Climate-driven selection: Climate change will fundamentally alter many aspects of the natural world. To understand how species may adapt to this change, we must understand which aspects of the changing climate exert the most powerful selective forces. Siepielskiet al.looked at studies of selection across species and regions and found that, across biomes, the strongest sources of selection were precipitation and transpiration changes. Importantly, local and regional climate change explained patterns of selection much more than did global change.Science, this issue p.959

Urban ecosystems are rapidly expanding throughout the world, but how urban growth affects the evolutionary ecology of species living in urban areas remains largely unknown. Urban ecology has advanced our understanding of how the development of cities and towns change environmental conditions and alter ecological processes and patterns. However, despite decades of research in urban ecology, the extent to which urbanization influences evolutionary and eco‐evolutionary change has received little attention. The nascent field of urban evolutionary ecology seeks to understand how urbanization affects the evolution of populations, and how those evolutionary changes in turn influence the ecological dynamics of populations, communities, and ecosystems. Following a brief history of this emerging field, this Perspective article provides a research agenda and roadmap for future research aimed at advancing our understanding of the interplay between ecology and evolution of urban‐dwelling organisms. We identify six key questions that, if addressed, would significantly increase our understanding of how urbanization influences evolutionary processes. These questions consider how urbanization affects nonadaptive evolution, natural selection, and convergent evolution, in addition to the role of urban environmental heterogeneity on species evolution, and the roles of phenotypic plasticity versus adaptation on species’ abundance in cities. Our final question examines the impact of urbanization on evolutionary diversification. For each of these six questions, we suggest avenues for future research that will help advance the field of urban evolutionary ecology. Lastly, we highlight the importance of integrating urban evolutionary ecology into urban planning, conservation practice, pest management, and public engagement.

Rates of urbanization are accelerating worldwide. The increases in temperature associated with ‘urban heat island’ effects provide both an ecological imperative and a unique opportunity to explore the ecological and evolutionary mechanisms that underlie organismal responses to rapid environmental change. We used the acorn ant, Temnothorax curvispinosus (Mayr 1866), to compare shifts in thermal tolerance of ants from rural and urban habitats throughout Cleveland, USA. Urban warming in the region has been ongoing for the past century which translates to 20 or fewer acorn ant generations. Using a common garden experiment, we found gains in the ability to withstand high temperatures and losses in the ability to withstand cool temperatures among ants in urban habitats. Owing to the greater magnitude of phenotypic change in lower compared with upper tolerances, tolerance breadth decreased in urban habitats. Mechanistically, these shifts in thermal tolerance under urbanization reflected both evolutionary change and phenotypic plasticity, as ants from urban areas exhibited higher thermal tolerances compared with ants from rural areas regardless of rearing temperature, and ants reared in the warmer temperature treatment exhibited higher tolerances than ants reared in the cooler temperature treatment. We also found evidence of evolved plasticity as the slope of the response to warmer and colder rearing environments differed significantly among rural and urban populations. While much of the ecological forecasting literature focuses on plastic responses to environmental change, our study provides evidence of rapid evolution of thermal tolerances, and suggests the importance of including evolutionary responses in forecasts of organismal responses to climatic change.

The question of parallel evolution—what causes it, and how common it is—has long captured the interest of evolutionary biologists. Widespread urban development over the last century has driven rapid evolutionary responses on contemporary time scales, presenting a unique opportunity to test the predictability and parallelism of evolutionary change. Here we examine urban evolution in an acorn-dwelling ant species, focusing on the urban heat island signal and the ant's tolerance of these altered urban temperature regimes. Using a common-garden experimental design with acorn ant colonies collected from urban and rural populations in three cities and reared under five temperature treatments in the laboratory, we assessed plastic and evolutionary shifts in the heat and cold tolerance of F1 offspring worker ants. In two of three cities, we found evolved losses of cold tolerance, and compression of thermal tolerance breadth. Results for heat tolerance were more complex: in one city, we found evidence of simple evolved shifts in heat tolerance in urban populations, though in another, the difference in urban and rural population heat tolerance depended on laboratory rearing temperature, and only became weakly apparent at the warmest rearing temperatures. The shifts in tolerance appeared to be adaptive, as our analysis of the fitness consequences of warming revealed that while urban populations produced more sexual reproductives under warmer laboratory rearing temperatures, rural populations produced fewer. Patterns of natural selection on thermal tolerances supported our findings of fitness trade-offs and local adaptation across urban and rural acorn ant populations, as selection on thermal tolerance acted in opposite directions between the warmest and coldest rearing temperatures. Our study provides mixed support for parallel evolution of thermal tolerance under urban temperature rise, and, importantly, suggests the promising use of cities to examine parallel and non-parallel evolution on contemporary time scales.