1. Pinna nobilis is an endemic bivalve of the Mediterranean Sea, and a vulnerable species registered as endangered and protected under the European Council Directive 92/43/EEC and Barcelona Convention. 2. In early autumn 2016, a mass mortality event impacted P. nobilis populations in the south-western Mediterranean Sea, including the Balearic Islands. At the time of this study, P. nobilis still maintained high population densities along the Balearic coasts (Western Mediterranean).3. This study evaluated the connectivity of P. nobilis post-larvae and adults in seagrass habitats around the Balearic Islands and identified its source and sink populations.These objectives were reached through a multidisciplinary approach including population genetics (10 microsatellites) and hydrodynamic modelling. 4. High genetic diversity was found and significant genetic differentiation (inferred by fixation index F ST ) was detected between post-larvae samples, but not between adult populations. Significant genic and genotypic differentiation was recorded for adults and post-larvae.5. This pattern was confirmed by correspondence analysis using allele frequencies.The genetic connectivity pattern was consistent with marine currents and dispersal models.6. This work not only improves knowledge of the P. nobilis gene pool in south-west Mediterranean populations and their connectivity patterns, but is also crucial to help evaluate the possibility of recovery from source populations and the possibility of restocking programmes, as well as provide a solid base to establish effective marine reserve networks.

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The red algal genus Porphyra is sister to the genus Pyropia, the single most valuable marine crop in the Orient. We developed microsatellite loci for the red alga Porphyra umbilicalis, a widespread species in the Northern Atlantic. Enriched DNA libraries were constructed and 68 loci were screened for amplification and polymorphism. Seven polymorphic microsatellite markers were isolated using 44 individuals collected from four natural populations. The number of alleles per locus ranged from two to 12. Null alleles were detected in three loci. Among the markers reported, we tested also cross-amplification with two other Porphyra spp. These polymorphic microsatellite markers should be useful for investigating population genetic structure of P. umbilicalis in the North East Atlantic.