were more suppressed by predators. 5. This study demonstrates that the link between r max 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.

Functional traits and environment jointly determine the spatial scaling of population stability in North American birds

“…This might be explained by the high sensitivity (or lower resistance) to environmental variations of “fast” species compared with “slow” ones (Li et al, 2021). In a spatially correlated environment, local populations of “fast” species track environmental fluctuations more closely and thereby exhibit higher spatial synchrony (Trzcinski et al, 2008). Alternatively, the trend in neighborhood synchrony along the fast–slow spectrum may be complicated by time series length in empirical data.…”

The effects of food web structure on ecosystem function exceeds those of precipitation

“…; Hammill et al . ) and other phytotelmata (Kneitel & Miller ; Trzcinski, Walde & Taylor , ). In our study, we found that filter feeder survival (and abundance) decreased virus counts ( r = −0·34, P = 0·002), bacterial densities ( r = −0·40, P = 0·002), algal densities ( r = −0·25, P = 0·02), log ciliate densities ( r = −0·60, P < 0·001) and water turbidity ( r = −0·24, P = 0·03).…”

What determines “suitable habitat” for metapopulation studies? An analysis of environmental gradients and species assemblages in xeric forest openings

“…However, it is only in the multiyear analysis that differences between forests and forest openings become evident. Environmental conditions fluctuate between these two habitat types but in our study were so similar that these differences cannot be detected by one year of data collection (Schooley, 1994; Adler and Drake, 2008; Trzcinski et al, 2008).…”