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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.
What fossils can tell us about the evolution of viviparity and placentation.
Placenta    September 6, 2008   Volume 29, Issue 11 930-931 doi: 10.1016/j.placenta.2008.07.012
Carter AM.Recently a fossil of one of the earliest jawed fishes was found with a fetal skeleton and the remains of a cord. It was from the Devonian period and takes the history of vertebrate placentation back to 380 million years ago. This and later fossil evidence for viviparity in marine reptiles and early mammals is reviewed. Of particular interest are the fossils of horses as they document that a reproductive strategy with a single precocial newborn was evolved early on. In one instance there is sufficient representation of soft tissue to imply that early horses had a diffuse placenta, much as had b...
Preliminary investigation of morphological differences between ten breeds of horses suggests selection for paedomorphosis.
Journal of applied animal welfare science : JAAWS    June 24, 2008   Volume 11, Issue 3 204-212 doi: 10.1080/10888700802100918
Goodwin D, Levine M, McGreevy PD.Paedomorphosis is the retention of juvenile morphology at maturity and is important in generating evolutionary change in domestic species and species in the wild. When comparing dogs with the wolf, this preliminary study saw paedomorphosis in their physical and behavioral traits (Goodwin, Bradshaw, & Wickens, 1997). This preliminary study compared morphological characteristics of 10 breeds from northern regions (Shetland ponies) and southern regions (Arabians) with the Exmoor pony. Twenty-three respondents from the United Kingdom and Australia rated the breeds for 7 physical traits. As evi...
The horse pseudoautosomal region (PAR): characterization and comparison with the human, chimp and mouse PARs.
Cytogenetic and genome research    June 9, 2008   Volume 121, Issue 2 102-109 doi: 10.1159/000125835
Raudsepp T, Chowdhary BP.The pseudoautosomal region (PAR) is a genomic segment on mammalian sex chromosomes where sequence homology mimics that seen between autosomal homologues. The region is essential for pairing and proper segregation of sex chromosomes during male meiosis. As yet, only human/chimp and mouse PARs have been characterized. The two groups of species differ dramatically in gene content and size of the PAR and therefore do not provide clues about the likely evolution and constitution of PAR among mammals. Here we characterize the equine PAR by i) isolating and arranging 71 BACs containing 129 markers (1...
The cloned equine thyrotropin receptor is hypersensitive to human chorionic gonadotropin; identification of three residues in the extracellular domain involved in ligand specificity.
Endocrinology    June 5, 2008   Volume 149, Issue 10 5088-5096 doi: 10.1210/en.2008-0423
Royer J, Lefevre-Minisini A, Caltabiano G, Lacombe T, Malthiery Y, Savagner F, Pardo L, Rodien P.The receptors for TSH, LH/chorionic gonadotropin (CG), and FSH belong to the same subfamily of G protein-coupled receptors. The specificity of recognition of their cognate hormone involves a limited number of residues in the leucine-rich repeats present in the N-terminal ectodomain of the receptor. It is admitted that receptors of this subfamily coevoluted with their respective ligands. The secretion of CG is restricted to gestation of primates and Equidae. We hypothesized that, facing the challenge of a new hormone, the glycoprotein hormone receptors would have evolved differently in Equidae ...
Concerted evolution of vertebrate CCR2 and CCR5 genes and the origin of a recombinant equine CCR5/2 gene.
The Journal of heredity    May 22, 2008   Volume 99, Issue 5 500-511 doi: 10.1093/jhered/esn029
Perelygin AA, Zharkikh AA, Astakhova NM, Lear TL, Brinton MA.Chemokine receptors (CCRs) play an essential role in the initiation of an innate immune host response. Several of these receptors have been shown to modulate the outcome of viral infections. The recent availability of complete genome sequences from a number of species provides a unique opportunity to analyze the evolution of the CCR genes. A phylogenetic analysis revealed that the CCR2 gene evolved in concert with the paralogous CCR5 gene, but not with another paralogous gene, CCR3, in the opossum, platypus, rabbit, guinea pig, cat, and rodent lineages. In addition, evidence of concerted evolu...
Ancient DNA clarifies the evolutionary history of American Late Pleistocene equids.
