Gene number expansion and contraction in vertebrate genomes with respect to invertebrate genomes

The family-size correlation between the vertebrate and invertebrate genomes. Scatter plots, on the log-scale axes, show the average vertebrate family size (n_v) against the average invertebrate family size (n_i) for each V.MCL gene family. The black solid line represents n_v = n_i, while the one-dashed and two-dashed lines represent the fitted lines from the simple linear regression model and the robust linear regression model, respectively (n_v = β₀ + β₁ n_i). The slopes (i.e., β₁ estimates) for the one-dashed and two-dashed fitted lines are 1.15 (R² = 0.63) and 0.92, with the bootstrapped 95% confidence intervals of β₁ estimates being (0.72, 1.54) and (0.78, 1.09), respectively. The bootstrapped P-values are 0.73 and 0.21 for the null hypothesis of β₁ = 1 from the simple regression model and the robust linear regression model, respectively, so that the slopes are not significantly different from 1.