The role of demographic stochasticity for the formation of species

In individual-based models of competing, reproducing, and evolving organisms one finds that, with high mutation rates, organisms fill nichespace evenly rather than being assignable to ecologically distinct species. We analyzed mathematically the general conditions under which this even filling gives way to species formation. Surprisingly, the transition is driven by demographic stochasticity, implying that for numerically highly abundant organisms it can be suppressed. Indeed, we find indications for the breakdown of species formation in environmental genetic data sets for small, abundant organisms.