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Rooting a phylogenetic tree with nonreversible substitution models
1Mathematics Department, University of California, 970 Evans Hall, Berkeley, CA 94720, USA. vonbing@math.berkeley.edu
BMC Evolutionary Biology
|January 5, 2005
Summary
The nonstationary process significantly outperforms the stationary process in correctly rooting phylogenetic trees without an outgroup. This method offers a simpler and more accurate approach for root inference in evolutionary biology.
Area of Science:
- Evolutionary biology
- Phylogenetics
- Molecular evolution
Background:
- Phylogenetic tree rooting is crucial for understanding evolutionary relationships.
- Traditional methods often require an outgroup, which may not always be available.
- Two rooting methods, stationary and nonstationary substitution processes, were compared.
Purpose of the Study:
- To evaluate the efficacy of stationary versus nonstationary substitution processes for phylogenetic tree rooting.
- To determine which method provides more accurate root placement, especially when an outgroup is absent.
Main Methods:
- Maximum likelihood estimation was used to determine branch lengths and substitution parameters for rooted trees.
- Rooted trees were compared based on their likelihood values.
- Variation in substitution rates across sites was addressed by classifying sites into distinct rate categories.
Main Results:
- The nonstationary process demonstrated significantly higher accuracy in root estimation compared to the stationary process across three test datasets.
- The nonstationary process provided a substantially better fit to the data.
- Both methods yielded biologically plausible root placements for primate mitochondrial DNA sequences.
Conclusions:
- The nonstationary substitution process is a more effective and user-friendly method for inferring phylogenetic tree roots.
- This approach is particularly valuable in scenarios where an outgroup is not available for phylogenetic analysis.