Fig. 2.

Relationships between number of species and total branch lengths of gene trees. a mtDNA datasets with $\mu$_m/$\mu$_n < 20, R² = 0.934, P < 2.2 × 10^–16; b mtDNA datasets with $\mu$_m/$\mu$_n > 20, R² = 0.778, P < 7.8 × 10^–8; c nuDNA datasets with $\mu$_m/$\mu$_n < 20, R² = 0.705, P < 2.2 × 10^–16; d nuDNA datasets with $\mu$_m/$\mu$_n > 20, R² = 0.652, P < 5.8 × 10^–6