Testing species boundaries between Atlantic and Pacific lineages of the Patagonian rockfish Sebastes oculatus (Teleostei: Scorpaenidae) through mitocondrial DNA sequences

Genetic differentiation and species boundaries between Atlantic and Pacific lineages of the Patagonian rockfish Sebastes oculatus was investigated using mtDNA D-loop partial sequences (541 bp). Sequences were obtained for 47 individuals from seven locations off the Pacific and Atlantic coasts of South America (S. oculatus) and one off the coast of South Africa (S. capensis), and for two specimens of Helicolenus lengerichi (outgroup). These data were then combined with sequences from GenBank corresponding to 21 Sebastes species. Maximum likelihood and Bayesian phylogenetic approaches showed topological distinctiveness between South American and South African Sebastes populations, supporting the existence of two phylogenetic species: S. oculatus and S. capensis. However, Atlantic and Pacific populations of S. oculatus, did not form reciprocal monophyletic assemblages. Application of the Wiens & Penkrot’s protocol to test species boundaries within this species did not support the existence of two different phylogenetic taxa. Gene flow between Atlantic and Pacific populations of S. oculatus could be explained by extensive larval dispersal, favored by both the Humboldt current and the West Wind Drift current along the South American coast.