Figure 1.

Transfer strategy for selection experiment. Bacterial populations were propagated by serial transfer of 1% of the population to fresh media (represented by arrows) every 48 h. Figure shows the strategy for a single bacterial transfer step for the two control treatments and three migration treatments. Control populations were propagated by simple transfer of bacteria from one population to a fresh environment. Populations in the migration treatments consisted of two paired sub-populations. At each transfer bacteria from the source (blue line) sub-population were transferred as normal and bacteria from the focal (black line) sub-population were first mixed with bacteria from the source (blue line) sub-population at three migration rates (0.1, 1 and 10%) before being transferred.