| Sardinian Dwarf Mammoth Mammuthus lamarmorai, Sardinian Giant Otter Megalenhydris barbaricina, Deer, Sardinian Dhole Cynotherium sardous and Giant Pica.|
in Rozzi, Lomolino, van der Geer, Silvestro, ... et Chase, 2023.
Illustration by Peter Schouten
Islands have long been recognized as distinctive evolutionary arenas leading to morphologically divergent species, such as dwarfs and giants. We assessed how body size evolution in island mammals may have exacerbated their vulnerability, as well as how human arrival has contributed to their past and ongoing extinctions, by integrating data on 1231 extant and 350 extinct species from islands and paleo islands worldwide spanning the past 23 million years. We found that the likelihood of extinction and of endangerment are highest in the most extreme island dwarfs and giants. Extinction risk of insular mammals was compounded by the arrival of modern humans, which accelerated extinction rates more than 10-fold, resulting in an almost complete demise of these iconic marvels of island evolution.
|Illustration of Sardinian Dwarf Mammoth Mammuthus lamarmorai, Sardinian Giant Otter Megalenhydris barbaricina, Deer, Sardinian Dhole Cynotherium sardous and Giant Pica.|
Artwork: Peter Schouten
Roberto Rozzi, Mark V. Lomolino, Alexandra A. E. van der Geer, Daniele Silvestro, S. Kathleen Lyons, Pere Bover, Josep A. Alcover, Ana Benítez-López, Cheng-Hsiu Tsai, Masaki Fujita, Mugino O. Kubo, Janine Ochoa, Matthew E. Scarborough, Samuel T. Turvey, Alexander Zizka and Jonathan M. Chase. 2023. Dwarfism and Gigantism Drive Human-mediated Extinctions on Islands. Science. 379(6636); 1054-1059. DOI: 10.1126/science.add8606
Islands often contain distinctive ecological conditions that can lead to unusual evolutionary trajectories such as dwarf mammoths and giant rats. Rozzi et al. looked across extant and extinct species from islands to determine whether these evolutionary “oddities” were more threatened and found that both dwarf and giant species were more at risk for extinction. Further, the arrival of humans, both deep in the past and in the present, accelerated their extinction. Island conditions have thus both generated these unusual species and protected them, at least until humans acquired the ability to cross oceans. —SNV