Genetic saturation is the reduced appearance, which occurs over time, of sequence divergence rate that results from reverse mutations, homoplasies and other multiple changes occurring at single sites along two lineages.
Genetic saturation is a cause of reticulation in genetic trees, where diverging genetic branches might fuse back into one another before splitting. Two other causes are sequence errors and recombination.
Genetic saturation occurs most rapidly on rapidly evolving sequences, such as the hypervariable region of mitochondrial DNA, or in Short tandem repeat such as on the Y-chromosome.