Stability and Instability incurred by Aggregation in Host-Parasitoid Systems

Aggregation by predator and parasitoid is common in nature. In this paper, the role of aggregation in host-parasitoid system is investigated using two discrete-time host-parasitoid models. The aggregation is incorporated through introducing negative binomial distribution into the encounter probability. Numerical analyzes show that the host-parasitoid dynamics may be stabilized when the aggregation is moderate. However, we also find that the host-parasitoid dynamics may be destabilized or the parasitoid population may be driven to extinction by strong aggregation of parasitism. Although not strictly consistent with the previous notion, aggregation stabilizing host-parasitoid dynamics, the findings in this study is still interesting and can enlighten us in some ecological applications.