Body size and reproduction of a non-native lizard are enhanced in an urban environment

Abstract

Growth and body size are influenced by the environment and each have consequences for reproduction and, thus, fitness. Anthropogenically altered habitats (i.e. cities) create novel conditions that may enhance or reduce fitness via environmentally induced changes in growth or body size. By comparing urban and natural habitats, we can quantify the effects of human-modified landscapes on fauna and increase our general understanding of responses to novel environments. We collected lizards, Anolis cristatellus (Duméril & Bibron, 1837), from adjacent urban and forested areas, bred them in the lab under common conditions, measured body size, latency of oviposition, fecundity and egg size for each female and measured growth of hatchlings over 3 months. Female lizards from the city were larger, had a greater body condition index at the beginning of the breeding season and started laying eggs sooner than those from the forest, which increased their fecundity. Females from the forest, but not the city, improved their body condition during the study, so we infer that urban environments maximize body condition of anoles. Moreover, hatchlings from urban mothers had higher growth rates than those from the forest suggesting that body size differences may be due to intrinsic factors. Thus, we conclude that urban environments can enhance growth and reproduction in some vertebrate ectotherms.