Use of human-made structures facilitates persistence of a non-native ectotherm

Abstract

Human-modified habitats often harbor non-native populations and may facilitate the transport and establishment of invasive species. Disturbed areas are typically warmer than adjacent natural habitats (e.g. urban heat island effect), and thus, ectotherms may benefit from landscape modifications. Although much research has considered how urban areas facilitate invasion, greenhouses may enhance successful invasion to rural areas via transport of exotics through plant shipments and increased temperatures. However, for non-native species to establish and become invasive, populations must adapt to the local climate outside the protection of greenhouses. We studied a population of non-native lizards (Anolis sagrei) that have been naturalized for at least 10 years in a greenhouse in Opelika, Alabama, USA, which is far above the northernmost point of the species’ continuous invasive range. The greenhouse was warmer than adjacent outdoor habitat at all hours of the day and often reached temperatures above the critical thermal maximum of lizards. Our measurements of behavior and thermal physiology suggest that lizards have not physiologically adapted to these novel conditions, but rather, behavioral modifications likely allow the population to persist. Moreover, we found no evidence that lizards are dispersing from the greenhouse, and we conclude that this population is dependent on this structure for survival. While human structures and human-modified habitats may facilitate the transport of non-natives, these environments potentially shield populations from selective pressures necessary for species to spread throughout non-native areas. This may contribute to a long lag phase which characterizes many invasions.