The perils of city life: patterns of injury and fluctuating asymmetry in urban lizards

Abstract

Animals that live in cities face a number of challenges particular to the urban environment that may impact on overall health and survival. Nevertheless, relatively few studies have investigated injury and health in urban species. We measured body condition, injury rate and fluctuating asymmetry in urban and forest populations of the tropical lizard Anolis cristatellus. We found that although there were strong differences in body condition between urban and forest populations, the direction of this difference varied between municipalities. We also found that injury rates (amputated digits and bone fractures) were slightly, but significantly, more common in urban populations; this phenomenon may be due to changes in intraspecific interactions or predation pressure in urban sites. Contrary to our expectations, we found that fluctuating asymmetry was greater in forest compared to urban populations. Because our data were collected from adults, this may be a sign of stronger natural selection on the symmetry of functional traits in urban than in forest environments. Finally, we found no persuasive evidence that city living is inherently detrimental to individuals of this species despite a slightly higher rate of injury. Being able to overcome the challenges of city life may be integral to urban persistence and a step along the path to urban adaptation.

Superfrogs in the city: 150 year impact of urbanization and agriculture on the European Common Frog

“…These findings suggest that habitat quality improved compared with prewar conditions and environmental stress as well as nitrogen pollution decreased in Berlin, despite increasing housing construction and densification of urban infrastructures after war with a construction peak in 1997 (Jefferson & Russel, 2008;Keinath et al, 2020;Lazić et al, 2013;Merckx et al, 2018 to very urban (i.e., densely built-up areas with dense road network), but as well to barely urbanized areas (i.e., sites characterized by arable land, forest or grassland, which should not be confused with developed urban greenspace). Although seemingly counterintuitive, these findings are in accordance with other studies, which reported larger body sizes and lower levels of CFA in urban areas, compared to natural habitats for amphibians and reptiles (French et al, 2018;Hall & Warner, 2017;Iglesias-Carrasco et al, 2017;Winchell et al, 2019).…”

“…Largest individuals originated from areas with moderate degree of impervious surfaces (>35% < 70%), implying that R. temporaria actually encountered more favorable environmental conditions in habitats with intermediate urbanization degrees compared to very urban (i.e., densely built-up areas with dense road network), but as well to barely urbanized areas (i.e., sites characterized by arable land, forest or grassland, which should not be confused with developed urban greenspace). Although seemingly counterintuitive, these findings are in accordance with other studies, which reported larger body sizes and lower levels of CFA in urban areas, compared to natural habitats for amphibians and reptiles (French et al, 2018;Hall & Warner, 2017;Iglesias-Carrasco et al, 2017;Winchell et al, 2019).…”

Morphological Stability of Rural Populations Confirms Their Use As Controls in Urban Ecology Studies

“…For example, in carabid beetles, FA increased with urbanisation in species considered to be negatively affected by urbanisation, whereas such a relationship was not found in species that are more tolerant to urbanisation (Weller & Ganzhorn 2004); however, in another study FA did not change along rural-urban gradients (Elek et al 2014). Similarly, different studies in lizards have reported an increase in FA in response to urbanisation (Lazić et al 2013), no changes in FA in response to urbanisation (Sacchi et al 2018), and even a decrease in FA in response to urbanisation, the authors interpreting this last result as natural selection being stronger in urban populations and asymmetrical individuals being less likely to survive to adulthood (Winchell et al 2019).…”

It’s Not Easy Being Green: Behavior, Morphology, and Population Structure in Urban and Natural Populations of Green Anole (Anolis carolinensis) Lizards

“…This complexity appears to extend to other Anolis species as well; for example, Hall and Warner (2017) found the opposite pattern in A. cristatellus lizards in south Florida, with A. cristatellus from an urban site exhibiting higher body condition than those from a forested site, yet Chejanovski et al (2017) found no effect at all of urbanization on body condition in A. cristatellus within their native range in Puerto Rico, but did find higher condition in urban A. sagrei lizards compared to those from natural populations. Finally, Winchell et al (2019) found that body condition does vary between urban and natural populations of A. cristatellus in Puerto Rico, albeit not always in a consistent direction. The mechanisms underlying these changes in condition are unclear, and it is worth noting that morphological condition indices have often been criticized, and that their functional and ecological relevance is controversial (Vervust et al, 2008; but see Husak and Lailvaux, 2019).…”