Assessing the context‐dependence of invasiveness in the Italian wall lizard (Podarcis siculus) )

The number of alien species has increased significantly in recent decades, but only a few become invasive, posing threats to biodiversity and human activities. However, the invasive potential of alien species might depend on environmental compatibility and local conditions. The Italian wall lizard (Podarcis siculus) has been introduced across Europe, North Africa, and North America, and its actual invasiveness varies by location. Detrimental impacts have been observed mainly on congeneric species, often due to competition or habitat overlap. Nevertheless, in some regions, including the United States, no evidence for spread and impact has been reported. On Gorgona Island, Italy, the Italian wall lizard was likely introduced accidentally around 2000 and has rapidly expanded. This study examined the colonization of the Italian wall lizard on Gorgona Island and its interaction with the native common wall lizard (P. muralis). Findings indicate the Italian wall lizard thrives in human-altered habitats, while the common wall lizard persists in natural areas. The spread of the Italian wall lizard appears to be driven by environmental conditions rather than inherent aggressiveness, aligning with patterns observed on other Mediterranean islands. Its expansion stalled between 2021 and 2024, suggesting habitat saturation, not competition, limits spread. The study warns against labeling the Italian wall lizard as uniformly invasive, advocating context-specific assessments to avoid misdirecting conservation resources.