The invasive coral Oculina patagonica has not been recently introduced to the Mediterranean from the western Atlantic

Background: Effective policies, management, and scientific research programs depend on the correct identification of invasive species as being either native or introduced. However, many species continue to be misidentified. Oculina patagonica, first recorded in the Mediterranean Sea in 1966, is believed to have been introduced in anthropogenic times and expanding in a west to east direction. However, its present identification and status as a recently introduced species remain to be explored. In this study, we used multi-locus genetic data to test whether O. patagonica in the Mediterranean has been recently introduced from the western North Atlantic. Results: We found no genetic or historical demographic evidence to support a recent introduction of O. patagonica from the western North Atlantic or an expansion across the Mediterranean. Instead, Mediterranean and Atlantic populations are genetically distinct and appear to have begun diverging about 5 Mya. We also found evidence of a fossil record of Oculina spp. existing in the eastern North Atlantic millions of years before the present. Conclusions: Our results suggest that Mediterranean populations of O. patagonica have long been isolated from the western Atlantic, either in undetectable numbers or overlooked and undersampled sites and habitats, and have only recently been expanding to invasive levels as a result of environmental changes. Accurate identification of species' invasive statuses will enable more effective research programs aimed at better understanding the mechanisms promoting the invasive nature of species, which can then lead to the implementation of efficient management plans.