The molecular and biochemical mechanisms involved in maintaining biodiversity are largely unknown. In 11 July Nature, Benjamin Kerr and colleagues from Stanford University, show that localized interactions that mimic the game "rock-paper-scissors" promotes biodiversity in real-life (Nature 2002, 418:171-174).

Kerr et al. used a non-transitive model community containing several strains of Escherichia coli — strains that can produce a toxin, or not and strains that are resistant to a toxin, or not. They observed that diversity is rapidly lost in this experimental community when dispersal and interaction occur over relatively large spatial scales — in this case the organisms producing the antidote but no toxin win out. But, where ecological processes are localized all populations coexist.

These results "open new vistas for understanding how biological communities are build up – one of the most intriguing aspects of the study of biodiversity," write Martin Nowak and...