Centre for Mathematical Biology, Department of Mathematical Sciences, University of Bath, Bath BA2 7AY, UK.
J Theor Biol. 2012 Mar 21;297:103-15. doi: 10.1016/j.jtbi.2011.12.005. Epub 2011 Dec 13.
Biological invasions often damage island ecosystems. One such damaging consequence of biological invasions is hyperpredation. Hyperpredation is the increase in predation pressure from a generalist predator following the introduction of an alternative prey, typically a consequence of apparent competition between the two prey. Models for this have been devised that demonstrate this effect. However, hyperpredation may not always occur or may not always occur at the same strength. Here, we investigate how different mechanisms affect the magnitude of hyperpredation: (i) saturation of the predator's functional response, (ii) predator interference and (iii) non-predatory competition among predators. We find that all three mechanisms generally reduce hyperpredation. Predator saturation can actually overturn hyperpredation into hypopredation, an increase in native prey, as a result of apparent predation between the two prey. This occurs when the alternative prey is 'poisoned prey', i.e. prey that have a handling time cost greater than the nutritional benefit for the predator. Consuming 'poisoned prey' can result in an increase or decrease in predator density. Conversely, we also identify scenarios in which interference and competition may increase hyperpredation. Based on these insights, we conclude that the invasion of established ecosystems by non-native prey can lead to more diverse consequences than previously thought. Potential control measures should take these effects into account.
生物入侵常常会破坏岛屿生态系统。生物入侵的一个破坏性后果是超捕食作用。超捕食作用是指，随着替代猎物的引入，通常是由于两种猎物之间明显的竞争，一般捕食者的捕食压力会增加。已经设计出了用于演示这种效应的模型。然而，超捕食作用并不总是会发生，或者发生的强度也不一定相同。在这里，我们研究了不同的机制如何影响超捕食作用的程度：（i）捕食者功能反应的饱和，（ii）捕食者干扰和（iii）捕食者之间的非捕食竞争。我们发现，所有三种机制通常都会减少超捕食作用。捕食者的饱和实际上可以使超捕食作用转变为反捕食作用，即由于两种猎物之间的明显捕食作用，导致本地猎物增加。当替代猎物是“有毒猎物”时，即猎物的处理时间成本大于对捕食者的营养益处时，就会发生这种情况。食用“有毒猎物”可能会导致捕食者密度增加或减少。相反，我们还确定了干扰和竞争可能会增加超捕食作用的情况。基于这些见解，我们得出结论，非本地猎物对已建立的生态系统的入侵可能会导致比以前认为的更多样化的后果。潜在的控制措施应该考虑到这些影响。
