Biological control in a disturbed environment
Biological control in a disturbed environment
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受干扰环境中的生物防治
DOI：
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发表时间：
1997
期刊：
影响因子：
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通讯作者：
C. Gilligan
中科院分区：
文献类型：
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作者：
S. Gubbins;C. Gilligan
大多数生态学和流行病学模型描述的是种群之间持续不间断相互作用的系统。然而，许多系统都有生态干扰，例如与季节性作物的种植和收获有关的干扰。在本文中，我们引入宿主-寄生虫-重寄生虫系统作为扰动环境中的生物控制模型，其中宿主-寄生虫相互作用是不连续的。一个模型是一个寄生虫hypeparasite系统，旨在捕捉生物控制的本质，另一个是一个主机寄生虫hypeparasite系统，其中包括更多的功能的人口动态。模型中包括两种类型的不连续性。一个对应于收获时新寄生虫的脉冲，另一个反映了由于种植和收获而导致的宿主的不连续存在。这种不连续性是许多涉及寄生或与一年生宿主的其他相互作用的生态系统的特征。该模型进行了测试，对数据从一个实验调查的持续生物控制的真菌植物寄生虫的生菜小核盘菌的真菌超寄生虫Sporidesmium sclerotivorum，在连续的作物。使用的数学分析，模型拟合和参数估计相结合，有助于观察到的寄生虫的持久性的因素进行检查。分析结果表明，重复种植和收获的主机允许寄生虫坚持保持一定数量的主机组织在系统中的寄生虫可以繁殖。当主机动态不包括明确的模型中，我们表明，均匀混合无法预测的寄生虫种群的持久性，而通过允许异质混合，防止淡出，将空间异质性。包括host 9 s动力学减少异质混合的持久性的影响，虽然预测值的寄生虫种群更接近观察值。持久性的另一种假设，涉及感染率的逐步变化进行了测试和模型拟合显示，在某些环境条件下的变化可能有助于寄生虫的持久性。讨论了相互作用种群模型中扰动和周期强迫的重要性。
Most ecological and epidemiological models describe systems with continuous uninterrupted interactions between populations. Many systems, though, have ecological disturbances, such as those associated with planting and harvesting of a seasonal crop. In this paper, we introduce host—parasite—hyperparasite systems as models of biological control in a disturbed environment, where the host—parasite interactions are discontinuous. One model is a parasite—hyperparasite system designed to capture the essence of biological control and the other is a host—parasite—hyperparasite system that incorporates many more features of the population dynamics. Two types of discontinuity are included in the models. One corresponds to a pulse of new parasites at harvest and the other reflects the discontinuous presence of the host due to planting and harvesting. Such discontinuities are characteristic of many ecosystems involving parasitism or other interactions with an annual host. The models are tested against data from an experiment investigating the persistent biological control of the fungal plant parasite of lettuce Sclerotinia minor by the fungal hyperparasite Sporidesmium sclerotivorum , over successive crops. Using a combination of mathematical analysis, model fitting and parameter estimation, the factors that contribute the observed persistence of the parasite are examined. Analytical results show that repeated planting and harvesting of the host allows the parasite to persist by maintaining a quantity of host tissue in the system on which the parasite can reproduce. When the host dynamics are not included explicitly in the model, we demonstrate that homogeneous mixing fails to predict the persistence of the parasite population, while incorporating spatial heterogeneity by allowing for heterogeneous mixing prevents fade–out. Including the host9s dynamics lessens the effect of heterogeneous mixing on persistence, though the predicted values for the parasite population are closer to the observed values. An alternative hypothesis for persistence involving a stepped change in rates of infection is also tested and model fitting is used to show that changes in some environmental conditions may contribute to parasite persistence. The importance of disturbances and periodic forcing in models for interacting populations is discussed.