Phylogeography of the Atlantic Blue Crab Callinectes sapidus (Brachyura: Portunidae) in the Americas versus the Mediterranean Sea: Determining Origins and Genetic Connectivity of a Large-Scale Invasion

Due to its large size and importance in commercial and recreational fishery, the blue crab, Callinectes sapidus, has always been a well-known crab species all along the temperate and tropical American east coast. Over the past century, there have been increasing reports of this species from Africa, Asia, and Europe. However, the corresponding introduction pathways remain Citation: Schubart, C.D.; Deli, T.; Mancinelli, G.; Cilenti, L.; Gil Fernández, A.; Falco, S.; Berger, S. Phylogeography of the Atlantic Blue Crab Callinectes sapidus (Brachyura: Portunidae) in the Americas versus the Mediterranean Sea: Determining Origins and Genetic Connectivity of a Large-Scale Invasion. Biology 2023, 12, 35. https://doi.org/10.3390/ biology12010035 Academic Editors: Dario Capizzi, Sandro Bertolino and Tim Adriaens Received: 18 November 2022 Revised: 14 December 2022 Accepted: 20 December 2022 Published: 24 December 2022 Copyright: © 2022 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). a reason for speculation. Its long larval development in marine plankton and tolerance towards varying salinities are prerequisites for a successful dispersal by marine currents or in ballast waters. Onthe other hand, being a highly valued seafood, it is conceivable that C. sapidus may have been intentionally released to establish breeding populations elsewhere. The species started expanding conspicuously in the east Mediterranean after the 1930s (Nile Delta, Thessaloniki Bay). On the other hand, western Mediterranean records are much more recent and regionally confined. The reconstruction of their origin is the main goal of the current study. For that purpose, the genetic composition of populations from the American native range and from the entire Mediterranean needed to be included and used for the overall comparison. It appears that only a few founding individuals are responsible for the invasion into Spanish and Italian waters, arguing in favor of a dispersal theory.