Antarctic krill (Euphausia superba) are a species of planktonic pelagic crustacean found in Southern Ocean waters surrounding Antarctica. They are very abundant. In a recent study by Deagle et al (2015, Molecular Ecology, https://onlinelibrary.wiley.com/doi/full/10.1111/mec.13370) the authors studied the population genetics pattern of the species analysing 5 samples as in the picture. In your opinion, it is more likely that: