Fig. 3: Coevolution from antagonism to mutualism in the two-plant species community.

Panels (a, b) show interaction outcomes 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 line in panel a and is extinct below. There is no dashed gray line in panel b because the ancestral insect can persist on the ancestral D. wrightii alone. 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 separating the interaction breakdown boundary (solid black line) and the interaction transition boundary (dotted black line), as depicted by green arrows. Simultaneously, coevolution of attraction and defense drives the transition to net mutualism, as depicted by orange arrows from ancestral coESS (white points) to the new coESS (black points). Blue points give empirical estimates of the coESS (panel (a): h_w = 1 ± 0.4; v_w = 4.3 ± 0.6; panel (b): h_d = 2 ± 0.8; v_d = 2.3 ± 0.4), where the crossbars show variation in leaf consumption³⁰ and the standard error of floral visitation¹⁹ (n = 89 plants for D. wrightii; n = 33 plants for D. discolor) (Methods). While the plant species coevolve in the model (see Supplementary Movie 3), panels (a, b) are plotted with the other plant species held at its final coESS for clarity. Panels (c, d) 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 (e, f) plot the coevolutionary dynamics of pollination benefits (b_i; black lines), attraction (v_i; blue lines) and defense (h_i; purple lines).