ESA/SER Joint Meeting (August 5 -- August 10, 2007)

COS 16-2 - The effects of endogenous ecological memory on population resilience in a variable environment

Monday, August 6, 2007: 1:50 PM
Santa Clara I, San Jose Hilton
Michael Golinski, Mathematics and Statistics and Environmental Biology, University of Guelph, Guelph, ON, Canada, Chris Bauch, Mathematics and Statistics/Ecology and Evolutionary Biology, University of Guelph and Princeton University, Guelph, ON, Canada and Madhur Anand, Global Ecological Change & Sustainability Laboratory, School of Environmental Sciences, University of Guelph, Guelph, ON, Canada

Endogenous ecological memory (EEM) refers to the phenomenon where past states of a system (i.e. population density) can influence present states.  Dormancy is an example of EEM.  In this paper, we address the effects of EEM on qualitative changes in population dynamics over-time.  The goal was to determine the effects of EEM on the resilience of a population.  We analyze the discrete-time Ricker model St+1 = RStexp(r(1-St/K)) with environmental stochasticity.  We explore the model when time-delays are restricted to the density-dependent (exp(r(1-St/K))) component of the model and log-normal multiplicative noise is incorporated as well.  Simulation results show that population resilience, as measured by the standard deviation of population density about the carrying capacity, decreases as the duration of EEM increases.  Moreover, resilience decreases with increasing fecundity R, which differs from the predictions of some other theoretical and empirical work.  We observe boom-bust cycles in population density for significantly long time-delays in density dependence.  These cycles become more extreme as the regulating effects of density-dependence are increasingly delayed.