New research shows how bacteria evolve to increase ecosystem functioning by recycling each other's waste. The study provides some of the first evidence for how interactions between species shape evolution when there is a diverse community. Predicting how species and ecosystems will respond to new environments is an important task for biology. However, most studies of evolutionary adaptation have considered single species in isolation, despite the fact that all species live in diverse communities alongside many other species. Recent theories have suggested that interactions between species might have a profound effect on how each species evolves, but there has been little experimental support for these ideas.

The research, published May 15 in the online, open-access journal PLoS Biology, involved culturing five bacterial species in the laboratory, studying them both in isolation and mixed together in a community of all five species. Cultures were allowed to adapt to new conditions over seventy bacterial generations. The feeding habits of each species were then measured using chemical analyses; by comparing chemical resource use at the start and end of the experiment, it was possible to show how the resource use and waste production of each species had evolved.

The research team, from Imperial College London, found that bacteria that evolved in a mixed community with other species altered their feeding habits to share resources more effectively amongst themselves and to make use of each other's waste products in a cooperative manner. In contrast, when grown alone, the same species evolved to use the same resources as each other, thereby competing and impairing（损害，削弱） each other's growth.

The changes in feeding habits led to a greatly improved functioning of the community of species as a whole. Communities that were reassembled with bacteria that previously evolved together were better, collectively, at breaking down resources than those reassembled with bacteria that had previously evolved in isolation. Together, the results show that the way in which species adapt is greatly altered by the presence of other species, and that co-evolution enhances the ecological functioning of groups of species.