Pleistocene wolf
During the Pleistocene, wolves were widely distributed across the Northern Hemisphere. Some Pleistocene wolves, such as Beringian wolves and those from Japan, exhibited large body size in comparison to modern gray wolf populations. Genetic analysis of the remains of Late Pleistocene wolves suggest that across their range populations of wolves maintained considerable gene flow between each other and thus there was limited genetic divergence between them. Modern wolves mostly draw their ancestry from some Siberian populations of Late Pleistocene gray wolves, which largely replaced other gray wolf populations after the Last Glacial Maximum.
Taxonomy
Pleistocene wolves represent a distinct ecomorph of Canis lupus. The ancient wolf specimens from Europe have been classified as Canis lupus spelaeus Goldfuß, 1823 – the cave wolf.Biogeography
The Late Pleistocene era was a time of glaciation, climate change, and the advance of humans into isolated areas. During the Late Pleistocene glaciation, a vast mammoth steppe stretched from Spain eastwards across Eurasia and over Beringia into Alaska and the Yukon. The close of this era was characterized by a series of severe and rapid climate oscillations with regional temperature changes of up to, which has been correlated with megafaunal extinctions. There is no evidence of megafaunal extinctions at the height of the Last Glacial Maximum, indicating that increasing cold and glaciation were not factors. Multiple events appear to have caused the rapid replacement of one species by another one within the same genus, or one population by another within the same species, across a broad area. As some species became extinct, so too did the predators that depended on them.Ecological factors including habitat type, climate, prey specialization, and predatory competition will greatly influence grey wolf genetic population structure and cranio-dental plasticity. Therefore, within the Pleistocene wolf population, the variations between local environments would have encouraged a range of wolf ecotypes that were genetically, morphologically, and ecologically distinct from one another. The origin of the modern grey wolf is nested in the biogeography of wolf populations that lived during the Late Pleistocene. The grey wolf is one of the few large carnivores to survive the Late Pleistocene megafaunal extinctions, but similar to many other megafaunal species it experienced a global population decline towards the end of this era, which was associated with extinctions of ecomorphs and phylogeographic shifts in populations.
Genetics
A haplotype is a group of genes in an organism that are inherited together from a single parent. A haplogroup is a group of similar haplotypes that share a common ancestor with a single-nucleotide polymorphism. Mitochondrial DNA passes along a maternal lineage that can date back thousands of years.In 2010, a study compared DNA sequences that were 230 base pairs in length from the mitochondrial control region of 24 ancient wolf specimens from western Europe dated between 44,000–1,200 YBP with those of modern grey wolves. Most of the sequences could be represented on a phylogenetic tree. However, the haplotypes of the Himalayan wolf and the Indian grey wolf could not because they were 8 mutations apart from the other wolves, indicating distinct lineages which had previously been found in other studies. The study found that there were 75 different grey wolf mDNA haplotypes that include 23 in Europe, 30 in Asia, 18 in North America, 3 in both Europe and Asia, and 1 in both Europe and North America. These haplotypes could be allocated into two haplogroups that were separated from each other by 5 mutations. Haplogroup 1 formed a monophyletic clade. All other haplotypes were basal in the tree, and these formed 2–3 smaller clades that were assigned to haplogroup 2 that was not monophyletic.
Haplogroups 1 and 2 could be found spread 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 a haplogroup 2 predominance in this region for over 40,000 years before and after the Last Glacial Maximum. A comparison of current and past frequencies indicated that in Europe haplogroup 2 became outnumbered by haplogroup 1 over the past several thousand years but in North America haplogroup 2 became extinct and was replaced by haplogroup 1 after the Last Glacial Maximum. Access into North America was available between 20,000–11,000 years ago after the Wisconsin glaciation had retreated but before the Bering land bridge became inundated by the sea. Therefore, haplogroup 1 was able to enter into North America during this period.
Stable isotope analysis conducted on the bone of a specimen allows researchers to form conclusions about the diet, and therefore the ecology, of extinct wolf populations. This analysis suggests that the Pleistocene wolves from haplogroup 2 found in Beringia and Belgium preyed mainly on Pleistocene megafauna, which became rare at the beginning of the Holocene 12,000 years ago. One study found the Beringian wolf to be basal to all other grey wolves except for the extant Indian grey wolf and the extant Himalayan wolf. The Pleistocene Eurasian wolves have been found to be morphologically and genetically comparable to the Pleistocene eastern-Beringian wolves, with some of the ancient European and Beringian wolves sharing a common haplotype, which makes ecological similarity likely. Two ancient wolves from Ukraine dated around 30,000 YBP and the 33,000 YBP "Altai dog" had the same sequence as six Beringian wolves, and another from the Czech Republic dated 44,000 YBP had the same sequence as two Beringian wolves.
