Fig. 2: Demographic history of Z. bungeanum and Z. armatum.

a Historical effective population size (Ne) for Z. bungeanum (left) and Z. armatum (right) clades from ~1.8 million years ago (mya) to present. The Ne of each clade was rescaled using the generation time g = 4 years and mutation rate per year μ = 2.6 × 10−9; ref. 20. The stairway plot shows that Z. bungeanum clades have undergone an apparent steep decline in Ne since the LGM, whereas the LGM did not result in population declines in Z. armatum clades. Light blue represents the last glacial period (70−11.5 thousand years ago, kya), and the dark blue shadow represents the LGM (26−18 kya). Data are median estimates from 200 bootstrap replicates (black line), 95% confidence intervals (light shading), and 75% confidence intervals (dark shading). b Schematic model of a demographic scenario based on population splitting and changes in Ne revealed by fastSIMCOAL2