Competitive coexistence through intermediate polyphagy

Communities containing species that are not niche differentiated require some mechanism to avoid the expected competitive exclusion of all but one or a few species. Predator pressure has long been held to be one of those mechanisms. Here, we show that the critical feature of predation is not its intensity, but its degree of specialization. Neither highly specialist nor highly generalist predators are effective at deterring competitive exclusion, but rather predators that exhibit an intermediate level of polyphagy can effectively provide such a mechanism.