Section of Population Biology, IBED, University of Amsterdam, Science Park 904, 1098 XH Amsterdam, The Netherlands.
Oecologia. 2010 May;163(1):79-89. doi: 10.1007/s00442-010-1575-7. Epub 2010 Feb 19.
When intraguild predation is reciprocal, i.e. two predator species kill and feed on each other, theory predicts that well-mixed populations of the two species cannot coexist. At low levels of the shared resource, only the best competitor exists, whereas if the level of the common resource is high, the first species to arrive on a patch can reach high numbers, which prevents the invasion of the second species through intraguild predation. The order of invasion may therefore be of high importance in systems with reciprocal intraguild predation with high levels of productivity, with the species arriving first excluding the other species. However, natural systems are not well mixed and usually have a patchy structure, which gives individuals the possibility to choose patches without the other predator, thus reducing opportunities for intraguild predation. Such avoidance behaviour can cause spatial segregation between predator species, which, in turn, may weaken the intraguild interaction strength and facilitate their co-occurrence in patchy systems. Using a simple set-up, we studied the spatial distribution of two reciprocal intraguild predators when either of them was given priority on a patch with food. We released females of two predatory mite species sequentially and found that both species avoided patches on which the other species was resident. This resulted in partial spatial segregation of the species and thus a lower chance for the two species to encounter each other. Such behaviour reinforces segregation, because heterospecifics avoid patches with established populations of the other species. This may facilitate coexistence of two intraguild predators that would exclude each other in well-mixed populations.
当种内捕食是相互的，即两种捕食者互相捕杀和取食时，理论预测两种物种的混合种群不能共存。在共享资源水平较低的情况下，只有最好的竞争者存在，而如果共同资源的水平较高，首先到达斑块的第一种物种可以达到很高的数量，从而阻止第二种物种通过种内捕食入侵。因此，在具有高生产力和相互种内捕食的系统中，入侵的顺序可能具有重要意义，首先入侵的物种会排斥其他物种。然而，自然系统不是很好混合的，通常具有斑块状结构，这使得个体有可能选择没有其他捕食者的斑块，从而减少种内捕食的机会。这种回避行为可能导致捕食者物种之间的空间分离，从而减弱种内相互作用的强度，并促进它们在斑块状系统中的共存。我们使用一个简单的设置，研究了两种相互种内捕食者的空间分布，当其中一种在有食物的斑块上具有优先权时。我们依次释放两种捕食性螨虫的雌性，并发现两种物种都回避了其他物种居住的斑块。这导致了物种的部分空间分离，从而使两种物种相遇的机会降低。这种行为加强了隔离，因为异质种回避有其他物种定居的斑块。这可能有利于两种种内捕食者的共存，否则它们在混合种群中会相互排斥。
