Shown are median values and, in parentheses, lower and upper quartiles. P-values are calculated using the Kolmogorov-Smirnov test.

^aP-values were calculated using the Kolmogorov-Smirnov test.

^bThe elevated d_N/d_S for Trichosurus–Monodelphis orthologs is likely to be due to EST sequencing errors appearing as nonsynonymous changes. This would also explain the lower significance (higher P-value) for the decrease in subtelomeric d_N/d_S for these two species.