Biogeography, habitat transitions and hybridization in a radiation of South American silverside fishes revealed by mitochondrial and genomic RAD data

HUGHES, LILY C.; CARDOSO, YAMILA P.; SOMMER, JULIE A.; CIFUENTES, ROBERTO; CUELLO, MARIELA; SOMOZA, GUSTAVO M.; GONZÁLEZ-CASTRO, MARIANO; MALABARBA, LUIZ R.; CUSSAC, VICTOR; HABIT, EVELYN M.; BETANCUR-R., RICARDO; ORTÍ, GUILLERMO

MOLECULAR ECOLOGY

WILEY-BLACKWELL PUBLISHING, INC

Año: 2020

0962-1083

Rivers and lake systems in the southern cone of South America have been widely influenced by historical glaciations, carrying important implications for the evolution of aquatic organisms, including prompting transitions between marine and freshwa- ter habitats and by triggering hybridization among incipient species via waterway connectivity and stream capture events. Silverside fishes (Odontesthes) in the region comprise a radiation of 19 marine and freshwater species that have been hypoth- esized on the basis of morphological or mitochondrial DNA data to have either tran- sitioned repeatedly into continental waters from the sea or colonized marine habitats following freshwater diversification. New double digest restriction-site associated DNA data presented here provide a robust framework to investigate the biogeo- graphical history of and habitat transitions in Odontesthes. We show that Odontesthes silversides originally diversified in the Pacific but independently colonized the Atlantic three times, producing three independent marine-to-freshwater transitions. Our results also indicate recent introgression of marine mitochondrial haplotypes into two freshwater clades, with more recurring instances of hybridization among Atlantic- versus Pacific-slope species. In Pacific freshwater drainages, hybridization with a marine species appears to be geographically isolated and may be related to glaciation events. Substantial structural differences of estuarine gradients between these two geographical areas may have influenced the frequency, intensity and evo- lutionary effects of hybridization events.