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Genes, bones and behavior reveal phylogenetic relationships of dogs and their extinct relatives

Phylogeny of extant and extinct dogs (Caninae) based on molecular, morphological and behavioral characters. Zoologica Scripta

Dogs (subfamily Caninae) is one of the most charismatic groups of mammals and ecologically important predators and scavengers. They originated in the Oligocene, more than 30 million years ago in the North American continent. In the late Tertiary, two main groups of Caninae – fox-like Vulpini and dog-like Canini – spread across the Bering Strait to Eurasia and Africa, where they gave rise to many species, ranging from fennec fox to Arctic fox, from golden jackal to grey wolf. One group of Canini in the North America spread through the newly-formed Isthmus of Panama to the South America, giving rise a large group called Cerdocyonina, that includes distinctive species such as the bush dog, the maned wolf or the Falkland Islands wolf, extinct in the 19th century.

In spite of considerable attention being paid to wild relatives of “man’s best friends”, their phylogenetic relationships remain unclear. The main points of contention concern the relationship between recent and extinct species, phylogenetic placement of distinct species such as the gray fox (Urocyon cinereoargenteus), the bat-eared fox (Otocyon megalotis), or the raccoon dog (Nyctereutes procyonoides), and the phylogenetic placement of the so-called hypercarnivorous species. Most dogs are omnivores, but some species, such as the African wild dog (Lycaon pictus), have become top predators with a diet consisting of more than 75% meat. It is unclear whether these species are related.

A team of researchers from the Department of Zoology, Faculty of Science of the University of South Bohemia, led by Jan Zrzavý, reconstructed phylogenetic relationships of 80 species of extant and extinct dogs, based on a combination of genetic, morphological and behavioral characters. Phylogenetic analysis has shown that the fox-like Vulpini form a group of successively diverging lineages that includes foxes of the genus Vulpes as well as the bat-eared fox and the raccoon dog. The gray fox represents the oldest surviving lineages of dogs, related to extinct genus Metalopex, not to other foxes. The dog-like Canini includes, besides a well-defined South American Cerdocyonina and a group that includes wolves and jackals of the Old and New World, a couple of isolated lineages: the African wild dog and two species of small African jackals of the genus Lupulella, that are not immediately related to other jackals. Recent hypercarnivorous species are not closely related. Hypercarnivory evolved at least four times independently in the evolution of dogs.

A series of experimental analyses, based on “turning off” characters that do not fossilize well and that are associated with hypercarnivory revealed an important issue: Characters that fossilize well (e.g., teeth, parts of the skull, or long bones) are often indicative of ecological (dietary) adaptations and are less reliable for phylogenetic reconstruction. It is a paradoxical that the only characters that allow us to infer a comprehensive phylogeny of both extant and extinct species are likely those that tend to muddle true phylogenetic relationships. Phylogenetic trees based on these characters groups together species that are ecologically similar (e.g., hypercarnivorous species) but not actually related, as evident from the conflict with other morphological and molecular-based characters. Our current knowledge of phylogeny and evolution of dogs is to some extent affected by this issue. This issue is by no means trivial. Extinct North American dogs have recently become an important model group for studying general evolutionary topics such as adaptive radiation, evolution of body size, and evolution of ecological adaptations. A reliable phylogeny is crucial for investigation of these questions.

Zrzavý, J., Duda, P., Robovský, J., Okřinová, I., & Pavelková Řičánková, V. (2018). Phylogeny of the Caninae (Carnivora): Combining morphology, behaviour, genes and fossilsZoologica Scripta.

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