Dokdo sea lionZalophus japonicusgenome reveals its evolutionary trajectory before extinction

Abstract

AbstractBackgroundThe Dokdo sea lion (Zalophus japonicus), commonly referred to as Gangchi in Korea and known as the Japanese sea lion, was endemic to the Northwest Pacific coast before becoming extinct in the 1950s. Little is known about its origins, speciation compared to otherOtariidaespecies or how the rapid decline affected the species’ genetic diversity.ResultsTo raise the Dokdo sea lion from this relative obscurity, we sequenced DNA from 16Z. japonicus’ bone fragments, obtained from Dokdo and Ulleungdo islands in Korea. Our analysis establishesZ. japonicusas the earliest diverged species within its genus, significantly redefining its evolutionary relationship with the California (Z. californianus) and Galapagos (Z. wollebaeki) sea lions. This genome-scale analysis clarifies the phylogeny ofZ. japonicus, shedding light on its speciation and the evolutionary pathways that shaped its genetic diversity before its extinction. In addition, we discovered, population decline of theZ. japonicusstarted already 1,000 years ago, however,Z. japonicusgenome maintained a relatively high heterozygosity despite, nearing extinction.ConclusionsOur genome-scale analysis eliminated ambiguity inZ. japonicusphylogeny, and shed light on the evolutionary pathways underlying its speciation. This study highlights the importance of the genome-scale analysis for extinct species to understand their complex evolutionary histories and conservation status.