Data from: Cheating and resistance to cheating in natural populations of the bacterium Pseudomonas fluorescens

Bacteria perform cooperative behaviours that are exploitable by non-cooperative cheats, and cheats frequently arise and coexist with cooperators in laboratory microcosms. However, evidence of competitive dynamics between cooperators and cheats in nature remains limited. Using the production of pyoverdine, an iron-scavenging molecule, and natural soil populations of Pseudomonas fluorescens, we found that (1) non-producers are present in the population; (2) they co-occur (<1cm3) with pyoverdine producers; (3) they retain functional pyoverdine receptors and (4) they can utilize the pyoverdine of on average 52% of producers. This suggests non-producers can potentially act as social cheats in soil: utilizing the pyoverdine of others while producing little or none themselves. However, we found considerable variation in the extent to which non-producers can exploit cooperators, as some cooperators appear to produce exclusive forms of pyoverdine or kill non-producers with toxins. We examined the consequences of this variation using theoretical modeling. Variance in exploitability leads to some cheats gaining increased fitness benefits and others decreased benefits. However, the absolute gain in fitness from high exploitation is lower than the drop in fitness from low exploitation, decreasing the mean fitness of cheats and subsequently lowering the proportion of cheats maintained in the population Our results suggest that although cooperator-cheat dynamics can occur in soil, a range of mechanisms can prevent non-producers from exploiting cooperators.