Beringian wolf

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Beringian wolf
Temporal range:
YBP
)
Two models of Beringian wolves created by paleo-artists working at the Yukon Beringia Interpretive Centre
Two models of Beringian wolves created by paleo-artists working at the Yukon Beringia Interpretive Centre
Scientific classificationEdit this classification
Domain: Eukaryota
Kingdom: Animalia
Phylum: Chordata
Class: Mammalia
Order: Carnivora
Family: Canidae
Genus: Canis
Species:
C. lupus

Population: †Beringian wolf
Image of the Bering land bridge being inundated with rising sea level across time
Animated map showing Beringia sea levels measured in meters from 21,000 years ago to present. Beringia once spanned the Chukchi Sea and the Bering Sea, joining Eurasia to North America.

The Beringian wolf is an extinct

ecomorph of the gray wolf and has been comprehensively studied using a range of scientific techniques, yielding new information on their prey species and feeding behaviors. It has been determined that these wolves are morphologically distinct from modern North American wolves and genetically basal to most modern and extinct wolves. The Beringian wolf has not been assigned a subspecies classification and its relationship with the extinct European cave wolf
(Canis lupus spelaeus) is not clear.

The Beringian wolf was similar in size to the modern

Pleistocene megafauna
possible. The Beringian wolf preyed most often on horse and steppe bison, and also on caribou, mammoth, and woodland muskox.

At the close of the Ice Age, with the loss of cold and dry conditions and the extinction of much of its prey, the Beringian wolf became extinct. The extinction of its prey has been attributed to the impact of

climate change, competition with other species, including humans, or a combination of both factors. Local genetic populations were replaced by others from within the same species or of the same genus
. Of the North American wolves, only the ancestor of the modern North American gray wolf survived. The remains of ancient wolves with similar skulls and dentition have been found in western Beringia (northeastern Siberia). In 2016, a study showed that some of the wolves now living in remote corners of China and Mongolia share a common maternal ancestor with one 28,000-year-old eastern Beringian wolf specimen.

Taxonomy

From the 1930s representatives of the

gray wolf).[5]

Gray wolves were widely distributed across North American during both the Pleistocene and historic period.[6] In 2007 Jennifer Leonard undertook a study based on the genetic, morphology, and stable isotope analyses of seventy-four Beringian wolf specimens from Alaska and the Yukon that revealed the genetic relationships, prey species, and feeding behavior of prehistoric wolves, and supported the classification of this wolf as C. lupus.[7][8] The specimens were not assigned a subspecies classification by Leonard, who referred to these as "eastern Beringian wolves".[9] A subspecies was possibly not assigned because the relationship between the Beringian wolf and the extinct European cave wolf (C. l. spelaeus) is not clear. Beringia was once an area of land that spanned the Chukchi Sea and the Bering Sea, joining Eurasia to North America. Eastern Beringia included what is today Alaska and the Yukon.[10]

Lineage

Basal wolf

DNA sequences can be mapped to reveal a phylogenetic tree that represents evolutionary relationships, with each branch point representing the divergence of two lineages from a common ancestor. On this tree the term basal is used to describe a lineage that forms a branch diverging nearest to the common ancestor.[11] Wolf genetic sequencing has found the Beringian wolf to be basal to all other gray wolves except for the modern Indian gray wolf and Himalayan wolf.[8]

As of 2020, the oldest known intact wolf remains belongs to a mummified pup dated 56,000 YBP that was recovered from the permafrost along a small tributary of Last Chance Creek near Dawson City, Yukon, Canada. A DNA analysis showed that it belonged to the Beringian wolf clade, that the most recent common ancestor of this clade dates to 86,700–67,500 YBP, and that this clade was basal to all other wolves except for the Himalayan wolf.[12]

Different genetic types of gray wolf

Phylogenetic tree with timing in years for Canis lupus[a]
250,000
120,000
80,000
31,000

