Limited interspecific gene flow in the evolutionary history of the icefish genus Chionodraco

Hybridization and introgression are recognized as mechanisms promoting genetic variability during evolutionary radiations. We examined the impact of introgression in the process of speciation, focusing on the Antarctic icefish genus Chionodraco. Our analyses confirmed that the three Chionodraco species (Chionodraco hamatus, Chionodraco myersi, and Chionodraco rastrospinosus) were genetically distinctive, despite signals of past interspecific gene flow between C. hamatus and C. myersi that likely occurred during interglacial periods. However, in this study, no recent hybrids were identified. The lack of contemporary hybridization may be due to life-history traits and the type of marker used in the analysis. Our study emphasizes the importance of genomic approaches to detect subtle patterns of past hybridization accurately and highlights the significance of historical climate events in the demographic and evolutionary history of Antarctic notothenioids. Polar regions, and especially the Antarctic Peninsula, are now experiencing the fastest climate changes due to global warming. Understanding the impact of past climate events is fundamental to trace current modifications in species' genetic variability and distributions and predict future evolutionary trajectories. This knowledge is also vital for conservation efforts, including the implementation of marine protected areas.