Pleistocene bears in the Swabian Jura (Germany): Genetic replacement, ecological displacement, extinctions and survival

摘要

Palaeogenetic investigations in three geographically close caves (Hohle Fels, Geissenkloesterle, and Sir-genstein) in the Ach Valley near Blaubeuren (Swabian Jura) document the sudden replacement of Ursus spelaeus by Ursus ingressus around 28,000 14C BP. New radiocarbon dates suggest an earlier immigration of Ursus ingressus and at least a partial coexistence with Ursus spelaeus some 4500 years before the ultimate replacement. These two genetic types of cave bears used the same caves for hibernation and had the same herbivorous diet, as shown by the stable isotope results. In contrast, sympatric brown bears (Ursus arctos) exhibited a clearly different ecology, as shown by the carnivorous pattern of their isotopic signatures, and probably did not use the caves as dens before the Last Glacial Maximum (LGM). Once established, the younger cave bear (Ursus ingressus) remained the only cave bear for only another circa 2000 years after the last appearance of the classical cave bear (Ursus spelaeus) in the Ach Valley and elsewhere. The final appearance of cave bear (sensu lato) is now dated to 25,560 ± 130 BP, disproving a refuge area of this species in the Swabian Jura. After the extinction of cave bears (sensu lato), brown bears took over their cave dens and their nutritional niche as they shift to a diet dominated by plant food.