Theoretical studies have shown that in protection mutualism, modification of top-down control by protectors may be destabilizing. Central to this prediction are the assumptions that 1) protection mutualism increases the abundance of protected partners, 2) this increased abundance generates a lagged effect on partner resources, and 3) spatial dynamics can be ignored. Although a number of studies have confirmed that protection mutualism can increase the abundance of protected herbivores, the evidence for a negative effect...