Contrasting effects of climate change on the European and global potential distributions of two Mediterranean helicoid terrestrial gastropods

Predicting the impacts of global climate change on the current and future distribution of alien or endangered species is an essential subject in macroecological studies. Although several investigations have been devoted to animal and plant species, few have addressed terrestrial gastropods. We employed spatial distribution modelling to construct European and global potential distribution ranges of two land snails (Cernuella virgata and Hygromia cinctella) using current and future climate scenarios. Both species have been continuously spreading northward from the Mediterranean region, also being introduced to a few areas outside Europe. We found that under the current climate scenario, most presently occupied areas in Europe are also at high probability of future occurrence of these species. However, under four future climatic conditions, these snails will undergo contrasting scenarios. C. virgata will have a large potential gain, likely due to rising temperatures and its weak fluctuations. In this species, global warming increases in potential area size, accompanied by its morphological and physiological adaptations to arid conditions and the ability to passively disperse, are likely to facilitate invasion into new regions of the world. In contrast, there is no significant change in the geographical distribution of colonisation-prone areas for H. cinctella. Our results demonstrate that wetter climatic conditions in the driest season and greater temperature variability will be key limiting factors of its distribution in the future. An understanding of colonisation patterns can help to better manage these invaders and also to formulate policies for their control.