Urbanisation alters the natural landscape through the development of human-made habitat and is expected to influence major evolutionary processes, including nonadaptive evolution via gene flow and genetic drift. Under a neutral model of evolution, classic population genetics would suggest that small, fragmented urban populations should harbour lower genetic diversity and have greater population differentiation than nonurban areas. However, empirical support for this general prediction from landscape-level genetic and genomic studies is mixed, in part because patterns of urban evolution can be strongly moderated by attributes of the urban area being examined, or the biology of a particular focal species. Thus, it has proven challenging to extrapolate the effects of urbanisation per se on population dynamics and evolution, and a broad predictive framework through which to view the complex influence of urbanisation on evolutionary processes is still lacking. To address this gap, we develop a series of spatially- and genetically-explicit agent-based simulations to investigate how organismal traits and cityscape features contribute to shaping patterns of neutral genetic variation and structure in urban systems, including the ecological consequences of such changes for populations.
Results/Conclusions
Preliminary results indicate that extirpation in urban areas is more likely when generation time is long, dispersal ability is low, and reproduction is strictly outcrossing. This risk can be mitigated by shorter lifespans, longer dispersal distances, or self-fertilization, but each at the cost of reduced genetic diversity in urban populations. Urban populations spread across many small greenspace refugia experienced local extinction more often than those in single large greenspaces, but also exhibited higher overall genetic diversity. Both city plans resulted in similar levels of genetic differentiation between urban and nonurban populations, while narrow greenspace corridors linking urban and nonurban areas led to reduced differentiation. Notably, under many circumstances our model also indicates that urban and nonurban populations can maintain similar levels of genetic diversity for thousands of generations before developing any marked differences in allelic richness, and suggest that present-day urban populations may be in a state of constant flux. This study represents a valuable first step in moving our understanding of urban evolution and ecology forward, and empirical tests of these theoretical predictions may allow us to more clearly understand the evolutionary processes that lead to patterns seen in real-world urban environments.
