Abstract
The diversity of fish in the Ross Sea is remarkably high for the Southern Ocean, and species’ life-history traits, including long lifespans and extended larval durations, should promote dispersal, supporting the assumption that their populations are largely well-connected and homogeneous. While economically and ecologically important, few studies have conducted detailed population-genomic analyses of regional fish taxa to test assumptions about connectivity. Here, we used a Genotyping-By-Sequencing (GBS) method to analyse 255 individuals from 18 populations of 5 fish species: Chionobathyscus dewitti, Macrourus whitsoni, Macrourus caml, Muraenolepis sp, and Antimora rostrata. Findings reveal a complex mosaic of population genetic structure within the Ross Sea region among the 5 species, with 3 species (Macrourus whitsoni, Muraenolepis sp, Antimora rostrata) showing panmixia or weak structure. In comparison, 2 species (Chionobathyscus dewitti and Macrourus caml) showed significant population genetic structure. The results of Tajima’s D and outlier analyses indicated complex demographic histories, including evidence of expansion and purifying selection. These results suggest that population structure in Antarctic fishes is shaped by species-specific responses to physical barriers associated with regional oceanography and bathymetry, as well as by evolutionary history. Our findings emphasize the potential for variation that exists in Antarctic population processes, even across similar taxa, with important management implications for fisheries in and around the world’s largest marine protected area.