Hic sunt dracones: ancient DNA from the extinct palaeofauna of the tiny Mediterranean archipelago of Columbretes and its implications for human visitation

The Columbretes archipelago in the Mediterranean is an example of deep isolation and sporadic human interaction during the Holocene. We recovered ancient DNA from 2,600-year-old microfauna and historical museum specimens to investigate the island's extinct fauna. Despite challenging preservation conditions, we successfully recovered mitogenomes from historical Vipera latastei specimens, and partial mitogenomes from snake, skink, and lizard subfossils. Phylogenetic analyses confirm the extinct Columbretes snake as Vipera latastei, sharing a haplotype with the historical specimen and clustering with modern populations from northeastern Iberia, validating its provenance and suggesting a single mitochondrial lineage since isolation. The extinct skink, Chalcides bedriagai, also shows affinities with eastern Iberia. These results point to a vicariant origin for the herpetofauna, likely isolated on the island following sea level rise after the Last Glacial Maximum. Conversely, a 2,600-year-old mouse incisor yielded a Mus musculus mitogenome, indicating Iron Age human-mediated introduction. Additionally, genomic analysis of a 11th-century CE human burial revealed an individual with genetic affinities to the Central Mediterranean and Balkans, highlighting medieval maritime mobility. This study resolves the long-debated Columbretes snake identity, traces biogeographic origins and illustrates the interplay of natural isolation and anthropogenic influence on the island biodiversity.