Dewi Sonya, Chesson Peter
Ecosystem Dynamics Group, Australian National University, Canberra, Australia.
Theor Popul Biol. 2003 Nov;64(3):331-43. doi: 10.1016/s0040-5809(03)00094-7.
The lottery model of competition between species in a variable environmental has been influential in understanding how coexistence may result from interactions between fluctuating environmental and competitive factors. Of most importance, it has led to the concept of the storage effect as a mechanism of species coexistence. Interactions between environment and competition in the lottery model stem from the life-history assumption that environmental variation and competition affect recruitment to the adult population, but not adult survival. The strong role of life-history attributes in this coexistence mechanism implies that its robustness should be checked for a variety of life-history scenarios. Here, age structure is added to the adult population, and the results are compared with the original lottery model. This investigation uses recently developed shape characteristics for mortality and fecundity schedules to quantify the effects of age structure on the long-term low-density growth rate of a species in competition with its competitor when applying the standard invasibility coexistence criterion. Coexistence conditions are found to be affected to a small degree by the presence of age structure in the adult population: Type III mortality broadens coexistence conditions, and type I mortality makes them narrower. The rates of recovery from low density for coexisting species, and the rates of competitive exclusion in other cases, are modified to a greater degree by age structure. The absolute rates of recovery or decline of a species from low density are increased by type I mortality or early peak reproduction, but reduced by type III mortality or late peak reproduction. Analytical approximations show how the most important effects can be considered as simple modifications of the long-term low-density growth rates for the original lottery model.
在可变环境中物种间竞争的抽签模型，对于理解波动的环境因素与竞争因素之间的相互作用如何导致共存现象，具有重要影响。最为重要的是，它引出了存储效应这一物种共存机制的概念。抽签模型中环境与竞争的相互作用源自生活史假设，即环境变异和竞争影响成年种群的补充，但不影响成年个体的存活。生活史特征在这种共存机制中发挥的重要作用表明，应当针对各种生活史情形检验其稳健性。在此，将年龄结构添加到成年种群中，并将结果与原始抽签模型进行比较。本研究运用最近开发的死亡率和繁殖力时间表的形状特征，在应用标准入侵性共存标准时，量化年龄结构对一个物种与其竞争者竞争时长期低密度增长率的影响。发现共存条件受成年种群中年龄结构的影响较小：III型死亡率拓宽了共存条件，而I型死亡率则使其变窄。共存物种从低密度恢复的速率，以及其他情况下竞争排斥的速率，受年龄结构的影响更大。一个物种从低密度恢复或下降的绝对速率，因I型死亡率或早期繁殖高峰而增加，但因III型死亡率或晚期繁殖高峰而降低。分析近似结果表明，如何将最重要的影响视为对原始抽签模型长期低密度增长率的简单修正。
