Unravelling the peculiarities of island life: vicariance, dispersal and the diversification of the extinct and extant giant Galápagos tortoises

Research reveals that the evolutionary history of Galápagos tortoises is shaped by both dispersal and vicariance, challenging traditional assumptions about island colonization. Only three of five extinct or nearly extinct species represent independent evolutionary units, with dispersal from South America initiating around 3.2 million years ago (Ma) following the emergence of San Cristobal and Española islands. Subsequent dispersal to younger islands began at approximately 1.74 Ma, accompanied by multiple colonizations within the archipelago. Vicariant events, driven by island formation, coalescence, and separation, contributed to lineage diversification on Pinzón and Floreana dating from 1.26 and 0.85 Ma, respectively. This study integrates DNA data from extinct and extant species with geological information and human activity records, providing a comprehensive model for reconstructing the history of endangered taxa despite extinctions and human-mediated dispersal events.

POULAKAKIS, N., RUSSELLO, M., GEIST, D., & CACCONE, A. (2011). Unravelling the peculiarities of island life: vicariance, dispersal and the diversification of the extinct and extant giant Galápagos tortoises. Molecular Ecology, 21(1), 160–173. Portico. https://doi.org/10.1111/j.1365-294x.2011.05370.x