Genetic Diversity and Connectivity of Syngnathid Fish in Spanish National Parks: Conservation Insights From Protected Marine Ecosystems

ABSTRACT Spanish National Parks (NPs) are protected areas for biodiversity conservation, including two Maritime–Terrestrian NPs: The Atlantic Islands of Galicia, PNIA (NW Spain) and Archipelago of Cabrera, PNAC (Balearic Islands). This study was aimed to conduct a 3‐year genetic survey of syngnathid fish species (i.e. seahorses and pipefish) identified in both NPs and nearby unprotected areas, using mitochondrial and microsatellite markers. A diversity of species was identified with differential distribution among NPs and adjacent areas studied. Pipefish ( Syngnathus acus , S. abaster , S. typhle , Entelurus aequoreus , Nerophis lumbriciformis , N. maculatus , and N. ophidion ) predominated, while seahorses ( Hippocampus guttulatus ) were much less abundant. Genetic data and phylogenetic analysis clarified in situ morphological identification. Mitochondrial haplotypes for each species clustered into monophyletic groups, supporting the identification of a cryptic lineage of S. abaster in PNAC distinct from eastern Mediterranean populations of this species. Intraspecific genetic diversity was evaluated at spatial and temporal scale for population samples recorded during the survey period, providing valuable information for individual resampling traceability and delineating management units. Temporal stability in genetic diversity and gene flow with adjacent areas were observed for dominant species within each NP in the 3‐year period studied. However, significant intraspecific differentiation was detected between populations identified in Atlantic and Mediterranean NPs. This study provides valuable reference genetic data for future monitoring and to identify distribution or research gaps for further studies towards the conservation of syngnathid populations in Spanish marine NPs, which serve as umbrella species for the preservation of vulnerable coastal ecosystems and habitats.