Fig. 4: Coevolutionary transitions in more generalized trophic interactions.

Interaction outcomes in the presence of an alternative larval host plant (panels a, b) or an alternative nectar source (panels c, d) are plotted as a function of attraction (v_i) and defense (h_max – h_i), where h_max is the maximum herbivory rate. The ancestral insect persists as a pure antagonist above the dashed gray lines and is extinct below. The insect persists as a net antagonist within the gray regions and is extinct within the white regions. Plant evolution of pollination benefits (b_i > 0) expands the green mutualistic regions by moving the interaction breakdown boundary (solid black line) away from the interaction transition boundary (dotted black line), as depicted by green arrows (see Supplementary Movies 4 and 5). Simultaneously, coevolution of attraction and defense drives the transition to net mutualism, as depicted by orange arrows from ancestral coESSs (white points) to new coESSs (black points). Empirical estimates of the coESSs are not included due to data limitations. Panels (e–h) plot the equilibrium densities of each Datura species (solid green lines) and insect larvae per plant of each Datura species (dashed green lines) over evolutionary time, τ. Panels (i-l) plot the coevolutionary dynamics of pollination benefits (b_i; black lines), attraction (v_i; blue lines), and defense (h_i; purple lines).