Topic:Evolutionary Biology
Evolutionary biology and horses focus on the study of the evolutionary processes that have shaped the development, adaptation, and diversification of the Equus genus. This field examines the genetic, morphological, and ecological changes that have occurred over millions of years, leading to the modern horse. Researchers explore the transition from small, multi-toed ancestors to the large, single-toed horses of today, analyzing fossil records, genetic data, and environmental factors that influenced these changes. This page compiles peer-reviewed research studies and scholarly articles that investigate the evolutionary history, genetic adaptations, and ecological interactions of horses, providing insights into their development and survival strategies throughout history.
Mammalian male mutation bias: impacts of generation time and regional variation in substitution rates. In mammals, males undergo a greater number of germline cell divisions compared with females. Thus, the male germline accumulates more DNA replication errors, which result in male mutation bias-a higher mutation rate for males than for females. The phenomenon of male mutation bias has been investigated mostly for rodents and primates, however, it has not been studied in detail for other mammalian orders. Here we sequenced and analyzed five introns of three genes (DBX/DBY, UTX/UTY, and ZFX/ZFY) homologous between X and Y chromosomes in several species of perissodactyls (horses and rhinos) and of...
High-resolution gene maps of horse chromosomes 14 and 21: additional insights into evolution and rearrangements of HSA5 homologs in mammals. High-resolution physically ordered gene maps for equine homologs of human chromosome 5 (HSA5), viz., horse chromosomes 14 and 21 (ECA14 and ECA21), were generated by adding 179 new loci (131 gene-specific and 48 microsatellites) to the existing maps of the two chromosomes. The loci were mapped primarily by genotyping on a 5000-rad horse x hamster radiation hybrid panel, of which 28 were mapped by fluorescence in situ hybridization. The approximately fivefold increase in the number of mapped markers on the two chromosomes improves the average resolution of the map to 1 marker/0.9 Mb. The improv...
Development of the Lipizzan horse breed. The development and a brief history of the Lipizzan horse breed are reviewed. The contribution of several breeds, some of them already extinct, to the development of the Lipizzan horse, gives it a special status representing an important gene pool. This well-documented breed is a part of the common European natural and cultural heritage. Breeding practices establishing stallion and mare family lines as well as availability of pedigrees are described. Molecular analysis of mitochondrial DNA (mtDNA) and microsatellite data allowed us to analyse the structure of the Lipizzan population, to estima...
Highly diverse type of equine arteritis virus (EAV) from the semen of a South African donkey: short communication. Equine arteritis virus (EAV) was detected by RT-nested PCR in semen samples from a naturally infected South African donkey. Sequence analysis of the amplified ORF5 fragment revealed only 60 to 70% nucleotide identity to a panel of EAV reference sequences. The unique donkey EAV sequence was also found to be stable during passage in horses. The sequence data reported in this study indicate that the South African donkey variant might represent a new genotype of EAV. The distinct genetic properties of the South African asinine strain of EAV suggest a divergent evolution of this arterivirus in vari...
Morphological evolution and heritability estimates for some biometric traits in the Murgese horse breed. A data set concerning 1,816 subjects entered in the Italian Horse Registry from 1925 to 2002 was analyzed to investigate the morphological evolution of the Murgese horse and to obtain useful elements to enhance breeding practices. Three basic body measurements (height at withers, chest girth, and cannon bone circumference) were considered for each subject. Heritabilities were calculated for each parameter to infer the growth and development traits of this breed. Over the past 20 years the Murgese horse has undergone considerable changes, passing from a typical mesomorphic structure (height at ...
A comparative kinetic analysis of the reactivity of plant, horse, and human respiratory cytochrome c towards cytochrome c oxidase. Two synthetic genes coding for human and Arabidopsis cytochrome c, respectively, have been designed and constructed, and the recombinant proteins have been over-expressed in Escherichia coli cells. Thus a comparative analysis of the two heme proteins, including horse cytochrome c as a reference, has been performed. In addition to their physico-chemical properties, the redox behavior of the three proteins has been analyzed by following the kinetics of both their reduction by flavin semiquinones (lumiflavin, riboflavin, and FMN) and oxidation by cytochrome c oxidase. The resulting data indicate ...
