Coinfection outcomes of Regiella strains. Each dark gray line in the figures represents a separate aphid line, tracked for 8 generations shown along the x-axis. Injections with strain. LSR are shown in the top panel, and injections with strain .313 are shown in the bottom panel. Within each panel, recipient aphids either harbored no secondary symbionts (symbiont-free aphids) or harbored Regiella of the opposite strain from that which was injected. Vertical movement on the plots represents the outcome of PCR screens for Regiella. Injections into symbiont-free aphids were either retained or lost at each generation. Coinfections with two Regiella strains were either maintained as coinfections, or one of the symbiont strains was lost, as indicated to the right of the figure. Note that at each generation, a single aphid from each host plant was harvested at random for DNA extraction and PCR screening—lines therefore can “regain” a symbiont across generations due to individual differences among aphids on a plant.