Tikhonov, Mikhail2016-08-092016Tikhonov, Mikhail. 2016. “Community-level cohesion without cooperation.” eLife 5 (1): e15747. doi:10.7554/eLife.15747. http://dx.doi.org/10.7554/eLife.15747.2050-084Xhttp://nrs.harvard.edu/urn-3:HUL.InstRepos:27822342Recent work draws attention to community-community encounters ('coalescence') as likely an important factor shaping natural ecosystems. This work builds on MacArthur’s classic model of competitive coexistence to investigate such community-level competition in a minimal theoretical setting. It is shown that the ability of a species to survive a coalescence event is best predicted by a community-level 'fitness' of its native community rather than the intrinsic performance of the species itself. The model presented here allows formalizing a macroscopic perspective whereby a community harboring organisms at varying abundances becomes equivalent to a single organism expressing genes at different levels. While most natural communities do not satisfy the strict criteria of multicellularity developed by multi-level selection theory, the effective cohesion described here is a generic consequence of resource partitioning, requires no cooperative interactions, and can be expected to be widespread in microbial ecosystems. DOI: http://dx.doi.org/10.7554/eLife.15747.001en-USmicrobial ecologyconsortiacooperationresource competitionniche constructionNoneJournal Article2016-08-0910.7554/eLife.15747