Tracking of wisent-bison-yak mitochondrial evolution

Area of Science:

• * Molecular Biology
• * Evolutionary Genetics
• * Zoology

Background:

• * Mitochondrial DNA (mtDNA) is crucial for understanding species origins and phylogenetics.
• * Identifying similarities between wild and domestic species aids evolutionary studies.
• * The Bovini tribe, including cattle, bison, and yak, presents complex evolutionary relationships.

Purpose of the Study:

• * To investigate the maternal evolutionary relationships within the Bovini tribe using mitochondrial DNA.
• * To determine the divergence times and phylogenetic placement of wisent and American bison.
• * To analyze the evolutionary impact of potential mitochondrial DNA transfer events between species.

Main Methods:

• * Analysis of nucleotide sequences from the mitochondrial DNA (mtDNA) coding regions of various bovine haplotypes, wisent, auroch, bison, and yak.
• * Exclusion of non-coding D-loop regions, utilizing a final dataset of 15,419 base pairs.
• * Construction of phylogenetic trees based on whole mitochondrial genomes and coding sequences alignment.

Main Results:

• * Phylogenetic trees largely align with previous Bovini tribe studies.
• * American bison exhibit stronger maternal lineage connections to yak than to wisent.
• * Wisent divergence is estimated to have occurred early, between 2 and 1.6 million years ago, consistent with Late Pleistocene speciation.
• * Evidence supports a yak/bison mitochondrial DNA transfer model occurring around 700,000 years ago, with distinct mutations accumulating before and after the event.
• * Wisent and bison maintained mtDNA variability despite population bottlenecks.

Conclusions:

• * The study refines the understanding of evolutionary timelines and maternal lineages within the Bovini tribe.
• * It provides strong evidence for an ancient mitochondrial DNA transfer event between yak and bison.
• * Wisent and bison demonstrate resilience in mtDNA variability, even after population size reductions.