Patterns and causes of population subdivision in the marine environment

An accurate assessment of population genetic subdivision is crucial in making informed decisions for the management and conservation of marine resources. However, obtaining a precise assessment is particularly challenging since population subdivision results from the interaction of many biological and environmental variables. Here, the patterns of population subdivision that can be attributable to gene flow in 8 marine fish species from 11 different locations in the Mediterranean Sea and the Eastern Atlantic Ocean are analysed. The species considered are Mullus barbatus, Mullus surmuletus, Tripterygion delaisi, Apogon imberbis, Symphodus tinca, Diplodus vulgaris, Serranus cabrilla and Oblada melanura. These species differ significantly in their dispersal capabilities as presumed by their diverse early-life stage characteristics, and were sampled over multiple habitats at two geographical scales. A total of 1640 individuals (mean 168/species) were surveyed at 63 species-specific and 10 cross-amplified microsatellite loci (mean 9.1/species). The overall results show that genetic structure patterns cannot be predicted confidently by the presumed dispersal capabilities of the species. Species such as S.tinca, M.barbatus and O.melanura, showed highly incongruent population structuring patterns to those expected. Furthermore, the results also suggest that species with extreme variations between their life history traits such as D.vulgaris and A.imberbis, can display similar patterns of genetic structuring in the presence of common oceanographic variables, whereas species with slight differences such as M.barbatus and M.surmuletus can display contrasting patterns of genetic partitioning. These results highlight the importance understanding the role of environmental features and life history traits in establishing ecologically meaningful connections among marine fish species. Furthermore, this study provides evidence of the usefulness of multi-species approaches in planning to incorporate population genetic information into conservation and management of marine fish resources