The spreading of the invasive Italian wall lizard on vulcano, the last Island inhabited by the critically endangered Aeolian wall lizard

Abstract

The Aeolian Wall Lizard (Podarcis raffoneae) is an endemic species of the Aeolian Archipelago of Italy (Mediterranean Sea). Its distribution is limited to three islets and two relict populations on a relatively large island: Vulcano (a population on the summit of Gran Cratere volcano and another on Capo Grosso promontory). The critically endangered Aeolian Wall Lizard is threatened by the introduction of the Italian Wall Lizard (Podarcis siculus), which successfully competes and hybridizes with the endemic lizard. The invasive lizard is widespread on Vulcano, although the literature does not provide the exact distribution. Our first aim was updating the distribution of the Italian Wall Lizard on Vulcano, with special attention to the last enclaves of the Aeolian Wall Lizard. Our second purpose was investigating the factors determining this distribution range. In the spring of 2016, we surveyed the Italian Wall Lizard distribution on Vulcano, considering 10 human-related and 10 natural areas, including Gran Cratere volcano and Capo Grosso promontory. We recorded the presence of the invasive Italian Wall Lizard in each survey area. As a consequence, the Aeolian Wall Lizard populations of Vulcano face an imminent extinction risk. The main factors increasing the presence probability of this invasive lizard on Vulcano were the nearness to the harbor (the introduction gateway) and the urbanization degree (the invasion pathway). Therefore, we suggest the implementation of a control plan simultaneously acting on the areas of sympatry (mostly Capo Grosso promontory), the introduction gateway (Vulcano harbor), and the source populations (urban areas).