Where is the genus Elysia in the western Atlantic? Potential distribution, species richness and representation in marine protected areas

The western Atlantic Ocean is one of the areas with the largest species richness of sea slugs in the genus Elysia (30 out of the 101 species described have been reported in this region). Nevertheless, the lack of knowledge on many of these species hinders efforts to estimate regional richness and identify the factors affecting their distribution. We used the maximum entropy algorithm Maxent to develop ecological niche models for 14 species of Elysia in the western Atlantic Ocean. These models were meant to show the potential distribution of the genus and identify locations with the highest richness. Input data used to build niche models were presence records (obtained from several sources) and bioclimatic and geophysical variables from the Bio-ORACLE and MARSPEC platforms. Species with less than seven records were considered for the calculation of richness, but not for modelling. Results show low habitat suitability for the species modelled here at the mouth of rivers and in hypoxic zones and low-temperature areas. The two variables that best explained species distribution patterns were the distance to shore and the maximum monthly temperature. From the total area with adequate environmental conditions for the genus, only 20.3% is located within marine areas under some protection category.