Journal of molecular evolution    April 9, 2008   Volume 66, Issue 5 533-538 doi: 10.1007/s00239-008-9100-x
Orlando L, Male D, Alberdi MT, Prado JL, Prieto A, Cooper A, Hänni C.Hippidions are past members of the equid lineage which appeared in the South American fossil record around 2.5 Ma but then became extinct during the great late Pleistocene megafaunal extinction. According to fossil records and numerous dental, cranial, and postcranial characters, Hippidion and Equus lineages were expected to cluster in two distinct phylogenetic groups that diverged at least 10 MY, long before the emergence of the first Equus. However, the first DNA sequence information retrieved from Hippidion fossils supported a striking different phylogeny, with hippidions nesting inside a p...
Multidirectional cross-species painting illuminates the history of karyotypic evolution in Perissodactyla.
Chromosome research : an international journal on the molecular, supramolecular and evolutionary aspects of chromosome biology    February 23, 2008   Volume 16, Issue 1 89-107 doi: 10.1007/s10577-007-1201-7
Trifonov VA, Stanyon R, Nesterenko AI, Fu B, Perelman PL, O'Brien PC, Stone G, Rubtsova NV, Houck ML, Robinson TJ, Ferguson-Smith MA, Dobigny G....The order Perissodactyla, the group of odd-toed ungulates, includes three extant families: Equidae, Tapiridae, and Rhinocerotidae. The extremely rapid karyotypic diversification in perissodactyls has so far prevented the establishment of genome-wide homology maps between these three families by traditional cytogenetic approaches. Here we report the first genome-wide comparative chromosome maps of African rhinoceroses, four tapir species, four equine species, and humans. These maps were established by multidirectional chromosome painting, with paint probes derived from flow-sorted chromosomes o...
A chromosome inversion near the KIT gene and the Tobiano spotting pattern in horses.
Cytogenetic and genome research    February 1, 2008   Volume 119, Issue 3-4 225-230 doi: 10.1159/000112065
Brooks SA, Lear TL, Adelson DL, Bailey E.Tobiano is a white spotting pattern in horses caused by a dominant gene, Tobiano(TO). Here, we report TO associated with a large paracentric chromosome inversion on horse chromosome 3. DNA sequences flanking the inversion were identified and a PCR test was developed to detect the inversion. The inversion was only found in horses with the tobiano pattern, including horses with diverse genetic backgrounds, which indicated a common genetic origin thousands of years ago. The inversion does not interrupt any annotated genes, but begins approximately 100 kb downstream of the KIT gene. This inversion...
Male infanticide and paternity analyses in a socially natural herd of Przewalski’s horses: sexual selection?
Behavioural processes    January 12, 2008   Volume 78, Issue 3 335-339 doi: 10.1016/j.beproc.2007.12.009
Feh C, Munkhtuya B.The sexual selection hypothesis explains infanticide by males in many mammals. In our 11-year study, we investigated this hypothesis in a herd of Przewalski's horses where we had witnessed infanticidal attacks. Infanticide was highly conditional and not simply linked to takeovers. Attacks occurred in only five of 39 cases following a takeover, and DNA paternity revealed that, although infanticidal stallions were not the genetic fathers in four cases out of five, stallions present at birth did not significantly attempt to kill unrelated foals. Infanticide did not reduce birth intervals; only in...
Genetic diversity in a feral horse population from Sable Island, Canada.
The Journal of heredity    September 13, 2007   Volume 98, Issue 6 594-602 doi: 10.1093/jhered/esm064
Plante Y, Vega-Pla JL, Lucas Z, Colling D, de March B, Buchanan F.The present-day Sable Island horse population, inhabiting an island off the eastern coast of Canada, is believed to have originated mainly from horses confiscated from the early French settlers in Nova Scotia in the latter half of the 18th century. In 1960, the Sable Island horses were given legal protected status and no human interference has since been allowed. The objective of this study was to characterize the current genetic diversity in Sable Island horses in comparison to 15 other horse breeds commonly found in Canada and 5 Spanish breeds. A total of 145 alleles from 12 microsatellite l...
Karyotypic relationships among Equus grevyi, Equus burchelli and domestic horse defined using horse chromosome arm-specific probes.
