Studies of Mammalian Mitochondrial Genomes with Special Emphasis on the Perissodactyla

Forskningsoutput: AvhandlingDoktorsavhandling (sammanläggning)


Mammalian mitochondrial DNA (mtDNA) is a closed-circular double-helix molecule which contains two rRNA genes, 13 protein-coding genes, and 22 tRNA genes. The molecule has become a popular tool in phylogenetic analyses owing to its relatively high evolutionary rate, simple genetic structure, small size, and compact gene arrangement.

The order Perissodactyla includes the extant families Equidae, Tapiridae and Rhinocerotidae. The order and the three families are well defined, but the evolutionary relationship among the three lineages has not been settled conclusively. Some authors include the Hyracoidea in the Perissodactyla, but in the present study the narrower definition of the order is maintained.

The present analyses are based on the complete mtDNA sequence of the horse, donkey, tapir, Indian and white rhinoceroses by which the evolution of the Perissodactyla is addressed at the molecular level. Characteristics of various mammalian mtDNAs so far reported are also summarized, including a comparison of repetitive motifs occurring in the control region of many mammalian mtDNAs. Repetitive motifs of this kind characterize perissodactyl mtDNAs. Heteroplasmy with respect to the different number of repetitive motifs in different mtDNAs of the same specimen were also recorded in all perissodactyl species. The intra- and interfamilial evolutionary relationships among the perissodactyls were studied on the basis of concatenated nucleotide (nt) and amino acid (aa) sequences of all mitochondrial protein-coding genes, excluding NADH6. The analyses of the concatenated aa sequences (3,596 aa) did not resolve conclusively the relationship among the three perissodactyl families. The nt dataset of the same protein-coding genes joined Tapiridae and Rhinocerotidae to the exclusion of the Equidae. This topology was supported further by addition of the sequences of the two rRNA genes and the 22 tRNA genes. The resulting topology of the present study, based on the concatenated mitochondrial coding genes sequences (13,652 nt), is consistent with the classical view of perissodactyl relationships. Molecular dating based on a recently established reference, namely, the evolutionary divergence of artiodactyls and cetaceans set at 60 million years before the present, MYBP, dated the divergence between Perissodactyla and Artiodactyla (+ Cetacea) at ‰ 68 MYBP. The divergence between Equidae and Rhinocerotidae + Tapiridae was dated at 48 MYBP, that between the tapir and rhinoceroses at 43 MYBP, that between the Indian and white rhinoceroses at 27 MYBP, and that between the horse and the donkey at 9 MYBP.


  • Xiufeng Xu

Ämnesklassifikation (UKÄ) – OBLIGATORISK

  • Genetik


Tilldelande institution
Handledare/Biträdande handledare
  • [unknown], [unknown], handledare, Extern person
Tilldelningsdatum1996 okt 25
  • Genetics
StatusPublished - 1996
Externt publiceradJa

Relaterad forskningsoutput

Xiufeng Xu, Anettte Gullberg & Ulfur Arnason, 1996, I: Journal of Molecular Evolution. 43, 5, s. 438-446

Forskningsoutput: TidskriftsbidragArtikel i vetenskaplig tidskrift

Xiufeng Xu & Úlfur Arnason, 1994, I: Gene. 148, 2, s. 357-362

Forskningsoutput: TidskriftsbidragArtikel i vetenskaplig tidskrift

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