Abrams Peter A
Department of Zoology, University of Toronto, 25 Harbord Street, Toronto, Ontario M5S 3G5, Canada.
Am Nat. 2002 Sep;160(3):293-305. doi: 10.1086/341521.
Several models are used to show that population sizes are often relatively insensitive to deteriorating environmental conditions over most of the range of environments that allow population persistence. As conditions continue to worsen in these cases, equilibrium population sizes ultimately decline rapidly toward extinction from sizes similar to or larger than those before environmental decline began. Consumer-resource models predict that equilibrium or average population size can increase with deteriorating environmental conditions over a large part of the range of the environmental parameter that allows persistence. The initial insensitivity or increase in the population of the focal species occurs because changes in the populations of other components of the food web compensate for the decline in one or more fitness components of the focal population. However, the compensatory processes are generally nonlinear and often approach their limits abruptly rather than gradually. When there is steady directional change in the environment, populations lag behind the equilibrium population size specified by current environmental conditions. The environmental variable can then decline below the level required for population persistence while the population size is still close to or greater than its original value. Efficient consumers and self-reproducing resources are especially likely to produce this outcome. More complex models with adaptive behavior, additional consumers, or additional resources often exhibit similar trajectories of population size under environmental deterioration.
有几种模型被用来表明，在大多数能使种群持续存在的环境范围内，种群规模通常对不断恶化的环境条件相对不敏感。在这些情况下，随着条件持续恶化，平衡种群规模最终会从与环境恶化开始前相似或更大的规模迅速下降至灭绝。消费者 - 资源模型预测，在能使种群持续存在的环境参数范围的很大一部分内，平衡或平均种群规模会随着环境条件的恶化而增加。目标物种种群最初的不敏感或增加是因为食物网中其他组成部分的种群变化补偿了目标种群一个或多个适合度组成部分的下降。然而，补偿过程通常是非线性的，而且往往会突然接近其极限，而不是逐渐接近。当环境存在稳定的定向变化时，种群会落后于当前环境条件所规定的平衡种群规模。然后，在种群规模仍接近或大于其原始值时，环境变量可能会降至种群持续存在所需的水平以下。高效的消费者和自我繁殖的资源尤其可能产生这种结果。具有适应性行为、额外消费者或额外资源的更复杂模型，在环境恶化时往往表现出类似的种群规模轨迹。
