Abstract
The spread of urban development has dramatically altered natural habitats, modifying community relationships, abiotic factors, and structural features. Animal populations living in these areas must perish, emigrate, or find ways to adjust to a suite of new selective pressures. Those that successfully inhabit the urban environment may make behavioral, physiological, and/or morphological adjustments that represent either evolutionary change and/or phenotypic plasticity. We tested for effects of urbanization on antipredator behavior and associated morphology across an urban-wild gradient in the western fence lizard (Sceloporus occidentalis) in two California counties, Santa Barbara and San Luis Obispo. We compared college campuses in both counties with adjacent rural habitats, conducting field trials that allowed us to characterize antipredator behavior in response to the acute stress of capture. We found notable divergence between campus and rural behavior, with campus lizards more frequently exhibiting diminished escape behavior, including tonic immobility, and lower sprint speeds. Furthermore, campus females had significantly shorter limbs, and while this did not explain variation in sprint speed, those with shorter limbs were more likely to show tonic immobility. We hypothesize that these parallel behavioral and morphological changes on both campuses reflect adjustment to a novel environment involving changes in predation and human presence.
Highlights
Across the globe, human-induced environmental change is having profound impacts on other species, through habitat loss and alteration, spread of invasive species, pollutants, and climate change [1,2,3,4,5,6]
Our study focused on urban and rural fence lizards from two replicate populations in Santa Barbara and San Luis Obispo counties
We found compelling evidence of parallel differentiation in behavior and morphology between campus and rural fence lizards in Santa Barbara and San Luis Obispo, California
Summary
Human-induced environmental change is having profound impacts on other species, through habitat loss and alteration, spread of invasive species, pollutants, and climate change [1,2,3,4,5,6]. In anthropogenically-altered habitats, species may experience changes in key biotic factors, such as predators, parasites, competitors, and prey, as well as changes in abiotic factors, such as temperature, noise, traffic, and substrate type[7,8,9]. Recent work has shown diverse adjustments in physiology, behavior, and even morphology in urban habitats. Some urban species have been shown to have altered stress physiology and immune function [16,17]. There is evidence of alterations in bill size in house finches, limb length in Anolis lizards, and wing length in cliff swallows associated with colonization of urban areas [19,20,21]
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