It has been proposed that the Pleistocene wolves across northern Eurasia and northern North America represented a continuous and almost panmictic population that was genetically and probably also ecologically distinct from the wolves living in this area today. The specialized Pleistocene wolves did not contribute to the genetic diversity of modern wolves, and the modern wolf populations across the Holarctic are likely to be the descendants of wolves from populations that came from more southern refuges. Extant haplogroup 2 wolves can be found in Italy, the Balkans and the Carpathian Mountains but rare elsewhere in Europe. In Asia, only four haplotypes have been identified as belonging to this haplogroup, and two of them occur in the Middle East. Haplogroup 2 did not become extinct in Europe, and if before the Last Glacial Maximum haplogroup 2 was exclusively associated with the wolf ecomorph specialized in preying on megafauna, it would mean that in Europe it was capable of adapting to changing prey.
In 2013, a mitochondrial DNA sequencing of ancient wolf-like canids revealed another separate lineage of 3 haplotypes that was found in 3 Late Pleistocene specimens from Belgium; however, it has not been detected in extant wolves.
One of these was the "Goyet dog".File:Phylogenetic tree for wolves.jpg|thumb|mDNA phylogenetic tree for wolves. Clades are denoted I–XIX. Key regions/haplotypes are indicated and new haplotypes are displayed in bold. Late Pleistocene samples are represented by the numbers 1–10. Beringian wolf haplotype found in the modern clade XVI from China.
In 2016, a study was undertaken due to concerns that previous mDNA studies may have been conducted with insufficient genetic resolution or limited geographical coverage and had not included sufficient specimens from Russia, China, and the Middle East. The study compared a 582 base pair sequence of the mitochondrial control region which gave twice the phylogenetic resolution of the 2010 study. The study compared the sequences of both modern wolves and ancient wolf specimens, including specimens from the remote areas of North America, Russia and China. The study included the [|Taimyr wolves], the Goyet "dog", the Altai "dog", Beringian wolves, and other ancient specimens.
The study found 114 different wolf haplotypes among 314 sequences, with the new haplotypes being found in Siberia and China. The phylogenetic tree resolved into 19 clades that included both modern and ancient wolves, which showed that the most basal clades included the Indian grey wolf and the Himalayan wolf, with a subclade of wolves from China and Mongolia falling within the Himalayan wolf clade. The two most basal North American haplotypes included the Mexican wolf and the Vancouver Island wolf, however the Vancouver Island wolf showed the same haplotype as a dog which indicates admixture, with the dog lineage basal to all extant North American subspecies. In Europe, the two most genetically distinct haplotypes form the Iberian wolf and separately the Italian wolf that was positioned close to the ancient wolves. The Greenland wolves all belonged to one haplotype that had been previously found among North American wolves and which indicates their origin from North America. The Eastern wolf was confirmed as a coyote/wolf hybrid. Wolves found in the regions of the Chukotka Peninsula, the North Korean border, Amur Oblast and Khakassia showed the greatest genetic diversity and with close links to all other wolves found across the holarctic. One ancient haplotype that had been found in Alaska and Russia was shared with some modern wolves found in China and Mongolia.
The previous finding of two wolf haplogroups was not clearly delineated in this study but it agreed that the genetic diversity of past wolves has been lost at the beginning of the Holocene in Alaska, Siberia, and Europe with limited overlap with modern wolves. For the ancient wolves of North America, instead of an extinction/replacement model suggested by a previous study, this study found substantial evidence of a population bottleneck in North America in which the ancient wolf diversity was almost lost around the beginning of the Holocene. In Eurasia, the loss of ancient lineages could not be simply explained and appears to have been slow across time with the reasons unclear.
A 2022 study suggested that there was relatively little genetic difference between Pleistocene wolf populations even prior to the Last Glacial Maximum expansion of Siberian wolves replacing other wolf populations due to high connectivity across their range, and that a small amount of local pre-LGM European wolf ancestry persisted in modern European wolves.
Genetic studies of Pleistocene-aged wolves from Siberia indicates that they did not form a monophyletic group to exclusion of modern wolves, but instead represented various offshoots from the modern wolves.