Climate change has led to extensive restructuring of the world’s oceans. Marine organisms have responded to new conditions through various biological mechanisms, including genomic adaptations. The increasing availability of next-generation DNA sequencing methods for studying non-model species has recently made it possible to investigate the genomic changes underlying environmental adaptations. This study used double-digest restriction site-associated DNA (ddRAD) sequence data to investigate the genomic basis of ecotype formation among currently recognized species and subspecies of bottlenose dolphins (genus Tursiops) in the Southern Hemisphere.
Genomic divergence at the subspecies level has been confirmed between the coastal common bottlenose dolphin (T. truncatus truncatus) and the coastal Lahille’s bottlenose dolphin (T. t. gephyreus) in the southwestern Atlantic (SWAO). Similarly, divergence at the subspecies level is suspected between the coastal (eastern Australia) Indo-Pacific bottlenose dolphin (T. aduncus) and the proposed Burrunan bottlenose dolphin (T. australis) from southern Australia. Coastal bottlenose dolphins generally exhibited lower genomic diversity than offshore lineages, a pattern that was particularly evident in T. t. gephyreus, which showed exceptionally low diversity. Genomic regions associated with cardiovascular, musculoskeletal, and energy production systems appear to have undergone repeated adaptive evolution in nearshore lineages in the Southern Hemisphere. We hypothesize that comparable selective pressures in the nearshore environment have driven similar adaptive responses in each lineage, thereby supporting the parallel evolution of nearshore bottlenose dolphins. As climate change alters marine ecosystems worldwide, it is crucial to gain an understanding of the adaptability of local species and populations.
Our study provides insights into key adaptive pathways that may be important for the long-term survival of whales and other organisms in a changing marine environment.
Genomic Divergence and the Evolution of Ecotypes in Bottlenose Dolphins (Genus Tursiops)