Topic
Genus Equus
About: Genus Equus is a research topic. Over the lifetime, 68 publications have been published within this topic receiving 3001 citations.
Papers published on a yearly basis
Papers
University of Copenhagen1, University of Alberta2, University of California, Santa Cruz3, Technical University of Denmark4, University of Chicago5, University of Bristol6, University of California, Berkeley7, Macau University of Science and Technology8, University of Texas at Austin9, University of Southampton10, Norwegian University of Life Sciences11, Centre national de la recherche scientifique12, Uppsala University13, Cornell University14, Copenhagen Zoo15, King Saud University16, University of York17
TL;DR: Thealyses suggest that the Equus lineage giving rise to all contemporary horses, zebras and donkeys originated 4.0–4.5 million years before present, twice the conventionally accepted time to the most recent common ancestor of the genus Equus, and supports the contention that Przewalski's horses represent the last surviving wild horse population.
Abstract: The rich fossil record of equids has made them a model for evolutionary processes. Here we present a 1.12-times coverage draft genome from a horse bone recovered from permafrost dated to approximately 560-780 thousand years before present (kyr BP). Our data represent the oldest full genome sequence determined so far by almost an order of magnitude. For comparison, we sequenced the genome of a Late Pleistocene horse (43 kyr BP), and modern genomes of five domestic horse breeds (Equus ferus caballus), a Przewalski's horse (E. f. przewalskii) and a donkey (E. asinus). Our analyses suggest that the Equus lineage giving rise to all contemporary horses, zebras and donkeys originated 4.0-4.5 million years before present (Myr BP), twice the conventionally accepted time to the most recent common ancestor of the genus Equus. We also find that horse population size fluctuated multiple times over the past 2 Myr, particularly during periods of severe climatic changes. We estimate that the Przewalski's and domestic horse populations diverged 38-72 kyr BP, and find no evidence of recent admixture between the domestic horse breeds and the Przewalski's horse investigated. This supports the contention that Przewalski's horses represent the last surviving wild horse population. We find similar levels of genetic variation among Przewalski's and domestic populations, indicating that the former are genetically viable and worthy of conservation efforts. We also find evidence for continuous selection on the immune system and olfaction throughout horse evolution. Finally, we identify 29 genomic regions among horse breeds that deviate from neutrality and show low levels of genetic variation compared to the Przewalski's horse. Such regions could correspond to loci selected early during domestication.
841 citations
TL;DR: Dried muscle from a museum specimen of the quagga, a zebra-like species that became extinct in 1883, is examined, and DNA was extracted in amounts approaching 1% of that expected from fresh muscle, and that the DNA was of relatively low molecular weight.
Abstract: To determine whether DNA survives and can be recovered from the remains of extinct creatures, we have examined dried muscle from a museum specimen of the quagga, a zebra-like species (Equus quagga) that became extinct in 1883 (ref. 1). We report that DNA was extracted from this tissue in amounts approaching 1% of that expected from fresh muscle, and that the DNA was of relatively low molecular weight. Among the many clones obtained from the quagga DNA, two containing pieces of mitochondrial DNA (mtDNA) were sequenced. These sequences, comprising 229 nucleotide pairs, differ by 12 base substitutions from the corresponding sequences of mtDNA from a mountain zebra, an extant member of the genus Equus. The number, nature and locations of the substitutions imply that there has been little or no postmortem modification of the quagga DNA sequences, and that the two species had a common ancestor 3-4 Myr ago, consistent with fossil evidence concerning the age of the genus Equus.
773 citations
TL;DR: In this paper, it was shown that there were at least three major dispersal events of large mammals during the Pliocene (at 1.9, 2.6 and 3.7 Myr).
Abstract: The Cenozoic history of land mammals is marked by brief periods of intercontinental dispersal, termed dispersal events1,2. One of these dispersal events includes the horse Equus, that evolved in North America, dispersed to the Old World in the Pliocene, and became a prominent member of Old World Pleistocene communities. Equus was derived from a species of the single-toed horse Pliohippus, known only from North America3. Timing for the Pliocene dispersal of Equus into Europe was questioned4 following resolution for the appearance of Equus into the Siwalik sequence of Pakistan5. It seems that there were at least three major dispersal events of large mammals during the Pliocene (at 1.9, 2.6 and 3.7 Myr). We now report new data that limit the time of Equus' dispersal and into Europe to the 2.6 Myr dispersal event.
199 citations
TL;DR: The variation between species supports a divergence of extant lineages from a common ancestor approximately 3.9 Myr before the present, and trees constructed according to the parsimony principle indicate that the three extant zebra species represent a monophyletic group.
Abstract: Employing mitochondrial DNA (mtDNA) restriction-endonuclease maps as the basis of comparison, we have investigated the evolutionary affinities of the seven species generally recognized as the genus Equus. Individual species' cleavage maps contained an average of 60 cleavage sites for 16 enzymes, of which 29 were invariant for all species. Based on an average divergence rate of 2%/Myr, the variation between species supports a divergence of extant lineages from a common ancestor approximately 3.9 Myr before the present. Comparisons of cleavage maps between Equus przewalskii (Mongolian wild horse) and E. caballus (domestic horse) yielded estimates of nucleotide sequence divergence ranging from 0.27% to 0.41%. This range was due to intraspecific variation, which was noted only for E. caballus. For pairwise comparisons within this family, estimates of sequence divergence ranged from 0% (E. hemionus onager vs. E. h. kulan) to 7.8% (E. przewalskii vs. E. h. onager). Trees constructed according to the parsimony principle, on the basis of 31 phylogenetically informative restriction sites, indicate that the three extant zebra species represent a monophyletic group with E. grevyi and E. burchelli antiquorum diverging most recently. The phylogenetic relationships of E. africanus and E. hemionus remain enigmatic on the basis of the mtDNA analysis, although a recent divergence is unsupported.
111 citations
TL;DR: The phylogenetic reconstruction ofcentromere repositioning events demonstrates that the acquisition of satellite DNA occurs after the formation of the centromere during evolution and that centromeres can function over millions of years and many generations without detectable satellite DNA.
Abstract: In a previous study, we showed that centromere repositioning, that is the shift along the chromosome of the centromeric function without DNA sequence rearrangement, has occurred frequently during the evolution of the genus Equus. In this work, the analysis of the chromosomal distribution of satellite tandem repeats in Equus caballus, E. asinus, E. grevyi, and E. burchelli highlighted two atypical features: 1) several centromeres, including the previously described evolutionary new centromeres (ENCs), seem to be devoid of satellite DNA, and 2) satellite repeats are often present at non-centromeric termini, probably corresponding to relics of ancestral now inactive centromeres. Immuno-FISH experiments using satellite DNA and antibodies against the kinetochore protein CENP-A demonstrated that satellite-less primary constrictions are actually endowed with centromeric function. The phylogenetic reconstruction of centromere repositioning events demonstrates that the acquisition of satellite DNA occurs after the formation of the centromere during evolution and that centromeres can function over millions of years and many generations without detectable satellite DNA. The rapidly evolving Equus species gave us the opportunity to identify different intermediate steps along the full maturation of ENCs.
103 citations
Related Topics (5)
Performance Metrics
| Year | Papers |
|---|---|
| 2022 | 1 |
| 2021 | 5 |
| 2020 | 3 |
| 2019 | 4 |
| 2018 | 2 |
| 2017 | 5 |