Beringian wolf

Shrinking of the Bering land bridge

The Beringian wolf was a hypercarnivorous ecomorph of gray wolf which inhabited eastern Beringia (modern day Alaska) during the Late Pleistocene. It was similar in size to other Pleistocene gray wolves and modern Alaskan wolves, but had a shorter, broader palate, with large carnassials relative to its overall skull size. This adaptation allowed it to predate and scavenge on Pleistocene megafauna.[1]

Lineage

A study on the skeletal material from 56 wolves based on uncalibrated radio carbon dating showed a continuous population from 45,500 years BP to 12,500 years BP, and one single wolf dated at 7,600 BP. This indicates that their population was in decline after 12,500 BP,[1] although megafauna was still available in this region until 10,500 BP.[2]:22352 The latter specimen is supported by the discovery of a remaining pocket of residual megafauna that still inhabited interior Alaska around that time.[2]:22353

None of the 16 mtDNA haplotypes recovered from a sample of 20 Pleistocene eastern-Beringian wolves was shared with any modern gray wolf, but similar haplotypes were found in Late Pleistocene Eurasian gray wolves. Six eastern-Beringian wolves had the same sequence found in two wolves from Ukraine dated 30,000 years BP and 28,000 years BP, and from Altai dated 33,000 years BP. Two eastern-Beringian wolves matched another haplotype with a wolf from the Czech Republic dated at 44,000 years BP. Its phylogeny indicates that, aside from the modern Canis lupus pallipes, the Beringian wolf's unique haplotypes are basal to other gray wolves. Its genetic diversity was higher than that of its modern counterparts, implying that the wolf population of the Late Pleistocene was larger than present. Modern North American wolves are not their descendents, and this supports the existence of a separate origin for ancient and extant North American wolves.[1]

A more detailed analysis of the genetic material from three specimens were dated at 28,000 years BP, 21,000 years BP, and 20,800 years BP respectively (with the samples deposited in GenBank with accession numbers KF661088, KF661089 and KF661090) and classified as Canis lupus.[3]

Morphology

Beringian wolves were similar in physical size to Pleistocene wolves found in Rancho La Brea (California) and modern Alaskan wolves, but with stronger jaws and teeth. Beringian wolves tended to have short, broad palates with large carnassials relative to their overall skull size. Together, these features suggest a gray wolf adapted for producing relatively large bite forces. The short, broad rostrum increased the mechanical advantage of a bite made with the canine teeth and strengthened the skull against torsional stresses caused by struggling prey. Relatively deep jaws are characteristic of habitual bone crackers, such as spotted hyenas, as well as canids that take prey as large as or larger than themselves. Overall these features indicate that eastern-Beringian wolves were more specialized than modern gray wolves in killing and consuming relatively large prey and/ scavenging.[1][4]

In comparison to other gray wolf populations, Beringian wolf samples include many more individuals with moderately to heavily worn teeth. In addition, eastern-Beringian wolves exhibit heavier wear and significantly greater numbers of broken teeth. Overall fracture frequencies ranged from a low of 2% in Canis lupus irremotus (Canada, Idaho) to a high of 11% in the eastern-Beringian wolves. The distribution of fractures across the tooth row differs as well, with eastern-Beringian wolves having much higher fracture frequencies of incisors, carnassials, and molars. A similar pattern was observed in spotted hyenas, suggesting that increased incisor and carnassial fracture reflects habitual bone consumption, because bones are gnawed with incisors and subsequently cracked with the cheek teeth.[1]

Ecology

Habitat

Conceivably, the robust ecomorph also was present in western Beringia (Russia) in the Late Pleistocene,[5] 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 established 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 10,000 years BP. 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.[1]

Diet

Isotopic bone collagen analysis of the specimens indicated that they ate horse, bison, woodland muskox and mammoth i.e. Pleistocene megafauna. This supports the conclusion that they were capable of killing and dismembering large prey.[1]

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.[1]

