Ecological overlap and divergence in natural and urbanized habitats in two species of sympatric anoles

Abstract

The habitat of organisms can have a significant impact on an animal's fitness, and the ability of animals to choose suitable habitats may change with human induced global change. Urbanization in particular has had drastic effects on natural habitats including changes to the physical environment and introduction of nonnative species. Ectotherms are particularly affected by environmental changes which can impact their ability to regulate their body temperature. In this study, we compared habitat preference and the effects of habitat structure in urban and natural environments on thermal preference and thermoregulation in two species of introduced ectotherms, the brown anole, Anolis sagrei, and the bark anole, Anolis distichus. We found evidence of species- and sex-specific differences in habitat use and thermal biology related to environment (i.e. natural vs urban). The urban environment had a higher temperature and fewer available perches than the natural environment. Brown anoles were better at maintaining their preferred body temperature than bark anoles. Bark anoles occupied higher perches than brown anoles, and brown anoles exhibited a greater magnitude of sexual dimorphism in their size, habitat use, and thermal biology. The lower temperature and increased habitat space in natural environments suggests these environments are at risk of invasion by nonnative species as global warming continues, and the superior ability of brown anoles to persist and maintain their body temperatures between habitats may be a reason for their success as an invasive species across the globe.

Keywords: Anolis distichus; Anolis sagrei; Bark anole; Brown anole; Invasive species; Panting threshold; Thermal limits; Thermal regulation; Urbanization.