Identification of outbreak classes

Population-level consequences of antipredator behavior: a metaphysiological model based on the functional ecology of the leaf-eared mouse

We present a predator-prey metaphysiological model, based on the available behavioral and physiological information of the sigmodontine rodent Phyllotis darwini. The model is focused on the population-level consequences of the antipredator behavior, performed by the rodent population, which is assumed to be an inducible response of predation avoidance. The decrease in vulnerability is explicitly considered to have two associated costs: a decreasing foraging success and an increasing metabolic loss. The model analysis was carried out on a reduced form of the system by means of numerical and analytical tools. We evaluated the stability properties of equilibrium points in the phase plane, and carried out bifurcation analyses of rodent equilibrium density under varying conditions of three relevant parameters. The bifurcation parameters chosen represent predator avoidance effectiveness (A), foraging cost of antipredator behavior (C(1)'), and activity-metabolism cost (C(4)'). Our analysis suggests that the trade-offs involved in antipredator behavior plays a fundamental role in the stability properties of the system. Under conditions of high foraging cost, stability decreases as antipredator effectiveness increases. Under the complementary scenario (not considering the highest foraging costs), the equilibria are either stable when both costs are low, or unstable when both costs are higher, independent of antipredator effectiveness. No evidence of stabilizing effects of antipredator behavior was found.

Biotic disturbance agents in the boreal forest: considerations for vegetation change models

Disturbance regimes strongly determine vegetation patterns and succession in the boreal landscape. One of the current challenges for boreal vegetation modellers is to represent disturbance agents as dynamic factors that can respond to climate change. Outbreak species of insects and plant pathogens can cause marked changes in vegetation patterns and should be incorporated into vegetation change models. This introduction to the ecology of boreal biotic disturbance agents is designed as a brief overview for global change researchers and modellers. We discuss the importance of biotic disturbance agents in the boreal forest, offer an overview of their ecology, and review modelling approaches. We illustrate these issues with examples from different systems, drawing largely from our experience with bark beetles.