A more in-depth analysis based on fossil findings in the Fairbanks region of Alaska found that mammoth was rare in the diets of Beringian carnivores – the short-faced bears, lions, Beringian wolves, and the omnivorous brown bear. Half of the wolf specimens were found to be muskox and caribou specialists, and the other half were horse and bison specialists or generalists. Two full-glacial (23,000–18,000 years BP) wolves were found to be mammoth specialists but we cannot tell if this was due to scavenging or predation. The only survivor of this guild was the brown bear, an omnivore.[6]

Competitors

The eastern-Beringian 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. One study[7] found that the coyote of 10,000 years ago was more canivorous, much larger, and with skulls and jaws significantly thicker and deeper than those of recent populations.[8]

See also

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 1.5 1.6 1.7 Leonard, J. A.; Vilà, C; Fox-Dobbs, K; Koch, P. L.; Wayne, R. K.; Van Valkenburgh, B (2007). "Megafaunal extinctions and the disappearance of a specialized wolf ecomorph". Current Biology 17 (13): 1146–50. doi:10.1016/j.cub.2007.05.072. PMID 17583509.
  2. ↑ 2.0 2.1 Haile, J.; Froese, D. G.; MacPhee, R. D. E.; Roberts, R. G.; Arnold, L. J.; Reyes, A. V.; Rasmussen, M.; Nielsen, R.; Brook, B. W.; Robinson, S.; Demuro, M.; Gilbert, M. T. P.; Munch, K.; Austin, J. J.; Cooper, A.; Barnes, I.; Moller, P.; Willerslev, E. (2009). "Ancient DNA reveals late survival of mammoth and horse in interior Alaska". Proceedings of the National Academy of Sciences 106 (52): 22352. Bibcode:2009PNAS..10622352H. doi:10.1073/pnas.0912510106.
  3. ↑ Thalmann, O.; Shapiro, B.; Cui, P.; Schuenemann, V. J.; Sawyer, S. K.; Greenfield, D. L.; Germonpré, M. B.; Sablin, M. V.; López-Giráldez, F.; Domingo-Roura, X.; Napierala, H.; Uerpmann, H-P.; Loponte, D. M.; Acosta, A. A.; Giemsch, L.; Schmitz, R. W.; Worthington, B.; Buikstra, J. E.; Druzhkova, A.; Graphodatsky, A. S.; Ovodov, N. D.; Wahlberg, N.; Freedman, A. H.; Schweizer, R. M.; Koepfli, K.-.P.; Leonard, J. A.; Meyer, M.; Krause, J.; Pääbo, S.; Green, R. E.; Wayne, R. K. (2013). "Complete Mitochondrial Genomes of Ancient Canids Suggest a European Origin of Domestic Dogs". Science 342 (6160): 871–74. doi:10.1126/science.1243650.
  4. ↑ Rozell, Ned (October 3, 2012). "Mystery wolf didn't survive in Alaska". Geophysical Institute, University of Alaska – Fairbanks. Retrieved February 19, 2015.
  5. ↑ Baryshnikov, Gennady F.; Mol, Dick; Tikhonov, Alexei N (2009). "Finding of the Late Pleistocene carnivores in Taimyr Peninsula (Russia, Siberia) with paleoecological context". Russian Journal of Theriology (Russian Journal of Theriology) 8 (2): 107–113. Retrieved December 23, 2014.
  6. ↑ Fox-Dobbs, K.; Leonard, J. A.; Koch, P. L. (2008). "Pleistocene megafauna from eastern Beringia: Paleoecological and paleoenvironmental interpretations of stable carbon and nitrogen isotope and radiocarbon records". Palaeogeography, Palaeoclimatology, Palaeoecology 261: 30. doi:10.1016/j.palaeo.2007.12.011.
  7. ↑ Meachen, J. A.; Samuels, J. X. (2012). "Evolution in coyotes (Canis latrans) in response to the megafaunal extinctions". Proceedings of the National Academy of Sciences 109 (11): 4191. doi:10.1073/pnas.1113788109. PMID 22371581.
  8. ↑ "Coyotes "Shrank," Wolves Did Not, After Last Ice Age and Megafaunal Extinctions". National Science Foundation. February 27, 2012. Retrieved December 20, 2014.