Predator mediated coexistence in zooplankton: the importance of behavioural mechanisms

摘要

A predator can promote prey coexistence numerically, by reducing the abundance of competing prey via consumption, or behaviourally, by modifying the behaviour of prey so as to reduce the intensity of interspecific competition (Kotler & Holt 1989). Early theoretical work on consumer-resource dynamics has shown that numerically mediated coexistence is unrealistic without selective feeding by the predator (Chase et al. 2002). Two forms of selective feeding have proved promising, i) preferential feeding on the dominant competitor and ii) switching preference for the most common prey. Preferential feeding ensures that the dominant competitor (i.e. the species that tolerates lower food levels) is limited primarily by the predator and the inferior competitor by the resource. This form of selective feeding might be expected whenever the competitive dominant is also more vulnerable to predator attacks, as often observed among co-occurring zooplanktonic prey (e.g. Lapesa et al. 2002). The negative relationship between competitive ability and resistance to predators is likely to evolve among prey species due to the allocation trade-off between defense and maintenance.