Community science records reveal a new population of the nudibranch <i>Dendrodoris limbata</i> (Cuvier, 1804) outside its native distribution range

ABSTRACT Allochthonous species are one of the most important reasons for local biodiversity loss. Although colonization of new habitats has been associated mainly with vagile species, low-dispersive species have earned this capability aided by human-related activities. Additionally, in the context of climate change, species can colonize habitats that in normal conditions they would not be able to do so. Thus, it is of great interest to understand the dispersal of non-native species into new habitats and identify their colonization routes. Here, by validating community science records uploaded to public web pages starting in 1996, we confirm the presence of Dendrodoris limbata, a low-dispersive endemic species from the Mediterranean Sea, in the Atlantic Ocean. Our data indicates that this species has drastically increased its population size in Brittany, France and now sporadically appears in Galicia in NW Spain. Molecular samples from Galicia allowed us to infer the potential population source leading to the colonization of that population. Moreover, we tracked surface and deep temperature trends in six regions across the current distribution of the species starting from 1993, considering both native and non-native parts of the range, and found evidence that the increase in the temperature of the Atlantic Ocean could be compatible with preindustrial Mediterranean Sea conditions. Overall, our results indicate that Brittany and Galicia could act as potential thermal shelters for Dendrodoris limbata. This study raises awareness on the Brittany and Galician shores, since other Mediterranean species could also find a thermal shelter in these regions, allowing subsequent introductions in the next decades.