Chromosome research : an international journal on the molecular, supramolecular and evolutionary aspects of chromosome biology    August 23, 2007   Volume 15, Issue 6 807-813 doi: 10.1007/s10577-007-1164-8
Musilova P, Kubickova S, Zrnova E, Horin P, Vahala J, Rubes J.Using laser microdissection we prepared a set of horse chromosome arm-specific probes. Most of the probes were generated from horse chromosomes, some of them were derived from Equus zebra hartmannae. The set of probes were hybridized onto E. grevyi chromosomes in order to establish a genome-wide chromosomal correspondence between this zebra and horse. The use of arm-specific probes provided us with more information on the mutual arrangement of the genomes than we could obtain by means of whole-chromosome paints generated by flow sorting, even if we used reciprocal painting with probe sets from...
High altitude adaptation and phylogenetic analysis of Tibetan horse based on the mitochondrial genome.
Journal of genetics and genomics = Yi chuan xue bao    August 21, 2007   Volume 34, Issue 8 720-729 doi: 10.1016/S1673-8527(07)60081-2
Xu S, Luosang J, Hua S, He J, Ciren A, Wang W, Tong X, Liang Y, Wang J, Zheng X.To investigate genetic mechanisms of high altitude adaptations of animals living in the Tibetan Plateau, three mitochondrial genomes (mt-genome) of Tibetan horses living in Naqu (4,500 m) of Tibetan, Zhongdian (3,300 m) and Deqin (3,100 m) of Yunnan province were sequenced. The structures and lengths of these three mt-genomes are similar to the Cheju horse, which is related to Tibetan horses, but little shorter than the Swedish horse. The pair-wise identity of these three horses on nucleotide level is more than 99.3%. When the gene encoding the mitochondrial protein of Tibetan horses was analy...
Restoring America’s big, wild animals.
Scientific American    August 1, 2007   Volume 296, Issue 6 70-77 doi: 10.1038/scientificamerican0607-70
Donlan CJ.No abstract available
Phylogenetic relationships of German heavy draught horse breeds inferred from mitochondrial DNA D-loop variation.
Journal of animal breeding and genetics = Zeitschrift fur Tierzuchtung und Zuchtungsbiologie    May 10, 2007   Volume 124, Issue 2 94-100 doi: 10.1111/j.1439-0388.2007.00636.x
Aberle KS, Hamann H, Drögemüller C, Distl O.We analysed a 610-bp mitochondrial (mt)DNA D-loop fragment in a sample of German draught horse breeds and compared the polymorphic sites with sequences from Arabian, Hanoverian, Exmoor, Icelandic, Sorraia and Przewalski's Horses as well as with Suffolk, Shire and Belgian horses. In a total of 65 horses, 70 polymorphic sites representing 47 haplotypes were observed. The average percentage of polymorphic sites was 11.5% for the mtDNA fragment analysed. In the nine different draught horse breeds including South German, Mecklenburg, Saxon Thuringa coldblood, Rhenisch German, Schleswig Draught Hors...
Posture, gait and the ecological relevance of locomotor costs and energy-saving mechanisms in tetrapods.
Zoology (Jena, Germany)    May 7, 2007   Volume 110, Issue 4 271-289 doi: 10.1016/j.zool.2007.01.003
Reilly SM, McElroy EJ, Biknevicius AR.A reanalysis of locomotor data from functional, energetic, mechanical and ecological perspectives reveals that limb posture has major effects on limb biomechanics, energy-saving mechanisms and the costs of locomotion. Regressions of data coded by posture (crouched vs. erect) reveal nonlinear patterns in metabolic cost, limb muscle mass, effective mechanical advantage, and stride characteristics. In small crouched animals energy savings from spring and pendular mechanisms are inconsequential and thus the metabolic cost of locomotion is driven by muscle activation costs. Stride frequency appears...
Susceptibility of mammalian deoxyribonucleases I (DNases I) to proteolysis by proteases and its relationships to tissue distribution: biochemical and molecular analysis of equine DNase I.
Comparative biochemistry and physiology. Part B, Biochemistry & molecular biology    May 5, 2007   Volume 148, Issue 1 93-102 doi: 10.1016/j.cbpb.2007.04.018
Ueki M, Takeshita H, Fujihara J, Ueta G, Nakajima T, Kominato Y, Kishi K, Iida R, Yasuda T.Equine (Equus caballus) deoxyribonuclease I (DNase I) was purified from the parotid gland, and its 1295-bp cDNA was cloned. The mature equine DNase I protein consisted of 260 amino acid residues. The enzymatic properties and structural aspects of the equine enzyme were closely similar to those of other mammalian DNases I. Mammalian DNases I are classified into three types--pancreatic, parotid and pancreatic-parotid-based on their tissue distribution; as equine DNase I showed the highest activity in the parotid gland, it was confirmed to be of the parotid-type. Comparison of the susceptibility ...
