Abstract
<title>Abstract</title> <p> Understanding connectivity is essential for biodiversity conservation and fisheries management as most marine species depend on larval dispersal for population persistence and recolonisation. This study investigates the genetic structure and population connectivity of the gooseneck barnacle ( <italic>Pollicipes pollicipes</italic> ), a commercially exploited species found along the north-east Atlantic coast from Senegal to Brittany. The study combines genetic analyses using microsatellite loci with biophysical larval dispersal modelling to assess connectivity at the species' range and regional levels. The results reveal clear genetic differentiation between African and European populations, possibly due to an oceanographic barrier at the Strait of Gibraltar. In contrast, although European populations were regionally differentiated, they were less different from Portugal to Brittany than from Africa. This supports the hypothesis of post-glacial northward recolonisation from a single Iberian refuge, followed by ongoing but chaotic larval exchanges along the Atlantic coast. At a finer regional scale, Brittany populations function as a two-source metapopulation model, supplying larvae to neighbouring areas depending on coastal currents directions. Further assignment tests and hydrodynamic simulations suggest that Breton populations occasionally receive larvae from Iberian regions, particularly in late summer, when oceanic currents and prolonged larval duration may favour long-distance dispersal along the French coastlines. Although these events are infrequent, they appear to be sufficient to maintain some genetic continuity between Iberian and French populations. These results have significant implications for the management of sustainable fisheries, emphasising the importance of protecting key source populations and incorporating genetic and oceanographic data into marine spatial planning and conservation strategies. </p>