Basal divergence of placental mammals near the phylogenetic “anomaly zone.” Expected regions of gene-tree agreement (green) and discordance (pink) under a range of possible demographic parameters at the time of the divergence of the three placental mammal superorders. The phylogenetic “anomaly zone” where concatenation will fail (red) expands as speciation intervals shorten from 5 Mya (A), to 1 Mya (B), to 0.5 Mya (C). Empirical estimates of gene-tree discord (Table 1) from retroposons (Nishihara et al. 2009) are shown with yellow tiles, whereas estimates observed in our study would occur well within the anomaly zone. Speciation intervals for this divergence are thought to be closer to 2 Mya (Murphy et al. 2004).
