New Kid in Town: Pinna rudis spreads in the eastern Mediterranean.

In the Mediterranean Sea, the genus Pinna encompasses two large fan-shaped bivalve species, Pinna nobilis and Pinna rudis. Historically, both species coexisted in the western Mediterranean until a Mass Mortality Event brought P. nobilis to the brink of extinction. Notably, P. rudis remained unaffected by the MME, and its recent successful recruitment and further spread has been hypothesized to be linked to the local extinction of P. nobilis. Although P. rudis has been sparsely recorded in the eastern Mediterranean Sea (but with some of these records being doubtful), reports emerging in the summer of 2023 from researchers and citizens have unveiled its sudden spread in Greece. This study presents an updated review of the distribution of P. rudis in the Mediterranean Sea, integrating data from literature and online repositories. Additionally, the recent presence of the species within Greek waters was documented through a dedicated survey and molecularly confirmed through two distinct molecular methods. For the distribution mapping of P. rudis in Greece, we also included information derived from a citizen science initiative, following photo-identification of the species. Consequently, this research confirms the recent spread of P. rudis in South Crete and the Greek Ionian Sea (first verified records of the species in both regions), in marine areas where P. nobilis has become extinct, further strengthening the hypothesis that P. rudis has benefited from the collapse of P. nobilis populations