Adaptive value of ambling gaits in primates and other mammals. At speeds between the walk and the gallop, most mammals trot. Primates almost never trot, and it has been claimed that they transition directly from a walk to a gallop without any distinctive mid-speed running gait. If true, this would be another characteristic difference between the locomotion of primates and that of most other quadrupedal mammals. Presently, however, few data exist concerning the actual presence or absence of intermediate-speed gaits (i.e. gaits that are used between a walk and a gallop) in primates. Video records of running in twelve primate species reveal that, unlike most...
On the Pleistocene extinctions of Alaskan mammoths and horses. The fossil record has been used to shed light on the late Pleistocene megafaunal extinctions in North America and elsewhere. It is therefore important to account for variability due to the incompleteness of the fossil record and error in dating fossil remains. Here, a joint confidence region for the extinction times of horses and mammoths in Alaska is constructed. The results suggest that a prior claim that the extinction of horses preceded the arrival of humans cannot be made with confidence.
Sequence analysis of a 212 kb defensin gene cluster on ECA 27q17. Defensins are a family of evolutionary ancient antimicrobial peptides consisting of three sub-families: alpha-, beta- and theta-defensins. This investigation was focused on the genomic characterization of equine beta-defensins and the investigation of the potential clustering of beta-defensin genes in the equine genome. Six genomic BAC clones were isolated from the CHORI-241 library and one of these was mapped by FISH to ECA 27q17. This location was confirmed by RH-mapping. The contiguous 212 kb sequence of this clone was determined. Sequence analysis revealed the identification of ten pseudog...
Construction of a medium-density horse gene map. A medium-density map of the horse genome (Equus caballus) was constructed using genes evenly distributed over the human genome. Three hundred and twenty-three exonic primer pairs were used to screen the INRA and the CHORI-241 equine BAC libraries by polymerase chain reaction and by filter hybridization respectively. Two hundred and thirty-seven BACs containing equine gene orthologues, confirmed by sequencing, were isolated. The BACs were localized to horse chromosomes by fluorescent in situ hybridization (FISH). Overall, 165 genes were assigned to the equine genomic map by radiation hybrid (RH...
Iberian origins of New World horse breeds. Fossil records, archaeological proofs, and historical documents report that horses persisted continuously in the Iberian Peninsula since the Pleistocene and were taken to the American continent (New World) in the 15th century. To investigate the variation within the mitochondrial DNA (mtDNA) control region of Iberian and New World horse breeds, to analyze their relationships, and to test the historical origin of New World horses, a total of 153 samples, representing 30 Iberian and New World breeds, were analyzed by sequencing mtDNA control region fragments. Fifty-four haplotypes were found and...
Evidence of an oscillating peripheral clock in an equine fibroblast cell line and adipose tissue but not in peripheral blood. The master mammalian pacemaker in the brain controls numerous diverse physiological and behavioral processes throughout the organism. Timing information is continually transmitted from the master clock to peripheral organs to synchronize rhythmic daily oscillations of clock gene transcripts and control local physiology. To investigate the presence of peripheral clocks in the horse, quantitative real-time RT-PCR assays were designed to detect levels of equine clock genes. Expression profiles for Per2, Bmal1 and Cry1 were first determined in a synchronized equine cell line. Subsequently, express...
Evolutionary movement of centromeres in horse, donkey, and zebra. Centromere repositioning (CR) is a recently discovered biological phenomenon consisting of the emergence of a new centromere along a chromosome and the inactivation of the old one. After a CR, the primary constriction and the centromeric function are localized in a new position while the order of physical markers on the chromosome remains unchanged. These events profoundly affect chromosomal architecture. Since horses, asses, and zebras, whose evolutionary divergence is relatively recent, show remarkable morphological similarity and capacity to interbreed despite their chromosomes differing co...
