Global relationships between body size and urban affinity across more than 30,000 plant and animal species
- Department of Wildlife Ecology and Conservation, Fort Lauderdale Research and Education Center, Institute of Food and Agricultural Sciences, University of Florida, United States
- UK Centre for Ecology and Hydrology, United Kingdom
- Department of Biology, Georgetown University, United States
- Marine and Environmental Biology Section, Department of Biological Sciences, University of Southern California, United States
- Research Centre for Ecological Change, Faculty of Biological and Environmental Sciences, University of Helsinki, Finland
- Department of Biology, University of Turku, Finland
- Institute of Biology, Leipzig University, Germany
- German Centre of Integrative Biodiversity Research (iDiv), Germany
- Department of Ecology and Evolutionary Biology, Yale University, United States
- Center for Biodiversity and Global Change, Yale University, United States
- Wildness, Biodiversity and Ecosystems under Change (WILD), Department of Biology, Vrije Universiteit Brussel, Belgium
Figures
Figure 1
Conceptual framework illustrating hypothesized mechanisms linking urban affinity to interspecific body-size shifts.
These include dispersal and mobility constraints under habitat fragmentation (Merckx and Van Dyck, 2019; Callaghan et al., 2019), thermophily and the temperature–size rule driven by the urban heat island effect (Merckx et al., 2018b; Piano et al., 2017), size-biased competition and survival (Sand-Jensen et al., 2018; Everingham et al., 2019), and size-biased human preferences (Williams et al., 2009). Urban fragmentation of habitat resources can select for increased mobility (e.g. larger butterflies) or reduced mobility (e.g. larger seeds) depending on isolation severity. Elevated urban temperatures favor thermophily, which often negatively correlates with size as it affects the heat balance via thermal inertia. Similarly, these higher temperatures generally favor smaller-bodied adult ectotherms because they accelerate development and reduce time available for growth (i.e. temperature-size rule). In plants, the increased CO2 and nutrient availability associated with anthropogenic environments—due to heating- and traffic-related CO2 emissions and eutrophication—provides a competitive advantage to larger plant species, and human preferences too may favor larger species (e.g. tree-lined streets), whereas smaller species may be advantaged in colonizing built infrastructure.
Figure 2 with 11 supplements
Species urbanness distributions (SUDs) exemplified for eight subrealms.
Plotted are all species per subrealm (A), with the images highlighting an example ‘hyper-exploiter’ species from each of these subrealms (i.e. with a high urban affinity score). The x-axis shows the urban affinity measure, whereas the y-axis is the number of species within that bin. There were consistent patterns for kingdoms, classes, and orders (B) as shown by similar central tendencies despite variation in distributional shape. The vertical dashed line represents where species are neutral towards urbanization. Photos: Brown rat (Ouwesok), Monk parakeet (Juan Emilio), Cape dwarf chameleon (Berkeley Lumb), American cockroach (Len Worthington), Flaming katy (Lyubo Gadzhev), Juno silverspot (Rigoberto Ramírez Cortés, CC BY 4.0), Hibiscus harlequin bug (Sam Fraser-Smith, CC BY 4.0), and Mascarene island leaf-flower (Douglas Goldman).
© 2019, Ouwesok. Brown rat image acquired from flickr and background was removed by authors (published under a CC BY-NC licence). Further reproductions must adhere to the terms of this license.
© 2011, Juan Emilio. Monk parakeet image acquired from flickr and background was removed by authors (published under a CC BY-SA licence). Further reproductions must adhere to the terms of this license.
© 2023, Berkeley Lumb. All Rights Reserved. Cape dwarf chameleon image acquired from iNaturalist and background was removed by authors. Further reproduction of this illustration would need permission from the copyright holder.
© 2017, Len Worthington. American cockroach image acquired from flickr and background was removed by authors (published under a CC BY-SA licence). Further reproductions must adhere to the terms of this license.
© 2026, Lyubo Gadzhev. Flaming katy image acquired from NC State Extension and background was removed by authors (published under a CC BY-SA licence). Further reproductions must adhere to the terms of this license.
© 2023, Douglas Goldman. Mascarene island leaf-flower image acquired from iNaturalist and background was removed by authors (published under a CC BY-SA licence). Further reproductions must adhere to the terms of this license.
