Increase in knowledge of the marine gastropod fauna of Lebanon since the 19th century

We hereby review and update the current state of knowledge on the Lebanese gastropod biota based on published literature and the study of new samples. Review of 1543 published records yielded 237 gastropod taxa. New samples from the Lebanese coast yielded 2414 living specimens and 4003 empty shells, belonging to 188 taxa. Forty-six of the taxa are new records for the Lebanese fauna, bringing the gastropods known from Lebanon to 283 species. Literature records also included 71 nominal gastropod taxa based on type material from Lebanon, including 3 genera, 8 species, and 60 subspecific units. Of these, only 13 are retained as available. Of the 283 gastropod taxa known from Lebanon, 41 are aliens and 7 are cryptogenic. The majority of nonnative taxa were recorded only during the last decades, particularly from 1980 to 2019. Results from the present study question the common assumption that this region has extremely low native diversity. The flora and fauna of the Lebanese coast remain relatively unexplored and our data support the perception that several formerly abundant species have recently collapsed. Despite these advances, the lack of scientific data on biodiversity and community structure of Lebanese habitats and geographic zones is likely to hamper conservation actions and legal protection of critical species. We therefore recommend additional field and laboratory research to increase knowledge of both taxonomic composition and species' distributions in Lebanon and elsewhere in the easternmost Mediterranean Sea.