Naranjo Steven E, Ellsworth Peter C
USDA-ARS, Arid-Land Agricultural Research Center;
Department of Entomology, Maricopa Agricultural Center, University of Arizona.
J Vis Exp. 2017 Nov 1(129):56150. doi: 10.3791/56150.
Life tables provide a means of measuring the schedules of birth and death from populations over time. They also can be used to quantify the sources and rates of mortality in populations, which has a variety of applications in ecology, including agricultural ecosystems. Horizontal, or cohort-based, life tables provide for the most direct and accurate method of quantifying vital population rates because they follow a group of individuals in a population from birth to death. Here, protocols are presented for conducting and analyzing cohort-based life tables in the field that takes advantage of the sessile nature of the immature life stages of a global insect pest, Bemisia tabaci. Individual insects are located on the underside of cotton leaves and are marked by drawing a small circle around the insect with a non-toxic pen. This insect can then be observed repeatedly over time with the aid of hand lenses to measure development from one stage to the next and to identify stage-specific causes of death associated with natural and introduced mortality forces. Analyses explain how to correctly measure multiple mortality forces that act contemporaneously within each stage and how to use such data to provide meaningful population dynamic metrics. The method does not directly account for adult survival and reproduction, which limits inference to dynamics of immature stages. An example is presented that focused on measuring the impact of bottom-up (plant quality) and top-down (natural enemies) effects on the mortality dynamics of B. tabaci in the cotton system.
生命表提供了一种衡量种群随时间推移的出生和死亡时间表的方法。它们还可用于量化种群中的死亡来源和死亡率，这在生态学中有多种应用，包括农业生态系统。水平生命表或基于队列的生命表提供了量化种群生命率的最直接和准确的方法，因为它们跟踪种群中一组个体从出生到死亡的情况。在此，介绍了在田间进行和分析基于队列的生命表的方案，该方案利用了全球害虫烟粉虱未成熟生命阶段的固着特性。将单个昆虫定位在棉花叶片的下侧，并用无毒笔在昆虫周围画一个小圆圈进行标记。然后，可以借助手持放大镜随时间反复观察这种昆虫，以测量其从一个阶段到下一个阶段的发育情况，并确定与自然和引入的死亡力量相关的特定阶段死亡原因。分析解释了如何正确测量在每个阶段同时起作用的多种死亡力量，以及如何使用这些数据提供有意义的种群动态指标。该方法没有直接考虑成虫的存活和繁殖，这限制了对未成熟阶段动态的推断。给出了一个例子，重点是测量自下而上（植物质量）和自上而下（天敌）效应对棉花系统中烟粉虱死亡动态的影响。