Genetic characterization of Zanskari breed of horse.
Journal of genetics    April 5, 2007   Volume 85, Issue 3 199-203 doi: 10.1007/BF02935331
Behl R, Behl J, Gupta N, Gupta SC, Ahlawat SP, Ragnekar M, Ahmed Z.No abstract available
Can studies of cognitive abilities and of life in the wild really help us to understand equine learning?
Behavioural processes    March 6, 2007   Volume 76, Issue 1 49-60 doi: 10.1016/j.beproc.2006.11.009
Leblanc MA, Duncan P.No abstract available
Equine learning behaviour: the importance of evolutionary and ecological approach in research.
Behavioural processes    March 6, 2007   Volume 76, Issue 1 40-60 doi: 10.1016/j.beproc.2006.09.019
Sigurjónsdóttir H.No abstract available
Induction of pulsatile secretion of leptin in horses following thyroidectomy.
The Journal of endocrinology    February 7, 2007   Volume 192, Issue 2 353-359 doi: 10.1677/joe.1.06989
Buff PR, Messer NT, Cogswell AM, Wilson DA, Johnson PJ, Keisler DH, Ganjam VK.Endocrine characteristics of Quarter Horse-type mares were determined during a 68 h feed deprivation and again in the same mares following surgical thyroidectomy (THX). A crossover experimental design was implemented, in which mares received brome hay available ad libitum (FED) or were food deprived (RES) for 68 h. Blood samples were collected every 20 min for 48 h, beginning 20 h after the onset of food deprivation. Concentrations of triiodothyronine and thyroxine were undetectable post-THX. Plasma concentrations of thyrotropin were greater post-THX versus pre-THX (P<0 x 001). Plasma conce...
Molecular analysis using mitochondrial DNA and microsatellites to infer the formation process of Japanese native horse populations.
Biochemical genetics    February 1, 2007   Volume 45, Issue 3-4 375-395 doi: 10.1007/s10528-007-9083-0
Kakoi H, Tozaki T, Gawahara H.To assess the genetic diversity of Japanese native horse populations, we examined seven such populations using mitochondrial DNA (mtDNA) and microsatellite analyses. Four reference populations of Mongolian horses and European breeds were employed as other equids. In the mtDNA analysis, the control region (D-loop) of 411 bp was sequenced, and 12 haplotypes with 33 variable sites were identified in the Japanese native horses. The phylogenetic tree constructed by haplogrouping and using worldwide geographic references indicated that the haplotypes of the Japanese native horses were derived from s...
A lost Sorraia maternal lineage found in the Lusitano horse breed.
Journal of animal breeding and genetics = Zeitschrift fur Tierzuchtung und Zuchtungsbiologie    December 21, 2006   Volume 123, Issue 6 399-402 doi: 10.1111/j.1439-0388.2006.00612.x
Luís C, Bastos-Silveira C, Costa-Ferreira J, Cothran EG, Oom MM.A common female founder individual of the Portuguese horse breeds Sorraia and Lusitano was found while conducting research on the variation of the Lusitano mitochondrial DNA lineages in relation to studbook information. We obtained 416-bp control region sequences from 16 descendents of a female Sorraia founder (Pomba) still represented in the living population of the Lusitano, according to the most recent edition of this breed's studbook. The same haplotype was found for all analysed samples and belongs to the haplogroup described by several authors as having predominantly Iberian, South Ameri...
The horse in the ancient Near East: facts and fancies.
Veterinary heritage : bulletin of the American Veterinary History Society    December 7, 2006   Volume 29, Issue 1 15-17 
Jöchle W.No abstract available
Historical progression of racing performance in the Thoroughbred horse and man.
Equine veterinary journal    November 28, 2006   Volume 38, Issue 6 581-583 doi: 10.2746/042516406x156514
Gardner DS.No abstract available
Saving feral horse populations: does it really matter? A case study of wild horses from Doñana National Park in southern Spain.
