On the path to extinction: Helix godetiana Kobelt, 1878, the only threatened Helix species in Greece

Land snails and the Aegean Archipelago offer an intriguing combination for studying biodiversity, biogeography and ecology. A region with high environmental and temporal heterogeneity and a tri-continental biotic influence and a group of organisms with low active dispersal abilities, high endemism, as well as the particularity to leave shells as traces of past presence, set an ideal stage for testing biodiversity patterns and exploring multisource threats, especially in the era of the ongoing biodiversity crisis. In this study, we examine Helix godetiana , a large-sized, threatened and endemic land snail of the central and south Aegean Islands. The species has been extirpated from 22 of the 32 islands where it was historically present. We identify potential drivers of its extinction, as Helix godetiana faces several threats across its current range, including competitive exclusion by Cornu aspersum , a species with continuing expansion in the Aegean and climate change disrupting its unusual breeding cycle, which occurs in late spring. Our findings shed light on potentially major, yet previously unexplored, threats on endemic molluscs of the Aegean Islands, a European biodiversity hotspot.