Author response image 1. Adapted from Figures 1 and 6 in (Shou et al. 2007): When partner $G_{\to L}^{\leftarrow A}$ was paired with the cooperator $R_{\to A}^{\leftarrow L}$, the coculture grew from low to high densities. No persistent growth was observed when partner $G_{\to L}^{\leftarrow A}$ was paired with the cheater $C^{\leftarrow L}$.