Urban Landscape Genetics: Are Biologists Keeping Up with the Pace of Urbanization?

Urbanization has the potential to jeopardize the sustainability of populations of organisms living within and dispersing across urban areas. Landscape genetics approaches offer a great promise for quantifying how urban features affect ecological and evolutionary processes for species living within and around cities. In this review, we assess the current state (2015–2020) of urban landscape genetics research, examining what types of urban features are quantified, what genetic measures are used, what species are studied, and in which geographic regions they are conducted. We then make recommendations for future research. We identified relatively few landscape genetic studies conducted within urban areas published in the last 5 years. We also found a publication bias towards certain taxa and geographic regions (mainly mammals studied in North America), based on results from relatively few molecular markers. These studies used varied measures of urbanization in their analysis, but the most common was urban land use/land cover measured at different resolutions, followed by buildings/development and transportation infrastructure (roads, railroads, and tramways). The results of these studies reflect previously conducted urban research findings that urban features may inhibit, facilitate, or have no correlation with gene flow, usually a product of which focal taxa is being studied, as well as what urban features are present/measured within variable cityscapes. We urge future research to directly measure urban features and stress the need for explicitly sampling within and around urban areas to gain full understanding of whether urbanization impedes, facilitates, or does not affect genetic differentiation between populations. To facilitate the development of robust theory, we urge the formation of a global network of urban landscape geneticists to collaborate and sample diverse taxa, in varied global landscapes and climates, and analyze genome-wide datasets for more robust conclusions about gene flow and genetic diversity. We advocate for analyzing urban features at multiple scales to allow broad conclusions about the effects of urbanization across studies, taxa, and regions. Finally, we recommend that study designs include social, cultural, and economic differences in human land use, which have the potential to affect how species disperse, survive, and reproduce in urban areas. Taking these factors into account, we can make novel advances in understanding how complex urban landscapes shape contemporary evolution.