8 Pages

Complex population dynamics in a host-pathogen-parasitoid interaction

WithS.M. Sait, M. Begon, D.J. Thompson

Theoretical studies that have encompassed multispecies interactions have enhanced our understanding of population and community ecology, but empirical studies of these complex systems are rare. Here, the population dynamics of the Indian meal moth, Plodia interpunctella, and two of its natural enemies, a baculovirus and the solitary endoparasitoid Venturia canescens, are described. Replicated populations consisting of host, host-pathogen, host-parasitoid and host-pathogen-parasitoid combinations were established and the patterns in abundance of each species monitored. The host alone and each of the two-species systems predictably exhibited long term persistence and cyclic fluctuations of approximately one host generation in length. In striking contrast, the three-species populations were characterized by instability and a marked propensity to go extinct. Furthermore, the increase from two to three species resulted in a remarkable shift in period of the host and parasitoid dynamics, which exhibited multigeneration cycles.