Phylogeny of the genus Merluccius based on mitochondrial and nuclear genes.

Genus Merluccius is considered one of the most important groups within the Teleostei, and comprises 12 extant species distributed along the coasts of America, Europe and Africa, being its fisheries very important in these continents. Despite their noticeable economical importance for humans, to date the phylogeny of hakes has not been clearly established. In this study we used mitochondrial sequences (the ribosomal genes 12S rDNA and 16S rDNA, the coding gene cytochrome b and the control region) and the nuclear 5S rDNA conserved region in order to determine the phylogenetic and biogeographical relationships within the genus Merluccius. This is the first time that all the species of this genus recognized by the FAO are included in a phylogeny. Maximum Parsimony, Maximum Likelihood and Bayesian analyses of the mitochondrial sequences suggest that the geographical origin of the genus was the North Atlantic Ocean, and indicate that two main clades, early separated in the evolution, exist within the genus: one American (7 species) and one Euro-African (5 species). Among the American species, M. bilinearis seems to be the most ancient one, and the rise of the Panama Isthmus could act as a physical barrier leading to further processes of speciation. Within the Euro-African clade, successive events of geographical differentiation could explain the observed pattern of species distribution. Therefore, we propose both vicariant speciation and geographical dispersion as main mechanisms to explain the evolutionary history of the genus Merluccius.