Genetic diversity within and among four South European native horse breeds based on microsatellite DNA analysis: implications for conservation. In the present study, genetic analyses of diversity and differentiation were performed on four Basque-Navarrese semiferal native horse breeds. In total, 417 animals were genotyped for 12 microsatellite markers. Mean heterozygosity was higher than in other horse breeds, surely as a consequence of management. Although the population size of some of these breeds has declined appreciably in the past century, no genetic bottleneck was detected in any of the breeds, possibly because it was not narrow enough to be detectable. In the phylogenetic tree, the Jaca Navarra breed was very similar to the Po...
The origins of Iberian horses assessed via mitochondrial DNA. Despite a number of recent studies that have focused on the origin of domestic horses, genetic relationships between major geographical clusters still remain poorly understood. In this study we analyzed a 296 bp mtDNA fragment from the HVI region of 171 horses representing 11 native Iberian, Barb, and Exmoor breeds to assess the maternal phylogeography of Iberian horses. The mtDNA haplogroup with a CCG motif (nucleotide position 15,494 to 15,496) was the most frequent in Iberian and Barb breeds (0.42 and 0.57, respectively), regardless of geographic location or group of breeds. This finding su...
Genetic structure of an endangered Portuguese semiferal pony breed, the Garrano. The present study intends to survey the genetic variability of an endangered semiferal Portuguese native pony breed, the Garrano. Thirteen microsatellite markers were examined in 277 animals born in 1998, belonging to eight subpopulations corresponding to eight northern Portuguese geographic regions. Mean heterozygosity (H(o)) in the Garrano breed was 0.732, ranging from 0.531 to 0.857 across subpopulations. Allelic frequencies and diversity differed significantly between regions, suggesting the existence of genetic differentiation within the breed confirmed by the population differentiation e...
A high-resolution physical map of equine homologs of HSA19 shows divergent evolution compared with other mammals. A high-resolution (1 marker/700 kb) physically ordered radiation hybrid (RH) and comparative map of 122 loci on equine homologs of human Chromosome 19 (HSA19) shows a variant evolution of these segments in equids/Perissodactyls compared with other mammals. The segments include parts of both the long and the short arm of horse Chromosome 7 (ECA7), the proximal part of ECA21, and the entire short arm of ECA10. The map includes 93 new markers, of which 89 (64 gene-specific and 25 microsatellite) were genotyped on a 5000-rad horse x hamster RH panel, and 4 were mapped exclusively by FISH. The orie...
Nucleotide sequence of complementary DNA encoding for quaking protein of cow, horse and pig. Complementary DNA (cDNA) for bovine quaking gene (Bqk), equine quaking gene (Eqk) and porcine quaking gene (Pqk), which are homologous to mouse quaking gene (qkI), were isolated, and their nucleotide sequences were determined. cDNA sequences of Bqk, Eqk and Pqk showed very high homology to that of qkI at nucleotide level; 94.2, 95.7 and 95.6%, respectively. Deduced amino acid sequences for Bqk, Eqk and Pqk perfectly matched to that of qkI. These findings suggest that the quaking gene family is highly conserved during mammalian evolution, and that Bqk, Eqk and Pqk are likely to have important b...
Comparative chromosomal studies of E. caballus (ECA) and E. przewalskii (EPR) in a female F1 hybrid. Previous research revealed that the karyotypes of Equus przewalskii (2n = 66) and Equus caballus (2n = 64) differ by one pair of metacentric chromosomes, present in ECA but not in EPR, and two pairs of acrocentric chromosomes found only in the EPR karyotype. The formation of a trivalent during meiosis in a male F1 hybrid and the homologies in G-banding patterns suggest that ECA 5 corresponds to two acrocentric EPR chromosomes resulting from a Robertsonian fusion or fission event. Chromosomal investigations of a female interspecies F1 hybrid including banded karyograms and fluorescence in situ ...
