The rapid spread of antibiotic resistance challenges modern medicine. So far, mechanistic and quantitative knowledge concerning the spread of resistance genes mainly relies on laboratory experiments with simplified setups, e.g. two strain communities. Thus, the transferability of the obtained process rates might be limited. To investigate the role of a diverse community concerning the dissemination of the multidrug resistance plasmid RP4, an Escherichia coli harboring RP4 invaded a microbial community consisting of 21 species. Changes in the community composition as well as plasmid uptake by community members were monitored for 22 days. Special focus was laid on the question of whether the observed changes were dependent on the actual invading donor isolate and the ambient antibiotic concentration. In our microcosm experiment, the community composition was primarily influenced by the given environmental variables and only secondarily by the particular invader E. coli. The establishment of resistance within the community, however, was directly dependent on the donor identity. The extent to which ambient conditions influence the spread of RP4 depended on the E. coli donor strain. These results emphasize that even within one species there are great differences in the ability to conquer an ecological niche and to spread antibiotic resistance.