Unravelling the role of oceanographic connectivity in intra-specific diversity of marine forests at global scale

AimIntra-specific diversity results from complex interactions of intermingled eco-evolutionary processes along species history, but their relative contribution has not been addressed at the global scale. Here, we unravel the role of present-day oceanographic connectivity in explaining the genetic differentiation of marine forests across the ocean. LocationGlobal. Time periodContemporary. Major taxa studiedMarine forests of brown macroalgae (order Fucales, Ishigeales, Laminariales, Tilopteridale). MethodsThrough systematic literature revision, we compiled a comprehensive dataset of genetic differentiation, encompassing 662 populations of 34 species. A biophysical model coupled with network analyses estimated multigenerational oceanographic connectivity and centrality across the marine forest global distribution. This approach integrated species dispersive capacity and long-distance dispersal events. Linear mixed models tested the relative contribution of site-specific processes, connectivity, and centrality in explaining genetic differentiation. ResultsWe show that spatiality dependent eco-evolutionary processes, as described by our models, are prominent drivers of genetic differentiation in marine forests (significant models in 92.6 % of the cases with an average R2 of 0.49 {+/-} 0.07). Specifically, we reveal that 19.6 % of variance is explicitly induced by contemporary connectivity and centrality. Moreover, we demonstrate that LDD is key in connecting populations of species distributed across large water masses and continents. Main conclusionsWe deciphered the role of present-day connectivity in observed patterns of genetic differentiation of marine forests. Our findings significantly contribute to the understanding of the drivers of intra-specific diversity on a global scale, with implications for biogeography and evolution. These results can guide well-informed conservation efforts, including the designation of marine protected areas, as well as spatial planning for genetic diversity in aquaculture, which is particularly relevant for sessile ecosystems structuring species such as brown macroalgae.