School of Aquatic and Fishery Sciences, The University of Washington, 1122 NE Boat St, Box 355020, Seattle,WA98195,USA.
Department of Biology, University of San Diego, 5998 Alcala Park, San Diego, CA 92110, USA.
Viruses. 2020 Jan 25;12(2):141. doi: 10.3390/v12020141.
The use of viral pathogens to control thepopulation size of pest insects has produced both successful and unsuccessful outcomes. Here, we investigate whether those biocontrol successes and failures can be explained by key ecological and evolutionary processes between hosts and pathogens. Specifically, we examine how heterogeneity inpathogen transmission, ecological and evolutionary tradeoffs, andpathogen diversity affect insect population density and thus successful control. Wefirst review theexisting literature and then use numerical simulations of mathematical models to further explore these processes. Our results show that thecontrol of insect densities using viruses depends strongly on theheterogeneity of virus transmission among insects. Overall, increased heterogeneity of transmission reduces theeffect of viruses on insect densities and increases thelong-term stability of insect populations. Lower equilibrium insect densities occur when transmission is heritable and when there is atradeoff between mean transmission and insect fecundity compared to when theheterogeneity of transmission arises from non-genetic sources. Thus, theheterogeneity of transmission is akey parameter that regulates thelong-term population dynamics of insects and their pathogens. Wealso show that both heterogeneity of transmission and life-history tradeoffs modulate characteristics of population dynamics such as thefrequency and intensity of ``boom--bust" population cycles. Furthermore, we show that because of life-history tradeoffs affecting thetransmission rate, theuse of multiple pathogen strains is more effective than theuse of asingle strain to control insect densities only when thepathogen strains differ considerably intheir transmission characteristics. By quantifying theeffects of ecology and evolution on population densities, we are able to offer recommendations to assess thelong-term effects of classical biocontrol.
利用病毒病原体来控制害虫的种群数量已经产生了成功和不成功的结果。在这里，我们研究了这些生物防治的成功和失败是否可以用宿主和病原体之间的关键生态和进化过程来解释。具体来说，我们检查了病原体传播的异质性、生态和进化权衡以及病原体多样性如何影响昆虫种群密度，从而影响控制效果。我们首先回顾了现有文献，然后使用数学模型的数值模拟来进一步探讨这些过程。我们的结果表明，利用病毒控制昆虫密度强烈依赖于昆虫之间病毒传播的异质性。总的来说，传播的异质性增加会降低病毒对昆虫密度的影响，并增加昆虫种群的长期稳定性。当遗传因素影响病毒传播时，或者当平均传播与昆虫繁殖力之间存在权衡时，昆虫的平衡密度会降低，与传播异质性来自非遗传因素的情况相比。因此，传播的异质性是调节昆虫及其病原体长期种群动态的关键参数。我们还表明，传播的异质性和生活史权衡都会调节种群动态的特征，如“繁荣-萧条”种群周期的频率和强度。此外，我们还表明，由于影响传播率的生活史权衡，只有当病原体菌株在传播特征上有很大差异时，使用多种病原体菌株来控制昆虫密度才比使用单一菌株更有效。通过量化生态和进化对种群密度的影响，我们能够提供评估经典生物防治的长期效果的建议。
