Endemic rodents of Hispaniola: biogeography and extinction timing during the Holocene

Hispaniola is the second-largest island in the West Indies bioregion and along with Cuba is considered the cradle of Greater Antillean rodent evolution and diversification. While the fossil record in Hispaniola includes ten extinct species of late Quaternary rodents, only a single species, the Hispaniola hutia (Plagiodontia aedium), is extant on the island. Changes in climate and anthropogenic effects have been suggested as drivers for these extinctions, but there are few radiometric dates associated with these fossils which limits our understanding of the timing of rodent extinctions on Hispaniola relative to shifts in Holocene climate and major events in human settlement and colonization. We report nine new AMS radiocarbon dates for six endemic rodents of Hispaniola that, when coupled with previously reported dates, provide last occurrence records for eight of the ten extinct rodent species there. Results show that Hispaniola rodent extinction occurred in a series of episodes, with more than half (63.6%) surviving into the late Holocene (4200 cal BP to present), postdating the initial arrival of Ceramic Age Indigenous groups, with extinction likely only after European colonization. This pattern in Hispaniola is consistent with what recent studies have found on the timing of extinction of other terrestrial vertebrates in the West Indies. Results from analysis of stable isotopes of fossil bone suggest that the extinction of endemic rodents from Hispaniola largely also postdate habitat changes following the onset of drier conditions in the late Holocene, suggesting that while climate may have shaped the geographic distribution of species, it probably played a minimal direct role in their extinctions on Hispaniola.