Modern Canids Research Articles

Natural and human-driven selection of a single non-coding body size variant in ancient and modern canids

Domestic dogs (Canis lupus familiaris) are the most variable-sized mammalian species on Earth, displaying a 40-fold size difference between breeds.1 Although dogs of variable size are found in the archeological record,2-4 the most dramatic shifts in body size are the result of selection over the last two centuries, as dog breeders selected and propagated phenotypic extremes within closed breeding populations.5 Analyses of over 200 domestic breeds have identified approximately 20 body size genes regulating insulin processing, fatty acid metabolism, TGFβ signaling, and skeletal formation.6-10 Of these, insulin-like growth factor 1 (IGF1) predominates, controlling approximately 15% of body size variation between breeds.8 The identification of a functional mutation associated with IGF1 has thus far proven elusive.6,10,11 Here, to identify and elucidate the role of an ancestral IGF1 allele in the propagation of modern canids, we analyzed 1,431 genome sequences from 13 species, including both ancient and modern canids, thus allowing us to define the evolutionary history of both ancestral and derived alleles at this locus. We identified a single variant in an antisense long non-coding RNA (IGF1-AS) that interacts with the IGF1 gene, creating a duplex. While the derived mutation predominates in both modern gray wolves and large domestic breeds, the ancestral allele, which predisposes to small size, was common in small-sized breeds and smaller wild canids. Our analyses demonstrate that this major regulator of canid body size nearly vanished in Pleistocene wolves, before its recent resurgence resulting from human-imposed selection for small-sized breed dogs.

The nature of coxofemoral joint pathology across family Canidae.

We evaluated coxofemoral joints from museum specimens of: Vulpes lagopus; Vulpes vulpes; Vulpes velox; Nyctereutes procyonoides; Urocyon cinereoargenteus; Aenocyon [Canis] dirus; Canis latrans; Canis lupus lupus; Canis lupus familiaris; C. l. familiaris × latrans; and Canis dingo. Acetabular components included: fossa; articular surface; medial and lateral articular margins; and periarticular surfaces. Acetabular components variably revealed: osteophyte-like features; varying appearance of articular margin rims (especially contour changes); rough bone surfaces (especially fossa and articular surface); and surface wear. Proximal femoral components included: articular surface; articular margin; periarticular surfaces; and joint capsule attachment. Femoral components variably revealed: rough bone surface; bone loss; articular margin osteophyte-like features; caudal post-developmental mineralized prominence; and enthesophytes along the joint capsule attachment. Non-metric multidimensional scaling was used to analyze right-left asymmetric relationships between observed traits, across taxa. Significantly different acetabular trait asymmetry involved only C. latrans-C. l. familiaris; V. vulpes-N. procyonoides, and U. cinereoargenteus-N. procyonoides. There were no significant lateralized differences in proximal femoral traits involving modern canids, ancient and modern C. l. familiaris, or modern vulpines. Thus, the observations were strongly bilateral. We hypothesized high similarity of traits across taxa. The data confirm the hypothesis and strongly suggest broad and deep morphological and mechanistic conservation that almost certainly pre-existed (at least) all modern canids. Further zoological studies are needed to evaluate phylogenic implications in greater detail.

Dog10K: an international sequencing effort to advance studies of canine domestication, phenotypes and health.

ABSTRACTDogs are the most phenotypically diverse mammalian species, and they possess more known heritable disorders than any other non-human mammal. Efforts to catalog and characterize genetic variation across well-chosen populations of canines are necessary to advance our understanding of their evolutionary history and genetic architecture. To date, no organized effort has been undertaken to sequence the world's canid populations. The Dog10K Consortium (http://www.dog10kgenomes.org) is an international collaboration of researchers from across the globe who will generate 20× whole genomes from 10 000 canids in 5 years. This effort will capture the genetic diversity that underlies the phenotypic and geographical variability of modern canids worldwide. Breeds, village dogs, niche populations and extended pedigrees are currently being sequenced, and de novo assemblies of multiple canids are being constructed. This unprecedented dataset will address the genetic underpinnings of domestication, breed formation, aging, behavior and morphological variation. More generally, this effort will advance our understanding of human and canine health.

A review on the Late Villafranchian medium-sized canid Canis arnensis based on the evidence from Poggio Rosso (Tuscany, Italy)

The fossil canid material recovered from the Early Pleistocene site of Poggio Rosso offers the opportunity to revise the taxonomical status of the Arno River dog, Canis arnensis. To date, the identification of this species is still a matter of debate due, on the one hand, to the poor state of preservation of the type specimens, and on the other hand to the lack of homogeneous descriptions and a clear diagnosis. The fossils recovered from Poggio Rosso show a good state of preservation with little (if any) plastic deformation, allowing re-evaluation of the dental and cranial characters typical of this species, as well as the proposal, for the first time, of a precise and specific diagnosis. The anatomical and morphometric features of C. arnensis exclude a close taxonomical relationship with the coeval Canis etruscus, suggesting instead a closer affinity to modern canids. The C. arnensis arrived in Italy around 1.9 Ma as the result of a dispersal event, and Poggio Rosso is the first Italian site recording the occurrence of this species. The dispersal of C. arnensis represents the arrival of the first modern canids in Europe and is therefore a significantly important biochronological event in European faunal assemblages.

