On the Inadequacy of Simple Models of Mutual Interference for Parasitism and Predation

Abstract

The widely used Hassell-Varley model of mutual interference between arthropod parasites is interpreted in terms of more fundamental behavioral models. It is over-simplified in neglecting the dependence of mutual interference on parasite density. The behavioral models suggest that mutual interference in the field is much less important than had been supposed. Non-random search for a patchily distributed host can lead to an apparent interference effect (pseudo-interference), even in the absence of the time-wasting interactions on which the behavioral models are based. Conventional laboratory experiments are a poor guide to interference in the field. They are usually conducted at high parasite densities and over-estimate the importance of mutual interference. Furthermore, as spatial heterogeneity is rarely considered, they under-estimate the effects of pseudo-interference. The applicability of these ideas to predation rather than parasitism is discussed.