Molecular phylogenetics of circumglobal Euphausia species (Euphausiacea: Crustacea)

Abstract

The speciation history of members of the krill genus Euphausia with continuous circumglobal distributions was investigated by phylogenetic and molecular clock analyses of their mitochondrial DNA. Molecular clock estimates for divergence times of Antarctic and sub-Antarctic species of Euphausia of ~15 million years ago were fairly close to the time of formation of the Antarctic Convergence, consistent with their vicariant speciation. However, the confidence limits quantified for these time estimates were large at ~11 million and ~25 million years. A divergence time of between ~10 million years for Euphausia triacantha and Euphausia longirostris suggested that migration across oceanographic fronts like the Antarctic Convergence may also lead to speciation in krill. Genetic differentiation between Euphausia vallentini and Euphausia lucens was found to be relatively minor and occurred between 0.76 million and 1.65 million years ago. These species have overlapping ranges, suggesting that there is potential for sympatric genetic differentiation in krill.