Evolution of density-dependent handling times in a predator-prey model

Beskrivning

The competitive exclusion principle states that in a constant population two species competing for the same limited resource cannot coexist. This cannot be generalised to non-constant populations. In particular, it has been shown that two predator species competing for the same niche can coexist if the population exhibits non-equilibrium dynamics such as limit cycles. In addition to the ecological question, there emerges the problem whether the coexistence of different predator types competing for a single prey is evolutionarily robust and attainable. Geritz et al. used the theory of adaptive dynamics to study the evolution of the handling time in a model with Holling type II functional response. They found that under certain conditions the handling time undergoes evolutionary branching and leads to the establishment of the evolutionarily robust coexistence of two predator types. Essential is the assumption of a trade-off between the handling time and the conversion factor connecting the predator's birth rate to its capture rate. It was found that the predator type with the short handling time dominates in the part of the population cycle where the prey is abundant, while the other type prevails when the prey is rare. Ecologically this makes sense: when the prey density is low, prospects of capturing new prey are diminished and it becomes worthwhile to cling to the prey one has already got despite of its gradually decreasing returns. When the prey is common, however, it is easy to replace the partially spent prey by a new one. In this presentation we derive a Holling type II functional response with handling time that depends on the prey density. The ecological setting raises some considerations on the importance of the mechanistic approach when we look at the functions which model the population dynamics as well as leads to new interesting evolutionary questions. Using the theory of adaptive dynamics, we investigate if at least some level of density dependence is favoured whether or not the population is cycling. A further question is if the density dependence can eliminate the possibility of coexistence of different predator types. This makes sense when a single predator with density dependent handling time dynamically shifts its niche between low and high prey densities depending on the phase of the population cycle in a way that a predator with a fixed handling time cannot.

Period	17 aug 2020 → 20 aug 2020
Händelsetitel	eSMB
Typ av evenemang	Konferens
Omfattning	Internationell