<i>Nyctereutes terblanchei</i>: The raccoon dog that never was

Fossils of the raccoon dog (genus Nyctereutes) are particularly rare in the African Plio-Pleistocene record, whilst the sole living representative, Nyctereutes procyonoides, is found in eastern Asia and parts of Europe. In southern Africa, only one fossil species of raccoon dog has been identified - Nyctereutes terblanchei. N. terblanchei is recognised from a handful of Plio-Pleistocene sites in South Africa: Kromdraai, Kromdraai-Coopers and Sterkfontein in Gauteng, as well as Elandsfontein in the Western Cape Province. The validity of this species identification was questioned on the basis of the rarity of southern African fossils assigned to Nyctereutes, that is, fewer than 10 specimens have been identified as Nyctereutes. This study examined this fossil sample of the raccoon dog from the Gauteng sites and compared dental and cranial metrics of the fossil with samples of modern canids and published data. Morphological traits used to distinguish Nyctereutes, such as the pronounced subangular lobe on the mandible and the relatively large size of the lower molars, were observed to be variable in all samples. Analysis showed that the size of the dentition of the southern African fossil samples was larger than that of living raccoon dogs, but fell well within the range of that of African jackals. These results suggest that fossil Nyctereutes cannot be distinguished from other canid species based on metric data alone, and may only be diagnosable using combinations of non-metric traits of the dentition and skull. However, based on the degree of morphological variability of the traits used to diagnose Nyctereutes, as well as the rarity of this genus in the African fossil record, these fossils are more likely to belong to a species of jackal or fox.

Phylogenomics of the dog and fox family (Canidae, Carnivora) revealed by chromosome painting

Canid species (dogs and foxes) have highly rearranged karyotypes and thus represent a challenge for conventional comparative cytogenetic studies. Among them, the domestic dog is one of the best-mapped species in mammals, constituting an ideal reference genome for comparative genomic study. Here we report the results of genome-wide comparative mapping of dog chromosome-specific probes onto chromosomes of the dhole, fennec fox, and gray fox, as well as the mapping of red fox chromosome-specific probes onto chromosomes of the corsac fox. We also present an integrated comparative chromosome map between the species studied here and all canids studied previously. The integrated map demonstrates an extensive conservation of whole chromosome arms across different canid species. In addition, we have generated a comprehensive genome phylogeny for the Canidae on the basis of the chromosome rearrangements revealed by comparative painting. This genome phylogeny has provided new insights into the karyotypic relationships among the canids. Our results, together with published data, allow the formulation of a likely Canidae ancestral karyotype (CAK, 2n = 82), and reveal that at least 6-24 chromosomal fission/fusion events are needed to convert the CAK karyotype to that of the modern canids.

Were there pack-hunting canids in the Tertiary, and how can we know?

Communal hunting allows some modern canids to catch large and powerful prey. As opposed to felids, for example, Recent canids have a limited ability to grapple and subdue prey by using their forelimbs. Instead, they engage in sustained pursuit predation and the success rate during this activity typically increases with the number of individuals participating in the hunt. Clearly, such behaviors do not fossilize directly and have to be inferred from anatomy. This paper focuses on how social pack-hunting in large-bodied fossil canids can be determined and the potential for it among Tertiary canids (Canidae, Carnivora). Craniodental adaptations for handling and killing large prey and forearm utility in running and grappling are investigated by principal components and canonical variates analyses. I also test whether fossil canids responded to predation of large prey by evolving the same morphological traits as their Recent pursuit-type relatives. The analyses show that small and large members of the Recent Caninae share similar craniodental morphologies. However, the same pattern is not present in the fossil subfamilies Borophaginae and Hesperocyoninae. In the latter, large representatives are characterized by being relatively short-faced with reduced anterior premolars and enlarged posterior premolars, thus approaching a “pantherine-like” configuration. These traits are interpreted as an adaptation for killing prey with felid-like canine bites. The elbow joints of large canids also do not converge on a single morphotype. All analyzed species of borophagines and hesperocyonines have retained the ability to supinate their forearms, unlike Recent large Caninae. It is therefore likely that manual manipulation was part of their hunting behavior, thus removing an essential part of the argument for social pack-hunting in these forms, as the benefits of such a strategy become less obvious. An association between the origin of pack-pursuit “wolf avatars” and the origin and evolution of grass-dominated ecosystems is hypothesized. The results presented here clearly suggest that Recent large canids are poor ecological, morphological, and behavioral analogs for their large fossil relatives.

