%0 Journal Article %A António M. M. Rodrigues %A Sylvie Estrela %A Sam P. Brown %T Community lifespan, niche expansion and the evolution of interspecific cooperation %D 2020 %R 10.1101/2020.01.02.893321 %J bioRxiv %P 2020.01.02.893321 %X Natural selection favours individuals who maximise their own reproductive success and that of their close relatives. From this perspective, cooperation that benefits individuals of a different species represents an evolutionary conundrum. The theory of mutualism seeks to resolve this puzzle, and it posits that there must be downstream benefits to cooperators that offset any costs inherently associated with interspecific cooperation. Thus, individuals should only further the survival and fecundity of their interspecific partners if this generates additional return benefits, such as food, shelter or protection. A major challenge for the evolution of mutualism is when the ecological niches of partner species overlap, as this creates a tension between the benefits of exchanging services and the costs of competing for shared resources. Here we study the extent to which niche expansion, in which cooperation augments the common pool of resources, can resolve this problem. We find that niche expansion facilitates the evolution of mutualism, especially when populations are at high densities. Further, we show that niche expansion can promote the evolution of reproductive restraint, in which a focal species adaptively sacrifices its own growth rate to increase the density of partner species. We interpret these results in the context of microbial community interactions, which are often characterized by yield-enhancing exchanges of nutrients, termed ‘cross-feeding’. Our findings suggest that yield-enhancing mutualisms are more prevalent in stable habitats with a constant supply of resources, where populations typically live at high densities, but such mutualisms are particularly vulnerable to the emergence of cheats. In general, our findings highlight the need to integrate both temporal and spatial dynamics in the analysis of mutualisms. %U https://www.biorxiv.org/content/biorxiv/early/2020/01/03/2020.01.02.893321.full.pdf