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Figure 2—source data 1
The urban affinity values (N=56,181 total values (i.e., unique urban affinity score in a subrealm)) for potential inclusion in our analysis.
- https://cdn.elifesciences.org/articles/109047/elife-109047-fig2-data1-v1.zip
Figure 2—figure supplement 1
We used subrealms as our geographical aggregation.
Subrealms were quantified from aggregating bioregions as identified by One Earth (see more here: https://www.oneearth.org/bioregions/). The subrealms level was chosen after exploring the tradeoff between accounting for geographic differences in urban affinity and the number of species that could be included.
Figure 2—figure supplement 2
Violin plots showing the distribution of urban affinity values by kingdom across the 12 subrealms with the greatest sample sizes.
Figure 2—figure supplement 3
Violin plots showing the distribution of urban affinity values by class across the 12 subrealms with the greatest sample sizes.
Only classes represented by ≥ 50 species within a subrealm are included.
Figure 2—figure supplement 4
Violin plots showing the distribution of urban affinity values by order across the 9 subrealms with the greatest sample sizes.
Only orders represented by ≥ 50 species within a subrealm are included.
Figure 2—figure supplement 5
An illustration of the species-specific distribution of observations and the VIIRS values, in average radiance, of those observations for six different species within the Great European Forests subrealm.
Of note is that the urban affinity is not shown, as some are negative values, but these values are shown in the text.
Figure 2—figure supplement 6
The distribution of Magnolia warbler Setophaga magnolia observations and the VIIRS values, in average radiance, of those observations in four different subrealms.
Shown using dashed lines are the species-specific mean (green), the subrealm-specific mean of VIIRS (violet), and the resulting urban affinity measure (yellow).
Figure 2—figure supplement 7
The total number of species for which we calculated urban affinity scores, stratified by subrealm and shown separately for Animalia (top) and Plantae (bottom).
The subrealms with their names are shown in Figure 2—figure supplement 1. The dataset of species’ urban affinity scores is provided in Appendix 2—table 1.
Figure 2—figure supplement 8
The total number of subrealms for which a species had an urban affinity score.
The majority of species (64%) only had an urban affinity score from one subrealm, but the range was from 1 to 34.
Figure 2—figure supplement 9
An illustrative example, showing the relative urban affinity scores for Hymenoptera in the Northeast American Forests subrealm.
The plot is for illustrative purposes and the values for each species can be found in Appendix 2—table 1.
Figure 2—figure supplement 10
An illustrative example, showing the relative urban affinity scores for Lepidoptera in the Southeast Asian Forests subrealm.
The plot is for illustrative purposes and the values for each species can be found in Appendix 2—table 1.
Figure 2—figure supplement 11
An illustrative example, showing the relative urban affinity scores for Asterales in the Scandinavia and West Boreal Forests subrealm.
The plot is for illustrative purposes and the values for each species can be found in Appendix 2—table 1.
Figure 3 with 5 supplements
Effect sizes between body size and urban affinity across the tree of life and individual effect sizes for animals and plants families.
(A) Effect sizes of the relationship between body size and urban affinity for the 371 families included in our analysis, plotted along a phylogenetic tree of life (see Methods); Plantae are highlighted and shaded in green. Colors indicate the direction of the effect: orange indicates negative, petrol indicates positive, grey indicates neutral (i.e. any effect sizes between –0.05 and 0.05). (B, C) Histograms of individual effect sizes for each family, for animals (B) and plants (C). Orders are shown along the outside edge of the phylogenetic tree, each with a bar and icon, for any order with more than three families. An interactive version for full exploration of our results at both family and order level is available here.
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Figure 3—source data 1
A list of the final potential ‘datasets’ that were used to aggregate measures of body size.
Metadata refer to our naming scheme employed in our workflow; citation is a descriptor of either the paper citation or dataset citation or a descriptor of manual data aggregated by us; URL is the potential URL if applicable, and number of data points is the number of potential data points that could be used for the analysis.
- https://cdn.elifesciences.org/articles/109047/elife-109047-fig3-data1-v1.zip
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Figure 3—source data 2
A final dataset for potential analysis and modeling, including a total of 94,087 observations (unique combination of species urban affinity values, subrealm, and body size measure) of 20,957 species that had at least one measure of urban affinity and at least one measure of body size.
