图1. 关键种丧失影响食物网结构示意图。黑色箭头表示营养级关系; 红色箭头表示消费者取食力度增强。关键顶级捕食者的缺失引起生态系统下行调控机制丧失, 刺激消费者密度快速增加从而加大对生产者的取食力度, 最终导致整个食物网崩溃; 关键消费者的丧失可能阻碍营养级间的正常能量流动, 抑制捕食者的能量来源, 同时改变表观竞争格局, 导致生产者之间竞争加剧, 物种数减少; 关键生产者的丧失能够增强消费者取食其他生产者的力度, 造成生产者大量灭绝, 最终威胁消费者和顶级捕食者的生存。

Fig. 1. Schematic diagram of the impacts of loss of keystone species on food web structure. The black arrows represent trophic relationships, and the red arrows indicate the strengthened consumption by consumers. Loss of key top predators causes the absence of top-down regulation, drastically increasing consumer density and feeding intensity on producers and consequently leading to meltdown of food webs. Local extinction of key consumers may restrict energy flow between trophic levels, detrimentally affecting top predators with a simultaneous consequence of aggravating inter-specific competition among producers, which can reduce the species richness of producers. Disappearance of key producers intensifies the feeding on the remnant producers, causing the extinction of these species and in turn threatening the existence of consumers and top predators.