This dataset describes the composition of a co-evolving community (as colony forming units) over a 30-transfer selection experiment in soil microcosms. The community consists of Pseudomonas fluorescens SBW25 + Pseudomonas putida KT2440 + plasmid pQBR57. Full details about this dataset can be found at https://doi.org/10.5285/9da9bf05-fdbf-41f9-8591-1a4af9b84000