Low level of genetic divergence between Harpagifer fish species (Perciformes: Notothenioidei) suggests a Quaternary colonization of Patagonia from the Antarctic Peninsula

Abstract

The evolution of the marine benthic fauna of Antarctica has been shaped by geological and climatic atmospheric factors such as the geographic isolation of the continent and the subsequent installation of the Antarctic Circumpolar Current (ACC). Despite this isolation process, strong biogeographic links still exist between marine fauna from the Antarctic Peninsula and southern South America. Recent studies in different taxa have shown, for example, that shallow benthic organisms with long larval stages maintained contact after the physical separation of the continents and divergence may be associated with the intensification of the ACC in the late Miocene-early Pliocene. In this context, here we performed phylogenetic reconstructions and estimated the level of molecular divergence between congeneric species of Harpagifer, a marine notothenioid from the Antarctic Peninsula (Harpagifer antarcticus) and Patagonia (H. bispinis) using the mitochondrial control region. Phylogenies were reconstructed using Maximum Parsimony and Bayesian Inference, while the divergence time of H. antarcticus and H. bispinis was estimated following a relaxed Bayesian approach and assuming a strict molecular clock hypothesis. According to our estimation, the divergence between H. bispinis and H. antarcticus is more recent than expected if it was associated with the intensification of the ACC during the mid to late Miocene. We propose that climatic and oceanographic changes during the coldest periods of the Quaternary (i. e., Great Patagonian Glaciation, 1-0.9 Ma) and the northward migration of the Antarctic Polar Front may have assisted the colonization of southern South America by Harpagifer, from the Antarctic Peninsula via the Scotia Arc Islands.