Do urban habitats induce physiological changes in Mediterranean lizards?

Urban environments offer dramatically different habitats for wildlife compared with natural environments. They provide, for example, different levels of resource availability, anthropogenic night light, and microclimates (e.g., urban heat islands). For reptiles, increased temperatures in the city can lead to increased energetic demands and metabolic rates unless they change their morphology and physiology and adapt or acclimatize to the urban conditions. We explored differences in metabolic rate, evaporative water loss, and body size of two lizard species - rock agamas (Laudakia vulgaris) and Mediterranean house geckos (Hemidactylus turcicus), from urban habitats and nearby natural open areas. When tested in the lab, we expected to identify physiological adaptations resulting in decreased metabolism in urban individuals. Both species had similar body lengths and masses at both habitat types, suggesting any differences in costs and benefits between urban and natural environments do not affect their overall size or body condition. In the laboratory, metabolic rates were similar in individuals from both habitats for both species, indicating no long-term adaptations in this trait. However, urban geckos (but not agamas) had higher evaporative water loss than conspecifics from more natural habitats. This may suggest different compositions of epidermal lipids affecting the gecko skin's resistance to evaporation between the habitats. Overall, our results highlight different elements of the urban environment that might affect reptiles. However, the differences between species urge caution in interpreting the results to other species and locations. With increasing urbanization worldwide, understanding when and to what degree local adaptations can occur can help us predict reptile species distribution and survival in light of future anthropogenic changes.