Zombie ants: Parasite manipulation of host behavior

Certain parasites adaptively manipulate host behavior. Recently researchers interested in manipulative strategies have moved beyond an adaptationist framework to a more integrative approach that seeks to understand the behavioral ecology of manipulative parasites. I will review this field before focusing on lessons learnt from behavioral manipulators inside social insect societies. In my primary study system, Ophiocordyceps unilateralis in Carpenter ants, worker behavior is changed causing individual ants to abandon the nest and die under leaves. The death grip, whereby ants bite major veins, fixes individuals to leaves and prevents dislodgement following ant death. The fungi inside dying ants expresses a choice of leaf and leaf topology and uses either a solar or magnetic cue to orient the dying ant. The mechanisms of this manipulation are under investigation and here I report on the effects of fungal infection of muscle physiology and motor coordination. Besides the ant body as ecology (shaping fungal behavior), the relevant ecologies are the leaves to which dying ants attach and colony of non-infected (sibling) ants from which the manipulated individual came. I will discuss the basis of immunity by plants and non-infected kin towards zombie ants and ask the more general question of how the evolution of fungal behavior, via ant muscles, is affected also by the location of nests and leaves in tropical rainforests.