Genome admixture among four hare species in Iberia: focus on the broom hare ( Lepus castroviejoi )

Pleistocene climatic fluctuations have often driven range shifts and hybridization among related species, leaving present-day genomic footprints. In the Iberian Peninsula, Lepus timidus , after its post-deglaciation retreat, has left extensive mitochondrial DNA traces in three other hare species, but the genomic correlates and underlying biogeographic scenarios are still incompletely understood. This study focuses on Lepus castroviejoi , endemic to the Cantabrian region, using its non-Iberian sister species, L. corsicanus , for comparison. By analyzing coalescent patterns from 10 genomes, we estimate that these species remained isolated since their divergence, around 50,000 years ago, consistent with their current allopatry. Further analyses with 25 additional genomes indicate that small fractions of the L. castroviejoi genome originate from L. granatensis , L. timidus , and L. europaeus (0.72%, 0.08%, and 0.04%, respectively). Introgression dating based on tract lengths suggests L. granatensis was already admixed with L. timidus when it hybridized with L. castroviejoi , which could explain the granatensis - timidus ancestry tract junctions detected in L. castroviejoi . Genomic segments with such junctions contain genes enriched for cell signaling and olfactory receptor activity, possibly facilitating genetic exchange. This research demonstrates how genomic ancestry inferences can reveal complex multiway admixture histories and illuminate past biogeographic events.