Urban evolution comes into its own: Emerging themes and future directions of a burgeoning field

Abstract

Urbanization has recently emerged as an exciting new direction for evolutionary research founded on our growing understanding of rapid evolution paired with the expansion of novel urban habitats. Urbanization can influence adaptive and nonadaptive evolution in urban-dwelling species, but generalized patterns and the predictability of urban evolutionary responses within populations remain unclear. This editorial introduces the special feature "Evolution in Urban Environments" and addresses four major emerging themes, which include: (a) adaptive evolution and phenotypic plasticity via physiological responses to urban climate, (b) adaptive evolution via phenotype-environment relationships in urban habitats, (c) population connectivity and genetic drift in urban landscapes, and (d) human-wildlife interactions in urban spaces. Here, we present the 16 articles (12 empirical, 3 review, 1 capstone) within this issue and how they represent each of these four emerging themes in urban evolutionary biology. Finally, we discuss how these articles address previous questions and have now raised new ones, highlighting important new directions for the field.

Keywords: Anthropocene; cities; eco‐evolutionary dynamics; gene flow; urban adaptation.

Figure 1

Researchers use a wide variety of metrics to describe urban habitats, and different metrics are appropriate for different species and to address different questions. The 12 empirical papers in this special issue used the following metrics to describe urbanization and to analyze phenotypic and genotypic variation: land cover and use, impervious surface cover (ISA) and roads, temperature, human population density, built‐up land cover, and proximity to the city center or within metropolitan boundaries (gray boxes indicate the metric(s) used in each study)

Figure 2

We identified four focal topics from the empirical contributions (population genetics—yellow, trait–environment relationships—pink, human–wildlife interactions—purple, physiology—blue) as well as emerging themes from the reviews and capstone paper (green). These five themes are presented here with the top 19 words from the abstracts, with word size relative to the prevalence across the abstracts in each group

Figure 3

This special issue includes empirical work from four main themes related to evolution in response to urbanization. (a) Adaptive evolution of physiology: Chick et al. (2020) found acorn ants exhibit elevated metabolic rates, but this difference diminishes under acute thermal stress and is associated with increased resource acquisition. Top: Acorn Ants, Temnothorax curvispinosus, Lauren Nichols; bottom: modified figure 2A from Chick et al. (2020). (b) Adaptive evolution of trait–environment relationships: Corsini et al. (2020) examined relationships between impervious surface cover (ISA) and growth rate, body size, and survival, finding strong selection on body size in habitats with more impervious surface cover. Top: Parus major, Michela Corsini; bottom: modified figures 3 and 4 from Corsini et al. (2020). (c) Population Genetics: Wang (2020) found bottlenecks occurred in all populations prior to recent urbanization, but there was genetic structure along the urban to rural gradient. Top: Pelophylax plancyi, photo credit Wei Xu; bottom: modified figure 4 from Wang (2020). (d) Human–wildlife interactions: Schell, Stanton, et al. (2020) presents a perspective that integrates human–wildlife interaction, wildlife management and urban evolution to address how organisms adapt to urban environments while experiencing socio‐ecological processes. Top: Racoons, Procyon lotor, Zachary Hawn; bottom: modified figure 4 from Schell, Stanton, et al. (2020)