Late Pleistocene wolf†

Indian plains wolf

Himalayan wolf

A

DNA sequences of modern wolves with those from thirty-four specimens dated between 1856 and 1915. The historic population was found to possess twice the genetic diversity of modern wolves,[16][17] which suggests that the mDNA diversity of the wolves eradicated from the western US was more than twice that of the modern population.[17] A 2007 study compared mDNA sequences of modern wolves with those from Beringian wolves. The twenty Beringian wolves yielded sixteen haplotypes that could not be found in modern wolves, compared with seven haplotypes that were found in thirty-two modern Alaskan and Yukon wolves. This finding indicates that Beringian wolves were genetically distinct from modern wolves[16][18] and possessed greater genetic diversity, and that there once existed in North America a larger wolf population than today.[8] Modern Alaskan wolves have not descended from the Beringian wolves but from Eurasian wolves which migrated into North America during the Holocene.[6]

Phylogenetic tree for wolves

haplogroup 1 North American wolves

haplogroup 1 most Eurasian wolves

haplogroup 2 some Eurasian wolves (including the Italian wolf)

haplogroup 2 Beringian wolves†

Himalayan wolf and Indian gray wolf

Simplified mDNA phylogeny for modern wolves and extinct Beringian wolves[8][19]

A 2010 study compared mDNA sequences of modern wolves with those from 24 ancient wolf specimens from western Europe dated between 44,000 and 1,200

years before present (YBP). The study found that the sequences could be allocated into two haplogroups.[8][16] Haplogroups 1 and 2 could be found among wolves across Eurasia but only haplogroup 1 could be found in North America. The ancient wolf samples from western Europe differed from modern wolves by 1 to 10 mutations, and all belonged to haplogroup 2, indicating its predominance in this region for over 40,000 years, both before and after the Last Glacial Maximum. A comparison of current and past frequencies indicates that in Europe haplogroup 2 became outnumbered by haplogroup 1 over the past several thousand years, but in North America haplogroup 2 – including the Beringian wolf – became extinct and was replaced by haplogroup 1 after the Last Glacial Maximum.[19][20] However, a 2016 study did not support the existence of two wolf haplogroups.[21]

A scenario consistent with the phylogenetic, ice sheet size, and sea-level depth data is that during the Late Pleistocene the sea levels were at their lowest. A single wave of wolf colonization into North America commenced with the opening of the

Cordilleran Ice Sheet 23,000 YBP during the Late Glacial Maximum. As wolves had been in the fossil record of North America but the genetic ancestry of modern wolves could be traced back only 80,000 years,[22][23] the wolf haplotypes that were already in North America were replaced by these invaders, either through competitive displacement or through genetic admixture. The replacement in North America of a basal population of wolves by a more recent one is consistent with the findings of earlier studies.[8][23][19]

Artist's impression of the Beringian wolf

The Beringian wolves are morphologically and genetically comparable to Late Pleistocene European wolves.

Megafaunal wolf.[28]

It is possible that a

panmictic (random mating) wolf population, with gene flow spanning Eurasia and North America, existed until the closing of the ice sheets,[23][19][29] after which the southern wolves became isolated, and only the Beringian wolf existed north of the sheets. The land bridge became inundated by the sea 10,000 YBP, and the ice sheets receded 12,000–6,000 YBP.[23] The Beringian wolf became extinct, and the southern wolves expanded through the shrinking ice sheets to recolonize the northern part of North America.[23][29] All North American wolves are descended from those that were once isolated south of the ice sheets. However, much of their diversity was later lost during the twentieth century due to eradication.[23][17]

Description

Beringian wolf coming up to human waist height, about as long as a human is in height
Beringian wolf size compared to a human

Olsen described the short-faced wolf skulls as follows:

The proportions of the skulls of these wolves that vary do so in the rostral area. The area of the skull that is anterior to the infraorbital foramen is noticeably foreshortened and constricted laterally in several of the skulls...Dishing of the rostrum, when viewed laterally, is evident in all of the short-faced skulls identified as Canis lupus from the Fairbanks gold fields. The occipital and supraoccipital crests are noticeably diminished compared to those found in average specimens of C. lupus. The occipital overhang of these crests, a wolf characteristic, is about equal in both groups of C. lupus...Examination of a large series of recent wolf skulls from the Alaskan area did not produce individuals with the same variations as those from the Fairbanks gold fields.[5]

