Population structure, demographic history, and selective processes: contrasting evidences from mitochondrial and nuclear markers in the European spiny lobster Palinurus elephas (Fabricius, 1787).

The European spiny lobster Palinurus elephas (Fabricius, 1787) is an ecologically and economically important species inhabiting a wide geographic range that extends from the North-east Atlantic and Azores to the Eastern Mediterranean. We investigated the population structure and evolutionary history of this species by both mitochondrial and microsatellite markers. Ten population samples covering a large part of the species distribution range (three samples from the Atlantic Ocean and seven from the Mediterranean Sea) were analyzed for a portion of the mitochondrial control region and seven polymorphic microsatellite loci. Both markers rejected the hypothesis of panmixia identifying two differentiated gene pools. The control region clearly distinguished the Atlantic and Mediterranean populations in two genetically separated groups. Microsatellites, also revealed two groups roughly associated to the Atlantic-Mediterranean separation, however, the Azores sample did not conform to this geographic scheme. Discrepancy between mitochondrial and nuclear markers emerged also when reconstructing the history of the species. Neutrality tests of the mitochondrial sequences indicated a departure from mutation-drift equilibrium that, combined to the mismatch analysis, pointed toward a sudden population expansion in both Atlantic and Mediterranean gene pools. Unexpectedly, microsatellites did not identify any signal of population expansion neither in the Atlantic pool nor in the Mediterranean one.