Population dynamics of pampas mice (Akodon azarae): signatures of competition and predation exposed through time-series modeling

KITTLEIN, MARCELO J.

Population Ecology

Springer

Lugar: Hamburgo; Año: 2009 vol. 51 p. 143 - 151

1438-3896

The ability of four mechanistic population models to mirror a five-year time series of seasonal densities of pampas mice, Akodon azarae, from central Argentina, is evaluated in this paper. The different models included, singly or in combination, the effects of a putative competitor and a specialist predator on the dynamics of pampas mice. The most simple model, a logistic single species stochastic differential equation, failed to fit the observed time series satisfactorily (R2model = 0.36); while models including interspecific effects gave much better fits with increasing model complexity (Competition R2model = 0.71, Predation R2model = 0.62, Competition and Predation R2model = 0.83). Using Akaike’s information criterion the Competition model is selected as the best alternative in regard to model fit and model complexity. Synthetic time series probes obtained by simulations from the parameterized stochastic mechanistic models are significantly different, and signal the Competition plus Predation model as a slightly better alternative than the Competition model. The differences between both methods for selecting models signals that the incorporation of predation improves only slightly the match between the predicted and observed time-series and that these slight improvement is not sufficient to override the increase in model complexity. Competition thus seems to play a more important role than predation in shaping the population dynamics of pampas mice.