The Beringian wolf was similar in size to the modern

hamstring muscles – indicating that they had comparatively more powerful leg muscles for a fast take-off before a chase.[32] The Beringian wolf was more robust, and possessed stronger jaws and teeth, than either Rancho La Brea or modern wolves.[8][16]

During the Late Pleistocene, the more southerly occurring dire wolf (Aenocyon dirus) had the same shape and proportions as the Yukon wolf,[33][34] but the dire wolf subspecies A. dirus guildayi is estimated to have weighed on average 60 kg (130 lb), and the subspecies A. dirus dirus on average 68 kg (150 lb), with some specimens being larger.[35] The dire wolf was heavier than the Beringian wolf and possessed a more robust skull and dentition.[8]

Adaptation

ecotypes that were genetically, morphologically, and ecologically distinct from each another.[37] The term ecomorph is used to describes a recognizable association of the morphology of an organism or a species with their use of the environment.[39] The Beringian wolf ecomorph shows evolutionary craniodental plasticity not seen in past nor present North American gray wolves,[8] and was well-adapted to the megafauna-rich environment of the Late Pleistocene.[8][9]

Paleoecology

Map showing higher rainfall across southern coastal Beringia than in the north
Beringia precipitation 22,000 years ago

The

Pleistocene megafauna, near the end of the last glaciation.[43]

During the Ice Age a vast, cold and dry mammoth steppe stretched from the Arctic islands southwards to China, and from Spain eastwards across Eurasia and over the Bering land bridge into Alaska and the Yukon, where it was blocked by the Wisconsin glaciation. The land bridge existed because sea levels were lower due to more of the planet's water being locked up in glaciers compared with today. Therefore, the flora and fauna of Beringia were more related to those of Eurasia rather than to those of North America.[44][45] In eastern Beringia from 35,000 YBP the northern Arctic areas experienced temperatures 1.5 °C (2.7 °F) warmer than today, but the southern sub-Arctic regions were 2 °C (3.5 °F) cooler. In 22,000 YBP, during the Last Glacial Maximum, the average summer temperature was 3–5 °C (5.4–9 °F) cooler than today, with variations of 2.9 °C (5.2 °F) cooler on the Seward Peninsula to 7.5 °C (13.5 °F) cooler in the Yukon.[46]

Beringia received more moisture and intermittent maritime cloud cover from the north Pacific Ocean than the rest of the Mammoth steppe, including the dry environments on either side of it. Moisture occurred along a north–south gradient with the south receiving the most cloud cover and moisture due to the airflow from the North Pacific.

woodland muskox (Symbos cavifrons) consumed tundra plants, including lichen, fungi, and mosses.[10]

Prey

Bison surrounded by a gray wolf pack. Beringian wolves preyed most often on steppe bison and horse.

Isotope analysis can be used to allow researchers to make inferences about the diet of the species being studied. Two isotope analyses of bone collagen extracted from the remains of Late Pleistocene wolves found in Beringia and Belgium indicate that wolves from both areas preyed mainly on Pleistocene megafauna,[8][19][51] which became rare at the beginning of the Holocene 12,000 years ago.[19][52] The Beringian wolf preyed most often on horse and steppe bison.[8][18] In the period leading up to the Last Glacial Maximum (50,000 YBP–23,000 YBP), they also ate woodland muskox, and after this time they also ate mammoth. The analysis supports the conclusion that these wolves were capable of killing and dismembering large prey.[8]

In another stable isotope analysis, half of the Beringian wolves were found to be musk ox and caribou specialists, and the other half were either horse and bison specialists or generalists. Two wolves from the full-glacial period (23,000–18,000 YBP) were found to be mammoth specialists, but it is not clear if this was due to scavenging or predation. The analysis of other carnivore fossils from the Fairbanks region of Alaska found that mammoth was rare in the diets of the other Beringian carnivores.[10]

A stable isotope analysis of a mummified Beringian wolf pup dated 56,000 YBP that was recovered near the Klondike river revealed that most of its diet - and therefore its mother's diet - was based on aquatic rather than animal resources. The aquatic resources was proposed to be salmon.[12]

