Complete mitogenomes of the endangered Galapagos fur seal (Arctocephalus galapagoensis): new insights on its evolutionary history

Of the two otariid species endemic to the Galapagos Islands, the Galapagos fur seal (GFS, Arctocephalus galapagoensis) remains the least studied due to its remote distribution restricted to the western islands of the archipelago, a region uniquely influenced by the cold, productive Equatorial Undercurrent (EUC). This study presents the first two complete GFS mitogenomes, assembled from scat samples collected at the Cabo Douglas rookery on Fernandina Island, to contribute to elucidating the evolutionary history of this endangered species. Time-calibrated phylogenies indicate most Arctocephalus species form a monophyletic group.​ These also show GFS as sister to South American and New Zealand fur seals, diverging 1.91–1.68 MYA (million years ago). This divergence coincides with the early Pleistocene cooling (Gelasian–Calabrian transition), when colder oceans favored otariid dispersal, thus suggesting the time of arrival of fur seals to the Galapagos Islands. The Galapagos region, maintained by the EUC, likely served as a climate refugium enabling fur seal persistence in tropical waters despite later interglacial warming. This study underscores the utility of non-invasive genetic sampling and highlights the role of the Galapagos marine ecosystem as a climate refugia for biodiversity in the face of oceanic warming.