DGM Is Dead; Long Live DGM-Star! A Quantization-Theoretic Approach to Gamma Rate Discretization

A quantization-theoretic Gamma rate discretization for phylogenetic inference reduces bias in estimated branch lengths, achieving up to a 20-fold reduction on simulated phylogenies.

• Why it matters: Standard discrete Gamma model (DGM) discretization can substantially overestimate average branch lengths when true rates come from a continuous Gamma distribution, leaving a practical accuracy gap.
• What they did: The authors derive a drop-in replacement discretization using quantization-theoretic tools on a simplified star-phylogeny abstraction, where the new method is unbiased by construction.
• The result: The approach works especially well on large trees with short branches and can mitigate Ferretti et al.’s finding that increasing rate categories may worsen DGM bias.

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