Heterotachy, an important process of protein evolution.

@article{Lopez2002HeterotachyAI,
  title={Heterotachy, an important process of protein evolution.},
  author={Philippe Lopez and Didier Casane and Herv{\'e} Philippe},
  journal={Molecular biology and evolution},
  year={2002},
  volume={19 1},
  pages={1-7}
}
Because of functional constraints, substitution rates vary among the positions of a protein but are usually assumed to be constant at a given site during evolution. The distribution of the rates across the sequence positions generally fits a Gamma distribution. Models of sequence evolution were accordingly designed and led to improved phylogenetic reconstruction. However, it has been convincingly demonstrated that the evolutionary rate of a given position is not always constant throughout time… CONTINUE READING