Fig. 2
The demographic and split history of the C. hamatus populations. A Demographic history (Effective Population Size, the left y-axis) of the 4 populations constructed with SMC++ modelling. Generation time (g) is set at 7 years and neutral mutation rate per generation (μ) at 2.85 × 10−8. The blue and gray gradient represents the ice volume change (the right-side y-axis) over time in Antarctica, adopted from [20, 22] as a proxy of the seawater δ18O. The white background shows periods of lowest ice volume, corresponding to the peak interglacial warming periods. The x-axis represents years to present time. B–E Enlarged views of parts (2 × 104–105 years ago) of Fig. 3A to show the estimated split times between the populations. The split time is indicated by a vertical dotted line, with the corresponding number in years to the right. B–D show the split between RS1 (red) and ZD1 (green), RS1 (red) and RS2 (blue), RS2 (blue) and ZD1 (green) respectively, and E showing a more recent separation between ZD1 (green) and ZD2 (purple). F Maximum likelihood tree inferred by TreeMix with two migration events. Arrows are colored according to their migration weight and horizontal branch lengths are proportional to the amount of genetic drift. G Genetic structure of the individuals of the 4 C. hamatus populations inferred from ADMIXTURE by varying the ancestry components (K) from 1 to 7