Connectivity patterns and gene flow among Chelon ramada populations

Abstract

Catadromous species, such as the thinlip grey mullet Chelon ramada (Risso 1827), exhibit complex life history traits and migratory behaviours that have different repercussions at the population level and species genetic structure. To study the genetic variation and infer patterns of gene flow and population connectivity along species’ distribution across the Northeast Atlantic coast and the Mediterranean Sea, 457 individuals from sixteen locations were genotyped using eleven microsatellite markers. The existence of a metapopulation with high gene flow was supported by the absence of significant genetic differentiation among locations or geographic clustering of samples. The Portuguese populations are important for the maintenance of connectivity among populations of the Mediterranean and Northeast Atlantic regions, as evidenced by the high degree of gene flow observed between the Portuguese coast and all populations from these two regions.Our findings suggest that the thinlip grey mullet display a high dispersal capability, that combined with continuous habitat availability and large population numbers (low commercial exploitation in the Atlantic region), allow the maintenance of a unique genetic group.