Speciation and the City.

Many outstanding questions about speciation are difficult to test empirically because of a lack of suitable study systems. Here, we highlight studies of evolutionary ecology in urban environments to argue that cities provide ideal conditions that can be leveraged to study the speciation process. Considering general findings from these studies, we discuss the mechanisms of speciation that are likely to occur in cities. We also discuss fundamental questions about speciation that urban environments are uniquely suited to address, such as those about the earliest stages of divergence or the role of phenotypic plasticity. We conclude that the study of contemporary speciation in urban environments has promise to facilitate discoveries about the process of speciation as it occurs in the Anthropocene.