Estimating the body mass of Pleistocene canids: discussion of some methodological problems and a new ‘taxon free’ approach

Estimating the body mass of Pleistocene canids: discussion of some methodological problems and a new ‘taxon free’ approach

Molecular systematics of the Canidae.

Despite numerous systematic studies, the relationships among many species within the dog family, Canidae, remain unresolved. Two problems of broad evolutionary significance are the origins of the taxonomically rich canidae fauna of South America and the development in three species of the trenchant heel, a unique meat-cutting blade on the lower first molar. The first problem is of interest because the fossil record provides little evidence for the origins of divergent South American species such as the maned wolf and the bush dog. The second issue is problematic because the trenchant heel, although complex in form, may have evolved independently to assist in the processing of meat. We attempted to resolve these two issues and five other specific taxonomic controversies by phylogenetic analysis of 2,001 base pairs of mitochondrial DNA (mtDNA) sequence data from 23 canidae species. The mtDNA tree topology, coupled with data from the fossil record, and estimates of rates of DNA sequence divergence suggest at least three and possibly four North American invasions of South America. This result implies that an important chapter in the evolution of modern canids remains to be discovered in the fossil record and that the South American canidae endemism is as much the result of extinction outside of South America as it is due to speciation within South America. The origin of the trenchant heel is not well resolved by our data, although the maximum parsimony tree is weakly consistent with a single origin followed by multiple losses of the character in several extant species. A combined analysis of the mtDNA data and published morphological data provides unexpected support for a monophyletic South American canidae clade. However, the homogeneity partition tests indicate significant heterogeneity between the two data sets.

Community‐wide character displacement in Miocene hyaenas

Recent studies have found regularities in the pattern of distribution of dental parameters such as canine or carnassial length among sympatric carnivores. These regularities are taken to be indicative of community-wide character displacement. This study documents similar patterns in late Miocene and earliest Pliocene hyaenids from several localities in Eurasia and Africa. Statistical tests show ratios of lower carnassial total lengths and blade lengths between species to be suggestively equal among sympatric late Miocene hyaenas. Other measurements do not show this regular pattern. This finding mirrors that regarding modern canids in the Middle East, suggesting that a process leading to community-wide character displacement was in effect among these hyaenid taxa. Their response to this pattern suggests that they occupied a similar ecological role to modern canids. The causal basis for such a process is unknown but is suggested to lie in direct interspecific competition between carnivores rather than being a response to regularly spaced features of the environment.Character displacement, competition, Hyaenidae, Miocene, Eurasia, Africa.

Evolution of the canid brain.

Endocranial casts of 12 genera of extinctcanids, covering a time span of 30 million years, and of all living canid genera provide information on brain evolution in that carnivoran family. The oldest canid brains had only suprasylvian and coronolateral sulci, a widely exposed cerebellum with a straight posterior vermis, a high rhinal fissure and a strikingly undeveloped frontal lobe. By 25 million years ago, ectosylvian, ectolateral and presylvian sulci had appeared, and by about 12 million years ago, a Sylvian sulcus had developed, expansion of the temporal lobe and of orbital and sigmoid gyri was noticeable, and lobule VII of the cerebellar vermis had enlarged and twisted in the line leading to modern canids. Ansate, postcruciate and cruciate sulci developed along with the expansion of the sigmoid gyri. Canid brains 15–30 million years old average slightly smaller relative to body size than do modern canid brains, while later fossil canid brains are about the same relative size as modern ones. Modern canid brains are relatively uniform in external morphology, differing mainly in the relative size of the prorean gyrus.

Evolution of the Canid Brain; pp. 186–202

Endocranial casts of 12 genera of extinctcanids, covering a time span of 30 million years, and of all living canid genera provide information on brain evolution in that carnivoran family. The oldest canid brains had only suprasylvian and coronolateral sulci, a widely exposed cerebellum with a straight posterior vermis, a high rhinal fissure and a strikingly undeveloped frontal lobe. By 25 million years ago, ectosylvian, ectolateral and presylvian sulci had appeared, and by about 12 million years ago, a Sylvian sulcus had developed, expansion of the temporal lobe and of orbital and sigmoid gyri was noticeable, and lobule VII of the cerebellar vermis had enlarged and twisted in the line leading to modern canids. Ansate, postcruciate and cruciate sulci developed along with the expansion of the sigmoid gyri. Canid brains 15–30 million years old average slightly smaller relative to body size than do modern canid brains, while later fossil canid brains are about the same relative size as modern ones. Modern canid brains are relatively uniform in external morphology, differing mainly in the relative size of the prorean gyrus.