Dentition

A 2007 study of

hypercarnivorous lifestyle.[8][16]

An accepted sign of domestication is the presence of tooth crowding, in which the orientation and alignment of the teeth are described as touching, overlapping or being rotated. However, a 2017 study found that 18% of Beringian wolf specimens exhibit tooth crowding compared with 9% for modern wolves and 5% for domestic dogs. These specimens predate the arrival of humans and therefore there is no possibility of cross-breeding with dogs. The study indicates that tooth crowding can be a natural occurrence in some wolf ecomorphs and cannot be used to differentiate ancient wolves from early dogs.[54]

Diagram of a wolf skull with key features labelled
North American gray wolves compared by mean mandible tooth measurements (millimeters)[8]
Tooth variable modern North America Rancho La Brea Eastern Beringia
premolar row length 63.4 63.6 69.3
palate width 64.9 67.6 76.6
P4 length 25.1 26.3 26.7
P4 width 10.1 10.6 11.4
M1 length 16.4 16.5 16.6
M2 length 8.7 8.9 9.2
m1 length 28.2 28.9 29.6
m1
trigonid
length 		19.6 21.9 20.9
m1 width 10.7 11.3 11.1

Tooth breakage

Dentition of an Ice Age wolf showing functions of the teeth

Tooth breakage is related to a carnivore's behavior.

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 the incisors and then cracked with the carnassials and molars.[8] The risk of tooth fracture is also higher when taking and consuming large prey.[57][58]

Competitors

In addition to the Beringian wolf, other Beringian carnivores included the

scimitar-toothed cat (Homotherium serum), giant short-faced bear (Arctodus simus), and the omnivorous brown bear (Ursus arctos).[10] Beringian wolves would have faced competition for the carcasses of large herbivores from the formidable giant short-faced bear, a scavenger.[59] Additionally, humans had reached the Bluefish Caves in the Yukon Territory by 24,000 YBP, with cutmarks being found there on specimens of Yukon horse, steppe bison, caribou (Rangifer tarandus), wapiti (Cervus canadensis), and Dall sheep (Ovis dalli).[60]

A 1993 study proposed that the higher frequency of tooth breakage among Pleistocene carnivores compared with living carnivores was not the result of hunting larger game, something that might be assumed from the larger size of the former. When there is low prey availability, the competition between carnivores increases, causing them to eat faster and consume more bone, leading to tooth breakage.[55][61][62] Compared to modern wolves, the high frequency of tooth fracture in Beringian wolves indicates higher carcass consumption due to higher carnivore density and increased competition.[8] This proposal was challenged in 2019, when a survey of modern wolf behavior over the past 30 years showed that when there was less prey available, the rates of tooth fracture more than doubled. This suggests that large Pleistocene carnivores experienced more periods of limited food availability when compared with their modern counterparts.[63]

Range

Path of Beringian wolves from Alaska to the Natural Trap Cave, Wyoming (denoted with a black dot). Dog icons represent sites where Beringian wolves have previously been found, and paw prints represent the proposed path through the ice sheets.[9]

The remains of Beringian wolves have been found in Alaska and as far eastward as the Yukon in Canada.[9] Specimens that have been identified by their skull morphology[9] and limb morphology[64] to be Beringian wolves have been found in the Natural Trap Cave at the base of the Bighorn Mountains in Wyoming, United States. These were radiocarbon dated to between 25,800 and 14,300 YBP, and this location is directly south of what would at that time have been the division between the Laurentide Ice Sheet and the Cordilleran Ice Sheet. This suggests that a temporary channel existed between the glaciers from 25,800 YBP[9] until the advance of the ice sheets 16,000–13,000 YBP.[9][65] The migration of the Beringian wolf southwards is assumed to have been the result of pursuing prey species, as this cave also contained specimens of steppe bison that had migrated from Beringia and would have been prey for wolves,[9][66] and musk ox that is known to be an important prey species of the Beringian wolf.[9][10] Dire wolves were absent north of 42°N latitude in the Late Pleistocene; therefore, this region would have been available for Beringian wolves to expand southwards. There is no evidence of expansion beyond this region.[9]

Extinction

Ubsunur Hollow Biosphere Reserve
on the border between Russia and Mongolia, is one of the last remnants of the mammoth steppe.

