An evolutionary epigenetic clock in plants.

Area of Science:

• Evolutionary biology
• Genomics
• Epigenetics

Background:

• Molecular clocks based on DNA sequences are essential for macroevolutionary dating but are too slow for recent evolutionary history.
• Classical DNA clocks operate on timescales of 10⁵ to 10⁸ years, limiting their utility for recent diversification events.

Purpose of the Study:

• To introduce and validate a novel high-resolution molecular clock based on DNA methylation changes.
• To demonstrate the utility of this "epimutation clock" for reconstructing recent plant phylogenies.

Main Methods:

• Investigated stochastic DNA methylation changes at specific cytosines in plant genomes.
• Developed and applied the "epimutation clock" for phylogenetic dating on timescales of years to centuries.
• Experimentally validated the clock's accuracy using *Arabidopsis thaliana* and *Zostera marina*.

Main Results:

• DNA methylation changes exhibit clocklike behavior, operating orders of magnitude faster than DNA-based clocks.
• The epimutation clock successfully recapitulated known intraspecies phylogenetic trees and divergence times.
• Validated findings in both a self-fertilizing plant (*Arabidopsis thaliana*) and a clonal plant (*Zostera marina*).

Conclusions:

• The epimutation clock provides a powerful new tool for high-resolution temporal studies in plant evolution.
• This discovery opens avenues for exploring plant biodiversity and evolutionary dynamics on recent timescales.
• Epigenetic changes offer a faster, more precise method for phylogenetic analysis in plants.