Note, however, that not every body size measure is made available due to a lack of permissions to share some datasets.
- https://cdn.elifesciences.org/articles/109047/elife-109047-fig3-data2-v1.zip
Figure 3—figure supplement 1
A summary of the number of species, shown per class, gained through taxonomic harmonization, and therefore included in the analysis dataset.
Figure 3—figure supplement 2
The number of taxa, on a log10-transformed scale.
These can be found in Figure 3—source data 2.
Figure 3—figure supplement 3
We chose to model each taxonomic group (i.e. family, order, class, phylum, and kingdom) independently of one another to avoid the influence of where individual families could have no effect but result in a positive effect if modeled jointly.
The top panel shows simulated raw data for two families; the middle panel shows the posterior distribution of a Bayesian model fit for each of these families separately; the bottom panel shows the posterior distribution of a Bayesian model fit for a model including family as a random effect and for a model not including family as a random effect.
Figure 3—figure supplement 4
Supporting analysis showing the influence of different metadata inclusion in model decisions.
An illustrative example showing the influence of using a random slope for body size, by showing the (A) interaction between body size (scaled and log10 transformed) and body size measurement type (metadata; see Methods for details) for the family Accipitridae. Facets represent different types of body size metrics used in the dataset, labeled with a letter identifier and corresponding sample size (n). Lines represent predicted urban affinity based on body size, with 95% credible intervals shown as shaded ribbons. These are extracted from a model fit with an interaction between metadata and body size to purposefully investigate the influence of metadata and the relationship with body size. (B) Posterior distributions of the slope for body size (scaled and log10 transformed) under two model structures: V1 includes a random slope for body size by subrealm and a random intercept for metadata (as presented in main results), while V2 adds a random slope for body size by metadata. The inclusion of this additional random slope in V2 increases uncertainty and pulls slope estimates toward zero, particularly when data are sparse within body size measurement types as illustrated here. Also see Figure 3—figure supplement 5.
Figure 3—figure supplement 5
Supporting analysis showing the treatment of metadata in models.
An illustrative example showing the influence of using a random slope for body size, by showing the (A) Interaction between body size (scaled and log10 transformed) and body size measurement type (metadata; see Methods for details) for the family Apidae. Facets represent different types of body size metrics used in the dataset, labeled with a letter identifier and corresponding sample size (n). Lines represent predicted urban affinity based on body size, with 95% credible intervals shown as shaded ribbons. These are extracted from a model fit with an interaction between metadata and body size to purposefully investigate the influence of metadata and the relationship with body size. (B) Posterior distributions of the slope for body size (scaled and log10 transformed) under two model structures: V1 includes a random slope for body size by subrealm and a random intercept for metadata (as presented in main results), while V2 adds a random slope for body size by metadata. The inclusion of this additional random slope in V2 increases uncertainty and pulls slope estimates toward zero, particularly when data are sparse within body size measurement types as illustrated here. Also see Figure 3—figure supplement 4.
Tables
Appendix 2—table 1
A list of 41 potential ‘types’ of body size that were used for potential inclusion in our body size dataset.
We aimed to incorporate as many types of body size measures as possible and were not restrictive in our searching for body size measures.
| Type of body size | |||
|---|---|---|---|
| Weber’s length | Abdominal length | Biovolume | Body length |
| Body mass | Body mass female only | Carapace width | Cephalothorax width |
| Colony height | Column diameter | Coral diameter | Diameter |
| Dorsal mantle length | Dry mass | Elytron length | Femur length |
| Forewing length | Fork length | Head height | Head length |
| Head width | Height | Hind tibia length | Hindwing length |
| Intertegular distance | Longest length | Plant height | Pronotal width |
| Radius | Shell size | Shell volume | Snout vent length |
| Standard length | Thorax length | Thorax width | Total biomass |
| Total length | Wet mass | Width | ing length |
| Wingspan | |||
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Global relationships between body size and urban affinity across more than 30,000 plant and animal species
eLife 14:RP109047.
https://doi.org/10.7554/eLife.109047.3
