FIG 4 .

Costs and benefits of horizontally acquiring a competitor’s T6SS. In this model of competition between two bacterial strains, one (the “recipient”) was capable of integrating T6SS alleles from the other (the “competitor”). High rates of HGT were adaptive only when the recipient strain faced a competitor with superior T6SS alleles. For plotting purposes, relative fitness of >2 was clipped. Simulations were run for 15,000 time steps. Time-lapse videos of these fitness landscapes are shown in Movies S2 and S3.