Highly Variable Spread Rates in Replicated Biological Invasions: Fundamental Limits to Predictability
Brett A. Melbourne1,* and
Alan Hastings2
Although mean rates of spread for invasive species have been
intensively studied, variance in spread rates has been neglected.
Variance in spread rates can be driven exogenously by environmental
variability or endogenously by demographic or genetic stochasticity
in reproduction, survival, and dispersal. Endogenous variability
is likely to be important in spread but has not been studied
empirically. We show that endogenously generated variance in
spread rates is remarkably high between replicated invasions
of the flour beetle
Tribolium castaneum in laboratory microcosms.
The observed variation between replicate invasions cannot be
explained by demographic stochasticity alone, which indicates
inherent limitations to predictability in even the simplest
ecological settings.
2 Department of Environmental Science and Policy, University of California, Davis, CA 95616, USA.
* To whom correspondence should be addressed. E-mail: brett.melbourne{at}colorado.edu
