Interesting, so did the wolves that we now see in the Americas coexist with the 'bone crushers', or was there an episode of rapid evolution at the end of the Pleistocene?. This same question applies to the bison that survived into historic times, they are rather different from the species that went extinct.
Also one of the articles mentioned that the 'bone crushers' didn't compete with the dire wolves. Anyone know why? The dire wolves were well represented at La Brea. Did the two species stake out different ranges?
Allan Shumaker
Dear Allan (and others),
I must admit that the article itself is somewhat confusing. I had to read it twice. So much for peer-reviewers. However, some sort of clarification can be found in the “conclusion”:
Compared with extant gray wolves and Pleistocene gray wolves from Rancho La Brea, the eastern- Beringian ecomorph was hypercarnivorous with a craniodental morphology more capable of capturing, dismembering, and consuming the bones of very large mega-herbivores, such as bison. When their prey disappeared, this wolf ecomorph did as well, resulting in a significant loss of phenotypic and genetic diversity within the species. Conceivably, the robust ecomorph also was present in western Beringia in the Late Pleistocene, but specimens were not available for this study. A plausible scenario for the presence of two distinct Pleistocene gray wolves in North America relies on an early arrival of the more gracile wolf from the Old World and migration to areas below the Wisconsin ice sheet. This gray wolf insinuated itself into a carnivore guild that already contained forms both larger (dire wolf) and smaller (coyote) than itself. The presence of these two relatively common species (especially the dire wolf) seems to have prevented gray wolves from reaching high densities until after the demise of the dire wolf, approximately 10 ka BP [12]. The appearance of a more robust form of the gray wolf in eastern Beringia in the Late Pleistocene might represent evolution in situ or a secondary invasion from the Old World. Its success was favored by the absence of dire wolves north of the ice sheet [12]. Otherwise, the eastern-Beringian gray wolf would probably not have evolved in the same direction as the dire wolf, acquiring a more robust skull and dentition, because that would have increased ecological overlap between the two species. Instead, the eastern- Beringian gray wolf was well positioned as the dominant large, pack-hunting canid within a predator guild that included large felids, ursids, and two smaller canids, the dhole and coyote [1].
Greater extinction vulnerability of relatively specialized forms has been shown for other Pleistocene carnivores [13]. Species that did not survive were usually the largest and most carnivorous within their family. Among the felids, the large lion and saber tooth disappeared, whereas the relatively eurytopic puma and bobcat (Lynx rufus) survived. Among the bears, the species with the greatest dental specialization for carnivory, the short-faced bear, vanished, but the more omnivorous and smaller black (Ursus americanus) and brown bears remain [13]. Similarly, the dire wolf was lost, whereas the smaller gray wolf and coyote survived. However, the gray wolf did not survive unscathed—we show that at least one ecologically distinct form was lost and replaced by a smaller and more generalized form. Past studies of Pleistocene survivors [14–16] also demonstrated a loss of genotypic diversity but did not explore changes in morphologic diversity. Thus, there may be other extinctions of unique Pleistocene ecomorphs yet to be discovered.
I hope this helps.
Jacques
