Host fitness and context dependency in defensive symbiosis.

<p>Average host fitness with or without a protective symbiont in relation to risk of attack. Defensive mutualism assumes that the symbiont improves host fitness in the presence of the enemy (h = 1), however the symbiont itself may (A) or may not (B) incur a fitness cost for the host in the absence of the enemy (h = 0).</p

Individual sheep reactions to ergoty feed.

<p>Single rams' (A–F) actions relating to ergot-containing feed on different rounds of a food choice test. The column colours indicate the proportion of actions within trials: white, ergoty feed not approached; grey, ergoty feed rejected; black, ergoty feed chosen.</p

Overall reaction of sheep to ergoty feed.

<p>A decision tree representing the average probabilities of rams' (n = 6) approaches and decisions between ergoty and control forage in a food choice test. The final choice signifies the alternative eventually chosen for eating.</p

Effect of ergot on host fitness.

<p>Parameter space where ergot infection has a positive (below the lines) or negative (above the lines) net effect on host fitness. β = relative loss of seeds due to ergot infection, d = protective effect of ergot infection, hα = cost of herbivory.</p