Extinction is the result of the elimination of the geographic range of a species with a reduction of its population size down to zero. The factors that affect biogeographic range and population size include competition, predator-prey interactions, variables of the physical environment, and chance events.[67]

Phenotype is extinct

A

climate change, competition with other species, including humans, or a combination of both factors.[58][73] For those mammals with modern representatives, ancient DNA and radiocarbon data indicate that the local genetic populations were replaced by others from within the same species or by others of the same genus.[74]

Phylogenetic tree based on the mDNA of wolves. The modern wolf clade XVI from China/Mongolia shares a haplotype with a Beringian wolf (Alaska 28,000 YBP).

Postglacial environmental change throughout eastern Beringia brought about wholesale changes in vegetation, the regional extinction of much of the megafauna, and the entrance of

Homo sapiens.[46] The large Late Pleistocene carnivores that were more carnivorous than their competitors faced greater vulnerability to extinction. The Beringian cave lion, saber-toothed cat, and short-faced bear went extinct at the same time as their large megafaunal prey. The omnivorous coyote, American black bear, brown bear, puma and bobcat survived. Both the Beringian wolf and the dire wolf went extinct in North America, leaving only the less carnivorous and more gracile form of the wolf to thrive.[8] One extinction theory holds that the Beringian wolf was outcompeted and replaced by the ancestor of the modern gray wolf.[9]

The radiocarbon dating of the skeletal remains from 56 Beringian wolves showed a continuous population from over 50,800 YBP[21] until 12,500 YBP, followed by one wolf dated at 7,600 YBP. This indicates that their population was in decline after 12,500 YBP,[8] although megafaunal prey was still available in this region until 10,500 YBP.[75] The timing of this latter specimen is supported by the recovery of mammoth and horse DNA from sediments dated 10,500 YBP–7,600 YBP from the interior of Alaska,[75] and steppe bison dated 5,400 YBP from the Yukon.[76] The timing for the extinction of horses in North America and the minimum population size for North American bison coincide with the extinction of an entire wolf haplogroup in North America, indicating that the disappearance of their prey caused the extinction of this wolf ecomorph.[16][18] This resulted in a significant loss of phenotypic and genetic diversity within the species.[8]

Haplotype is not extinct

There are parts of Central Eurasia where the environment is considered to be stable over the past 40,000 years.

Urals 18,000 YBP) was shared by modern wolves found living in Mongolia and China (indicating a common maternal ancestor). The study found that the genetic diversity of past wolves was lost at the beginning of the Holocene in Alaska, Siberia, and Europe, and that there is limited overlap with modern wolves. The study did not support two wolf haplogroups that had been proposed by earlier studies. For the ancient wolves of North America, instead of an extinction/replacement model indicated by other studies, this study found substantial evidence of a population bottleneck (reduction) in which the ancient wolf diversity was almost lost at the beginning of the Holocene. In Eurasia, the loss of many ancient lineages cannot be simply explained and appears to have been slow across time with reasons unclear.[21]

Descendants

In 2021, an mDNA analysis of modern and extinct North American wolf-like canines indicates that the Beringian wolf was the ancestor of the southern wolf clade, which includes the Mexican wolf and the extinct Great Plains wolf. The Mexican wolf is the most ancestral of the gray wolves that live in North America today. The modern coyote appeared around 10,000 years ago. The most genetically basal coyote mDNA clade pre-dates the Late Glacial Maximum and is a haplotype that can only be found in the Eastern wolf. This implies that the large, wolf-like Pleistocene coyote was the ancestor of the Eastern wolf. Further, another ancient haplotype detected in the Eastern wolf can be found only in the Mexican wolf. The study proposes that Pleistocene coyote and Beringian wolf admixture led to the Eastern wolf long before the arrival of the modern coyote and the modern wolf.[78]

Notes

  1. ^ For a full set of supporting references refer to the note (a) in the phylotree at Evolution of the wolf#Wolf-like canids

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External links
Retrieved from "https://en.wikipedia.org/w/index.php?title=Beringian_wolf&oldid=1221936915"