Equine FISH mapping of 36 genes known to locate on human chromosome ends. The INRA and the CHORI-241 horse BAC libraries were screened by hybridization with DNA probes and/or directly by PCR with primers designed in consensus sequences of genes localized at the end of each human chromosome. BAC clones were retrieved and 36 could be FISH mapped after the expected gene was confirmed in each BAC by sequencing. Our results show that 16 BACs can be considered to be at telomeric or centromeric positions in the horse and 15 were found at the boundary of actually defined conserved segments even-though often located within conserved syntenic fragments between horse and human...
Evolution, systematics, and phylogeography of pleistocene horses in the new world: a molecular perspective. The rich fossil record of horses has made them a classic example of evolutionary processes. However, while the overall picture of equid evolution is well known, the details are surprisingly poorly understood, especially for the later Pliocene and Pleistocene, c. 3 million to 0.01 million years (Ma) ago, and nowhere more so than in the Americas. There is no consensus on the number of equid species or even the number of lineages that existed in these continents. Likewise, the origin of the endemic South American genus Hippidion is unresolved, as is the phylogenetic position of the "stilt-legged"...
The Lusitano horse maternal lineage based on mitochondrial D-loop sequence variation. The analysis of mitochondrial D-loop sequences (408 bp) from 145 Lusitano founder mares yielded a total of 27 different haplotypes. The distribution of these mtDNA sequences was quite unequal, with the three most frequent ones representing 56.5% of all the Lusitano founder mares and 14 haplotypes (51.9%) being rare variants found only once in the sampling. Four main haplotype clusters were present in the Lusitano breed. The comparison of these sequences with other equine haplotypes shows that they fall in groups shared with other horse breeds. These data support the hypothesis of multiple dome...
Mitochondrial DNA analysis of horses recovered from a frozen tomb (Berel site, Kazakhstan, 3rd Century BC). Sequence polymorphism of the mitochondrial DNA D-loop was used to determine the genetic diversity of horses recovered from a Scythian princely tomb dating from the beginning of the 3rd century BC. Eight haplotypes were found among the 13 ancient horse samples tested. Phylogenetical analysis showed that these ancient horse's sequences, along with two Yakut ones, were distributed throughout the tree defined by modern horses' sequences and are closely related to them. No clear geographical affiliation of the specimens studied was thus determined. Our work, among others, supports the very ancient ...
[Molecular genetic studies of the “Einsiedler” horse population]. In this study it was investigated whether the "Einsiedler" warmblood horse, a historically old horse population from central Switzerland (Abbey of Einsiedeln), is distinguishable from micellaneous horse breeds, using molecular genetic techniques. The breeding history of Einsiedler horses is characterised by systematic line breeding through the dams. Therefore, two Einsiedler dam lines (N = 28), going back to the middle of the 19th century according to pedigree entries, were the focus of the survey. Random samples of diverse warmblood horse populations, but also samples from more distinct types...
Evolution of the equine infectious anemia virus long terminal repeat during the alteration of cell tropism. Equine infectious anemia virus (EIAV) is a lentivirus with in vivo cell tropism primarily for tissue macrophages; however, in vitro the virus can be adapted to fibroblasts and other cell types. Tropism adaptation is associated with both envelope and long terminal repeat (LTR) changes, and findings strongly suggest that these regions of the genome influence cell tropism and virulence. Furthermore, high levels of genetic variation have been well documented in both of these genomic regions. However, specific EIAV nucleotide or amino acid changes that are responsible for cell tropism changes have ...
High-resolution RH map of horse chromosome 22 reveals a putative ancestral vertebrate chromosome. High-resolution gene maps of individual equine chromosomes are essential to identify genes governing traits of economic importance in the horse. In pursuit of this goal we herein report the generation of a dense map of horse chromosome 22 (ECA22) comprising 83 markers, of which 52 represent specific genes and 31 are microsatellites. The map spans 831 cR over an estimated 64 Mb of physical length of the chromosome, thus providing markers at approximately 770 kb or 10 cR intervals. Overall, the resolution of the map is to date the densest in the horse and is the highest for any of the domesticat...