Experimental studies on acarine predator–prey interactions: the distribution of search effort and the functional and numerical responses of predators in a patchy environment (Acarina: Phytoseiidae)

Abstract

Laboratory experiments revealed that Phytoseiulus persimilis distributed its search effort in relation to prey density in a patchy environment, whereas Amblyseius degenerans distributed its search effort randomly among patches of prey. The main factor responsible for the aggregative response of P. persimilis was the length of its first visit to the patches. Although the functional responses of both predators changed with time, only those of P. persimilis closely reflected changes occurring in its distribution of search effort. The spatial complexity of the environment did not affect the overall predation rates of P. persimilis but it reduced its reproductive output. However, the predation rates of A. degenerans were adversely affected, suggesting that its fecundity would also be reduced in a spatially complex environment. Phytoseiulus persimilis distributed its progeny among patches containing relatively high prey densities and avoided ovipositing in the patch containing fewest prey. Neither species foraged optimally and possible reasons for this are discussed.