As we know, the landscape of urban areas is changing rapidly as land is converted from natural to anthropogenic space. Additionally, new technology has allowed us to collect more data at a lower cost than ever before. The combination of these two events led my co-authors and me to ask “Are biologists keeping up with the pace of urbanization?” in a recent review article published in Current Landscape Ecology Reports.
In this article we reviewed the state of urban landscape genetics over the past five years and found bias in:
- Geographic Distribution of Studies
- Taxa Sampled
- Molecular Marker Type
- Multicity comparisons
- Urban Landscape Features Measured
Geographic Distribution of Studies
Of the 32 publications, we found that over half of the studies (n=15) were conducted in North America and Europe. This was disappointing given the rapid increase of urbanization in South America, Asia, and Africa. Studies in these regions would also allow researchers to compare the landscape “before” and “after” urbanization as cities in these regions are expanding.
Taxa Sampled
We found a heavy bias towards studies of mammals with half the studies published in the past five years examining the effects of urban landscapes on mammals. We think this reflects a bias in funding and publication since mammals are often viewed as more charismatic than other taxa. We call upon researchers to conduct urban landscape genetics studies on non-mammalian taxa to increase the breadth of knowledge and help us understand the universality of the effect of urbanization on landscape genetics.
Additionally, we found that very few non-native organisms were studied. While we understand the desire to study organisms in their native range, we think there is value in examining non-native organisms, especially human commensals that thrive in cities.
Molecular Marker Type
Most of the papers we examined for our review used microsatellite markers to examine genetic diversity. While some of these studies also included SNP markers sequenced via Sanger sequencing, only three utilized next-generation sequencing. With the decreasing cost of high throughput sequencing, we see tremendous value in this technology to provide greater insight into urban landscape genetic patterns.
Multicity Comparisons
Urban landscape genetics currently lacks multicity comparisons of dispersal and gene flow patterns. These comparisons are essential to determine if the observed barriers are local or universal.
Urban Landscape Features Measured
One of the largest challenges with current landscape genetics models is the lack of landscape data. We found that many researchers used the National Land Cover Database or the Copernicus Land Monitoring Service’s Land Cover, and while these datasets are essential, they are often collected at scales that are not biologically relevant. For example, the National Land Cover Database has a 30-meter by 30-meter grid, which is likely fine when studying pigeon landscape genetics but may be less relevant for studying the landscape genetics of small organisms such as ants. City-collected data like New York City’s 6 inch Land Cover Raster Data, when available, is a great option and we call on more cities to produce these types of datasets.
We also recognize that the landscape is shaped not only by contemporary land use but historic land use and social variables. With that, we think it is essential for urban landscape genetics researchers to incorporate socioeconomic variables (e.g. income, transportation routes, restaurant locations, garbage pickup frequency, etc.) when studying urban landscape genetics.
Want to find out more? Check out the full paper here:
Featured Image: Conceptual diagram illustrating the current state of urban landscape genetics research and the recommendations for future research programs. The inner dashed circle visualizes the current state of urban landscape genetics research, which is heavily biased towards studies of mammals (green), single cities (pink), urban metrics that are often limited to roads and development (yellow), microsatellites (blue), and North America (orange). The outer circle represents our recommendations for future research, including a greater diversity of taxa (green); comparison of multiple cities with different socioeconomic demographics (pink); the inclusion of multiple measures of urbanization including socioeconomic metrics (yellow); the use of genome-wide SNP datasets (blue); and a focus on Asia, Africa, and South America where urbanization is accelerating at the most rapid rates. Image from Fusco et al. (2021).
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