Anti-predator defence and the complexity-stability relationship of food webs.
The mechanism for maintaining complex food webs has been a central issue in ecology because theory often predicts that complexity (higher the species richness, more the interactions) destabilizes food webs. Although it has been proposed that prey anti-predator defence may affect the stability of prey-predator dynamics, such studies assumed a limited and relatively simpler variation in the food-web structure. Here, using mathematical models, I report that food-web flexibility arising from prey anti-predator defence enhances community-level stability (community persistence and robustness) in more complex systems and even changes the complexity-stability relationship. The model analysis shows that adaptive predator-specific defence enhances community-level stability under a wide range of food-web complexity levels and topologies, while generalized defence does not. Furthermore, while increasing food-web complexity has minor or negative effects on community-level stability in the absence of defence adaptation, or in the presence of generalized defence, in the presence of predator-specific defence, the connectance-stability relationship may become unimodal. Increasing species richness, in contrast, always lowers community-level stability. The emergence of a positive connectance-stability relationship however necessitates food-web compartmentalization, high defence efficiency and low defence cost, suggesting that it only occurs under a restricted condition.
Kondoh
Michio
M
Centre for Ecological Research, Kyoto University, Hirano 2-509-3, Otsu, Japan. mkondoh@rins.ryukoku.ac.jp
D000818:Animals; D003198:Computer Simulation; D004463:Ecology; D004924:Escape Reaction / Q000502:physiology*; D020387:Food Chain; D008962:Models, Theoretical; D011157:Population Dynamics; D011235:Predatory Behavior / Q000502:physiology