Figure 3 : Ecological context affects the factors of the ERH. Three of the seven contexts (time, A-C; relative resource availability, D-F; phylogenetic relatedness, G-I) are shown for brevity, and how these contexts affect the processes of changing enemy impact (A, D, G), changing enemy diversity (B, E, H), and host adaptation (C, F, I). Trajectories are drawn assuming that the other two processes are held constant, though there may be complex feedbacks between them. For example, evolutionary changes to the growth-defence trade-off under different resource regimes will alter the relative impact of enemies through time. These are predictions but other trajectories are possible: we aim to demonstrate generally how context interacts with factors to drive the likelihood of the ERH occurring, and its strength.