半离散寄主-寄生蜂种群动力学模型中的全局再分配和局部迁移
Global redistribution and local migration in semi-discrete host-parasitoid population dynamic models
摘要：
寄主-寄生蜂种群动力学经常使用半离散/混合建模框架进行探测。在这里，在离散时间模型中的更新函数连接每年的人口密度的变化是通过求解常微分方程，机械地描述主机变得容易受到寄生虫攻击时的相互作用。我们使用这种半离散的形式主义，研究两个关键的空间效应：在脆弱时期的补丁之间的寄生虫的本地移动（迁移）;和每年的种群分布在补丁以外的脆弱时期。我们的研究结果表明，在没有任何再分配，恒定的密度无关的迁移和寄生蜂攻击率是无法稳定，否则不稳定的主机寄生种群动力学。有趣的是，包括主机重新分配（但不是寄生虫重新分配）开始之前的脆弱期，可以导致两个物种的稳定共存。接下来，我们考虑III型功能反应（寄生虫攻击率随宿主密度增加），其中没有任何空间效应导致中性稳定的宿主-寄生虫平衡。和以前一样，密度无关的寄生蜂迁移本身再次不足以稳定的种群动力学和主机重新分配提供了一个稳定的影响。最后，我们表明，III型功能反应结合密度依赖性寄生虫迁移导致稳定共存，即使在没有人口再分配。总之，我们已经系统地表征参数制度导致稳定/不稳定的种群动力学与不同形式的空间异质性耦合到寄生虫的功能响应，使用机械制定的半离散模型。
英文摘要：
Host-parasitoid population dynamics is often probed using a semi-discrete/hybrid modeling framework. Here, the update functions in the discrete-time model connecting year-to-year changes in the population densities are obtained by solving ordinary differential equations that mechanistically describe interactions when hosts become vulnerable to parasitoid attacks. We use this semi-discrete formalism to study two key spatial effects: local movement (migration) of parasitoids between patches during the vulnerable period; and yearly redistribution of populations across patches outside the vulnerable period. Our results show that in the absence of any redistribution, constant density-independent migration and parasitoid attack rates are unable to stabilize an otherwise unstable host-parasitoid population dynamics. Interestingly, inclusion of host redistribution (but not parasitoid redistribution) before the start of the vulnerable period can lead to stable coexistence of both species. Next, we consider a Type-III functional response (parasitoid attack rate increases with host density), where the absence of any spatial effects leads to a neutrally stable host-parasitoid equilibrium. As before, density-independent parasitoid migration by itself is again insufficient to stabilize the population dynamics and host redistribution provides a stabilizing influence. Finally, we show that a Type-III functional response combined with density-dependent parasitoid migration leads to stable coexistence, even in the absence of population redistributions. In summary, we have systematically characterized parameter regimes leading to stable/unstable population dynamics with different forms of spatial heterogeneity coupled to the parasitoid's functional response using mechanistically formulated semi-discrete models.
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