Table 1 Summary of the models implemented in this work
ModelDescriptionParameters
Equal species meansAll species have the same mean gene expression levelμ: global mean gene expression level
Unequal species meansAll species have their own independent mean gene expression levelμi: mean gene expression level per species
Brownian motionRandom drift of the species’ mean gene expression level along the phylogenyσ2: rate of drift
Brownian motion with shiftRandom drift with one branch having a different rate (directional selection)σ2B: rate of drift background branch
σ2F: rate of drift foreground branch
Ornstein–UhlenbeckStabilizing selection of the species mean gene expression level evolving along the phylogenyσ2: rate of drift
α: strength of selection
θ: optimal gene expression level
Ornstein–Uhlenbeck with shiftDirectional selection due to a shift in optimal gene expression levelσ2B: rate of drift background branch
σ2F: rate of drift foreground branch.
θB: optimal gene expression level background branch
θF: optimal gene expression level foreground branch
α: strength of selection