Abstract
The Moorish gecko Tarentola mauritanica is currently expanding around the Mediterranean basin as a result of natural dispersal and anthropogenic spread. The species is observed at several sites in sympatry with other gecko species. To date, no impact has been observed on the native species and T. mauritanica is not considered invasive. We present an eight-year survey in southern France, where it lives in sympatry with the European leaf-toed gecko Euleptes europaea. The survey started when the Moorish gecko was rare which enabled us to observe an important increase in abundance. This increase was strongly correlated with a notable decline of E. europaea, explaining 49% of transect-specific temporal variation in abundance. We suspect that the increase in T. mauritanica density is causally related to this decline and recommend intensive monitoring of the species throughout the Mediterranean basin to determine whether or not the species should be classified as invasive. Keywords: Euleptes europaea, Tarentola mauritanica, temporal trends, biotic interaction, competition, invasive alien species