Dependence on a human structure influences the extinction of a non-native lizard population after a major environmental change

Human activity causes major changes in natural landscapes via introduction of non-native species, development on natural habitat, and alteration of local weather patterns. These factors contribute to global change and may interact to affect local populations of plants and animals. We studied a viable, non-native lizard population (Anolis sagrei) in southeast Alabama, USA that has depended upon thermal conditions inside a greenhouse nursery during the winter for at least 10 years. Using Capture-Mark-Recapture surveys, we compared population parameters and movement patterns of this introduced A. sagrei population to a native lizard population (Sceloporus undulatus) that also inhabits our study site. The population size of both species fluctuated over time, but that of A. sagrei was considerably larger than S. undulatus. Anolis sagrei was relatively philopatric and confined within the greenhouse and its immediate vicinity, whereas the S. undulatus population extended into the surrounding forest habitat. The thermal landscape within the greenhouse was substantially altered after the roof was removed due to winds from a tropical storm. Indeed, temperatures of all microhabitats commonly used by lizards frequently dropped below the critical thermal minimum for A. sagrei and below freezing during winter. Post-winter surveys revealed that no A. sagrei individuals survived, indicating that the temperature change in the greenhouse resulted in extinction. The native S. undulatus population, however, was still present after winter. Our study provides rare documentation of an extinction of an established introduced population and illustrates the role that human-made structures and natural weather events play in the process of biological invasion.