Evolution of handling time can destroy the coexistence of cycling predators


  • Present address: Shengqiang Liu, Department of Mathematics, Xiamen University, Xiamen, 361005, China.
    e-mail: lsqmath@yahoo.com.cn

Éva Kisdi, Rolf Nevanlinna Institute, Department of Mathematics and Statistics, FIN-00014 University of Helsinki, Finland.
Tel.: +358 9 1915 1489; fax: +358 9 1915 1400;
e-mail: eva.kisdi@helsinki.fi


Several consumers (predators) with Holling type II functional response may robustly coexist even if they utilize the same resource (prey), provided that the population exhibits nonequilibrium dynamics and the handling time of predators is sufficiently different. We investigate the evolution of handling time and, in particular, its effect on coexistence. Longer handling time is costly in terms of lost foraging time, but allows more nutrients to be extracted from a captured prey individual. Assuming a hyperbolically saturating relationship between handling time and the number of new predators produced per prey consumed, we obtain three results: (i) There is a globally evolutionarily stable handling time; (ii) At most two predator strategies can coexist in this model; (iii) When two predators coexist, a mutant with intermediate handling time can always invade. This implies that there is no evolutionarily stable coexistence, and the evolution of handling time eventually leads to a single evolutionarily stable predator. These results are proven analytically and are valid for arbitrary (not only small) mutations; they however depend on the relationship between handling time and offspring production and on the assumption that predators differ only in their prey handling strategy.