DNA barcoding reveals deep divergent molecular units in Pomatomus saltatrix (Perciformes: Pomatomidae): implications for management and global conservation

Abstract

Pomatomus saltatrix is a high-value marine pelagic coastal fish, that is fished throughout subtropical and temperate coastal waters around the world. Despite its large economic potential, there are no global data on its genetic diversity, which could compromise the conservation of the species. The aim of this study was to analyse the genetic-evolutionary structuring of the species, with the intention of evaluating different genetic P. saltatrix stocks that may indicate potential species. Based on 157 Cytochrome C Oxidase Subunit 1 sequences, the molecular delimitation analyses of species (distance and coalescence methods), as well as the haplotype network, found profound geographic structuring related to five distinct units with high and significant FST pairwise values. The divergence of these molecular units is mostly related to the Pleistocene glacial and interglacial cycles of climatic oscillations. It is hypothesized that one ancestral lineage, adapted to cold water environments, diversified into two lineages, with one more adapted to warmer environments. The high values of global genetic diversity (π = 0.016; h = 0.96) may be related to the existing profound genetic differentiation. Due to the presence of five Molecular Operational Taxonomic Units (MOTUs) within the species it is necessary to employ different regional management strategies. Traits of low haplotype richness and shallow population contraction were identified in the MOTUs V (Venezuela and Brazil) and III (Turkey and Australia), respectively, representing conservation priorities. Other molecular markers, as well as morphological data, should be explored with the aim of defining the taxonomic status of P. saltatrix stocks.