图2. 外来物种入侵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或捕食者捕食强度增强。入侵捕食者在竞争排除同营养级中乡土种的同时由于其捕食偏好改变消费者表观竞争格局并影响低营养级; 入侵消费者通过竞争减少消费者物种数对生产者产生较大的取食压力, 同时阻断顶级捕食者的食物来源, 进而破坏食物网的上行和下行调控, 改变食物网结构; 在缺乏消费者取食的情况下, 入侵生产者通过竞争排除其他生产者并阻断能量流动, 导致消费者与捕食者灭绝, 引发整个食物网的崩溃。

Fig. 2. Schematic diagram of the impacts of alien invasive species on food web structure. The black arrows represent trophic relationships, and the red arrows indicate the increased consumption or the strengthened predation. Invasive predators can exclude native predators by competition and alter the interspecific competition of consumer due to their feeding preference, impacting the species composition at lower trophic levels. Invasive consumers exclude native consumers, intensify feeding on some producers and restrict food resources of top predators, disturbing top-down and bottom-up regulations and changing food web structure. In the absence of natural enemies, invasive producers exclude native producers and cut off energy flow, leading to massive extinction of consumers and top predators and meltdown of food webs.