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Mammalian evolution: timing and implications from using the LogDeterminant transform for proteins of differing amino
D Penny1, M Hasegawa, P J Waddell
1Institute for Molecular BioSciences, Massey University, Palmerston North, New Zealand. d.penny@massey.ac.nz
Systematic Biology
|June 25, 2002
Summary
This study analyzes mammalian mitochondrial DNA (mtDNA) sequences to reconstruct evolutionary trees. Results indicate early mammal divergences before the Cretaceous–Tertiary boundary, suggesting competition with dinosaurs.
Area of Science:
- Evolutionary Biology
- Molecular Phylogenetics
- Mammalian Evolution
Background:
- Mammalian mitochondrial DNA (mtDNA) sequences are crucial for understanding evolutionary relationships.
- Amino acid composition varies significantly across mammalian species, impacting phylogenetic analyses.
Purpose of the Study:
- To reconstruct the mammalian evolutionary tree using advanced phylogenetic methods.
- To investigate the stability of the evolutionary tree and identify potential rearrangements.
- To infer divergence times of mammalian clades and their implications.
Main Methods:
- LogDet transform on amino acid sequences.
- Distance Hadamard transform for detecting alternative phylogenetic signals.
- Closest Tree selection criterion.
- Nearest-neighbor bootstrap analysis.
- Calibration using whale/cow, horse/rhinoceros, and mammal/bird divergence points.
Main Results:
- The mammalian mtDNA tree shows local stability, with some rearrangements upon removal of constant sites.
- Rodent monophyly is supported, and alternative signals suggest potential primate-rodent interchange.
- Most major mammalian divergences occurred before the Cretaceous–Tertiary (K/T) boundary.
Conclusions:
- Mammalian evolutionary history is characterized by early divergences, predating the K/T extinction event.
- These early divergences may have led to competition between nascent mammal clades and small dinosaurs.