Figure 4: Historical effective population size for silver birch beginning from 80 million years ago to present.

Stairway plot showing that the B. pendula population has undergone bottlenecks during four known periods of major climate upheaval: the K–Pg (green) the Eocene-Oligocene (E–Og; blue), the mid-Miocene (M; red), and the Pleistocene (Ple; purple). Data are median estimate from 200 bootstrap replicates (black line) and 95% confidence intervals (shading). Tick marks along the x axis show estimates for the Matuyama–Brunhes (0.77 Mya), Calabrian (1.8 Mya), and Gelasian (2.58 Mya) borders; the mid-Miocene disruption (14.5–14.8 Mya), and the E–Og (34 Mya) and K–Pg (66 Mya) events.