Eastern spread of the invasive Artemia franciscana in the Mediterranean Basin, with the first record from the Balkan Peninsula.
In the last 30 years since its first appearance in Portugal, the North-American Artemia franciscana has successfully invaded hypersaline habitats in several Mediterranean countries. Here, we review its spread in the Mediterranean Basin since its first occurrence in the 1980s and report its first occurrence in Croatia, based on both morphological identification (adults) and genetic evidence (cysts). The haplotypes we found in the population from this new locality (two of which were new to both the native and invaded ranges of A. franciscana) suggest either direct or secondary introduction from the main harvested cyst sources (Great Salt Lake or San Francisco Bay, USA) and indicate that some genetic native diversity in the species has not yet been captured by existing studies. Our finding means that the species has reached the eastern shores of the Adriatic Sea and therefore is now present on the Balkan Peninsula. We detected that its eastward spread is still continuing, posing a fundamental threat to remaining populations of native Artemia species in Eastern Europe, which highlights the need for preventive measures.