Animal genetics    November 24, 2006   Volume 37, Issue 6 571-578 doi: 10.1111/j.1365-2052.2006.01533.x
Vega-Pla JL, Calderón J, Rodríguez-Gallardo PP, Martinez AM, Rico C.In the 1980s, a conservation programme involving a feral horse population, the Retuertas horses from the Guadalquivir marshes, was started in the Doñana National Park. The analysis of an extensive genetic survey of this population, which now numbers 100 animals, and 10 additional European and North African breeds using DNA polymorphisms from 22 microsatellites is presented. Highly significant fixation indexes were obtained for all pairwise comparisons between the Retuertas population and other breeds. A population neighbour-joining breed phenogram was built using different distance measures, ...
Strategies for construction of luteinizing hormone beta subunit analogs with carboxyl terminal extensions in non-primate, non-equid mammalian species.
Molecular and cellular endocrinology    November 7, 2006   Volume 260-262 205-211 doi: 10.1016/j.mce.2005.11.054
Ben-Menahem D, Grotjan HE.Chorionic gonadotropins (CG) are unique because they have a carboxyl terminal peptide (CTP) extension on their beta subunits that prolongs circulatory survival. CGbeta genes from the human being and horse have evolved from ancestral luteinizing hormone (LH) beta genes by different pathways that involve deletions that change the reading frames and yield a CTP. Here we further review our previous analysis, aimed at determining whether LHbeta genes in non-primate, non-equid species inherently possess DNA sequences that encode CTP-like domains. In multiple mammalian species, simple frame-shift mut...
Mitochondrial DNA sequence diversity in extant Irish horse populations and in ancient horses.
Animal genetics    September 19, 2006   Volume 37, Issue 5 498-502 doi: 10.1111/j.1365-2052.2006.01506.x
McGahern AM, Edwards CJ, Bower MA, Heffernan A, Park SD, Brophy PO, Bradley DG, MacHugh DE, Hill EW.Equine mitochondrial DNA sequence variation was investigated in three indigenous Irish horse populations (Irish Draught Horse, Kerry Bog Pony and Connemara Pony) and, for context, in 69 other horse populations. There was no evidence of Irish Draught Horse or Connemara Pony sequence clustering, although the majority of Irish Draught Horse sequences (47%) were assigned to haplogroup D. Conversely, 31% of the Kerry Bog Pony sequences were assigned to the rare haplogroup E. In addition to the extant population analyses, ancient DNA sequences were generated from three out of four Irish archaeologic...
Evidence for biogeographic patterning of mitochondrial DNA sequences in Eastern horse populations.
Animal genetics    September 19, 2006   Volume 37, Issue 5 494-497 doi: 10.1111/j.1365-2052.2006.01495.x
McGahern A, Bower MA, Edwards CJ, Brophy PO, Sulimova G, Zakharov I, Vizuete-Forster M, Levine M, Li S, MacHugh DE, Hill EW.Equine mitochondrial DNA (mtDNA) phylogeny reconstruction reveals a complex pattern of variation unlike that seen in other large domesticates. It is likely that this pattern reflects a process of multiple and repeated, although not necessarily independent, domestication events. Until now, no clear geographic affiliation of clades has been apparent. In this study, amova analyses have revealed a significant non-random distribution of the diversity among equine populations when seven newly sequenced Eurasian populations were examined in the context of previously published sequences. The associati...
Nucleotide alterations in the D3 domain of the large subunit of ribosomal DNA among 21 species of equine strongyle.
Molecular and cellular probes    September 16, 2006   Volume 21, Issue 2 111-115 doi: 10.1016/j.mcp.2006.08.008
Zhang L, Hu M, Chilton NB, Huby-Chilton F, Beveridge I, Gasser RB.The expansion segments or divergent (D) domains in the large subunit (LSU) of the ribosomal DNA have been suggested as genetic markers for taxonomic and/or phylogenetic studies of parasites. In the present study, we assessed the degree of sequence variation in the D3 domain and flanking core regions of the LSU for 21 species of equine strongyles (Strongylida: Strongylidae) and determined which positions in the secondary structure of the LSU were associated with the nucleotide alterations. No intraspecific sequence variation was detected in 17 species, for which multiple individual worms were a...
Mammalian male mutation bias: impacts of generation time and regional variation in substitution rates.
Journal of molecular evolution    September 4, 2006   Volume 63, Issue 4 537-544 doi: 10.1007/s00239-005-0308-8
Goetting-Minesky MP, Makova KD.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...
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