Big City Living: A Global Meta-Analysis Reveals Positive Impact of Urbanization on Body Size in Lizards

Abstract

Urban environments pose different selective pressures than natural ones, leading to changes in animal behavior, physiology, and morphology. Understanding how animals respond to urbanization could inform the management of urban habitats. Non-avian reptiles have important roles in ecosystems worldwide, yet their responses to urbanization have not been as comprehensively studied as those of mammals and birds. However, unlike mammals and birds, most reptiles cannot easily move away from disturbances, making the selective pressure to adapt to urban environments especially strong. In recent years, there has been a surge in research on the responses of lizards to urbanization, yet no formal synthesis has determined what makes an urban lizard, in other words, which phenotypic traits are most likely to change with urbanization and in which direction? Here, we present a qualitative synthesis of the literature and a quantitative phylogenetic meta-analysis comparing phenotypic traits between urban and non-urban lizard populations. The most robust finding from our analysis is that urban lizards are larger than their non-urban counterparts. This result remained consistent between sexes and taxonomic groups. Hence, lizards that pass through the urban filter have access to better resources, more time for foraging, and/or there is selection on attaining a larger body size. Other results included an increase in the diameters of perches used and longer limb and digit lengths, although this may be a result of increased body size. Urban lizards were not bolder, more active or exploratory, and did not differ in immune responses than non-urban populations. Overall, studies are biased to a few geographic regions and taxa. More than 70% of all data came from three species of anoles in the family Dactyloidae, making it difficult to generalize patterns to other clades. Thus, more studies are needed across multiple taxa and habitats to produce meaningful predictions that could help inform conservation and management of urban ecological communities.

Growing up in a new world: trait divergence between rural, urban, and invasive populations of an amphibian urban invader

“…Given the substantial literature reporting differences in tadpole growth rates due to ecological or evolutionary factors, we were surprised that we did not find any differences in growth rate among the three location types. Several studies on body size differences among rural and urban, as well as among native and invasive populations, across a wide range of taxa report higher growth rates and larger adult body sizes for urban and/or invasive populations (Phillips 2009;y Gomez and Van Dyck 2012;Sargent and Lodge 2014;Hall and Warner 2017;Iglesias-Carrasco et al 2017;Pujol-Buxó et al 2020;Putman and Tippie 2020), which is widely attributed to lower interspecific competition, higher food abundance, and novel ecological opportunities in urban and/ or invasive ranges. The opposite trend is, however, also possible.…”

Selection in the city: Rapid and fine‐scale evolution of urban eastern water dragons

“…Additionally, these two traits may diverge between our city parks as dragons adapt to locally available food types or are constrained in their growth by the local resource availability. Snout-vent length and jaw width are known to associate with diet and resource access in lizards (Herrel et al 2001;Putman and Tippie 2020) and resource density may be increased through the availability of human rubbish (Gross 2015) and/or relaxed predation, which drives longer foraging times (Eötvös et al 2018). As these factors likely vary within a single metropolis, we can hypothesize that they could drive the phenotypic divergence observed between these city dragon populations.…”

The interplay of spatial scale and landscape transformation moderates the abundance and intraspecific variation in the ecomorphological traits of a phyllostomid bat

“…That is, human environments might promote directional selection processes that alter the ecomorphological traits of the species (e.g., Puckett et al 2020). This pattern has been increasingly documented in several vertebrates such as lizards (Lazić et al 2013, Hall & Warner 2017, Putman & Tippie 2020), small non-volant mammals (Snell-Rood & Wick 2013, Puckett et al 2020), bats (Tomassini et al 2014), birds (Liker et al 2008, Caizergues et al 2021), and middle-sized carnivores (Parsons et al 2020). Nevertheless, most studies focused on comparing populations between discrete categories of land-use intensification, e.g., urban vs. rural, ignoring the role of landscape emergent properties and the spatial scales that better correlate with phenotypic changes of fauna in human environments (Strubbe et al 2020).…”