Eastern North Atlantic Strandings Validate Genetic Patterns in Pygmy and Dwarf Sperm Whales (Kogiidae)

Pygmy (Kogia breviceps) and dwarf (Kogia sima) sperm whales are among the least studied cetaceans due to their elusive behavior and low detectability at sea. Molecular approaches are therefore essential to clarify their taxonomy, population structure, and conservation status. We present new mitochondrial DNA data from stranded K. breviceps and K. sima specimens collected across the eastern North Atlantic, a region previously not represented in genetic studies. We analyzed fragments of the mitochondrial cytochrome b gene and control region from 56 individuals and integrated these data with publicly available sequences to place regional diversity within a global phylogeographic framework. Population genetics, phylogenetics, and haplotype network analyses showed a weak or absent population structure in K. breviceps across its range, whereas K. sima was consistently separated into Atlantic–Mediterranean and Indo-Pacific lineages, characterized by high genetic divergence. Eastern North Atlantic samples clustered within the Atlantic lineage and showed moderate genetic diversity, with a few locality-specific haplotypes identified. Overall, our results expand the genetic baseline for Kogiidae species in the eastern North Atlantic and support previous evidence of cryptic diversity within K. sima. Despite observational limitations, the relatively high genetic diversity observed in the two species provides cautiously optimistic indications of population health in this elusive cetacean family.