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Published on: August 14, 2018
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INFERRING PHYLOGENIES FROM mtDNA VARIATION: MITOCHONDRIAL-GENE TREES VERSUS NUCLEAR-GENE TREES
1Department of Biological Sciences, Wayne State University, Detroit, Michigan, 48202.
Summary
Mitochondrial DNA (mtDNA) gene trees are more reliable for inferring species trees in birds than nuclear genes due to faster coalescence. Recent bird mtDNA studies show lineage sorting rarely confounds species tree estimation.
Area of Science:
- Evolutionary biology
- Phylogenetics
- Population genetics
Background:
- Gene trees may not match species trees due to lineage sorting of ancestral polymorphisms.
- Mitochondrial DNA (mtDNA) evolves rapidly, aiding phylogeny estimation in recent taxa, but its single linkage group limits independent estimates.
- Nuclear genes from distinct chromosomes offer independent estimates but may have lower congruence with species trees.
Purpose of the Study:
- To evaluate the utility of mtDNA versus nuclear genes for inferring species trees, particularly in recently diverged taxa.
- To assess the impact of coalescence rates and effective population size on gene tree-species tree congruence.
- To determine the reliability of mtDNA haplotype trees for reconstructing avian phylogenies.
Main Methods:
- Comparative analysis of gene tree congruence with species trees based on neutral theory and effective population size.
- Utilizing neutral theory to model coalescence probabilities for mitochondrial and nuclear genes.
- Surveying mtDNA haplotype diversity in 34 bird species to assess coalescence times relative to species tree internodes.
Main Results:
- Mitochondrial DNA, with its smaller effective population size, exhibits a higher probability of accurate lineage sorting for short internodes compared to nuclear genes.
- A single mtDNA haplotype tree is more congruent with the species tree than a single nuclear gene tree; 16 nuclear gene trees may be needed for equivalent confidence.
- Bird mtDNA studies indicate recent coalescence, suggesting mtDNA lineage sorting is unlikely to confound species tree inference, though hybridization requires careful consideration.
Conclusions:
- Mitochondrial DNA is a powerful tool for inferring species trees, especially for recently diverged taxa, due to its rapid coalescence.
- While hybridization can lead to incongruence, it is typically detectable and can be integrated into evolutionary narratives.
- The rapid coalescence of mtDNA makes it a more reliable marker than nuclear genes for resolving short internodes in species phylogenies.
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