In host–parasitoid interactions, parasitism risk experienced by each host may decrease as the host density increases (referred to as the dilution effect) when parasitoids can parasitize a limited number of hosts at a given time no matter how abundant hosts are. In the relationship between parasitism risk and host–parasitoid dynamics, the dilution effect is generally considered as a destabilizing factor, whereas variability in parasitism risk among hosts is regarded a stabilizing factor. However, although the dilution effect and variability in parasitism risk have been studied in isolation, the simultaneous expression of these two factors in host–parasitoid systems has not been investigated. This study examines the dilution effect in a patchy environment using a simulation model, with a specific focus on the $C{V}^2>1$ rule (which states that $C{V}^2>1$ is a condition for stability where $CV$ is the coefficient of variation in parasitism risk among hosts). The simulation model shows that the $C{V}^2>1$ rule is a good predictor of stability of the model regardless of the presence or absence of the dilution effect. It was also found that the dilution effect increases $C{V}^2$ and stabilizes the host–parasitoid dynamics.

在寄主与拟寄生物的相互作用中，无论寄主数量有多大，在给定的时间寄生物都能寄生有限数量的寄主，随着寄主密度的增加，每个寄主遭受的寄生虫风险可能会降低。在寄生虫风险与宿主-寄生虫动态之间的关系中，稀释效应通常被认为是破坏因素，而宿主之间寄生虫风险的变化被认为是稳定因素。然而，尽管已经单独研究了寄生效应风险中的稀释效应和变异性，但尚未研究这两个因素在宿主-寄生虫系统中的同时表达。这项研究使用模拟模型研究了在零散环境中的稀释效应，特别关注了 $C{V}^2>\mathrm{1个}$ 规则（其中指出 $C{V}^2>\mathrm{1个}$ 是稳定的条件 $CV$是宿主中寄生虫风险的变异系数）。仿真模型表明 $C{V}^2>\mathrm{1个}$规则是模型稳定性的良好预测指标，而与是否存在稀释效果无关。还发现稀释效果增加 $C{V}^2$ 并稳定了宿主-寄生虫的动力学。