| Summary: | Species persist over time, due to exchange of individuals between subpopulations. In the marine environment, most benthic organisms have complex life cycles including pelagic larvae that are transported by ocean currents promoting species dispersal. Larval dispersal connects geographically distant populations and determines population structure. The knowledge about this biologic process provides relevant information for conservation of marine populations. This study investigates the genetic structure and connectivity of deep-sea mussel populations between fragmented habitats in the NE Atlantic and Mediterranean. The mitochondrial Cytochrome Oxidase I (mtCOI) gene was used to analyze site-specific genetic diversity and the population structure of two mussel species, Idas modiolaeformis and “Idas” simpsoni. Populations of each species are not geographically isolated. The presence of one dominant haplotype for each species suggests shared ancestral polymorphisms between Mediterranean and NE Atlantic populations. The overall high genetic differentiation observed in I. modiolaeformis indicates that the metapopulation is structured. Distant populations, located in Atlantic and E Mediterranean, revealed low genetic distances, suggesting gene flow between the two regions. Genetic and geographical distances support an island model of I. modiolaeformis population structure. A major drawback of this study is concerned with the discrepant number of individuals among populations. Further research will be needed, using more specimens and other gene markers, to investigate connectivity patterns at different spatial scales.
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