Bayesian skyline plot showing Effective population size ( N
τ) through time derived from mtDNA coding region (np 577 - 16023) sequences. The thick solid line is the median estimate and the thin lines show the 95% highest posterior density limits. In this analysis N
τ, where Ne is the population of breeding females and τ is the generation length is plotted on Y axis. Time estimates obtained using a log-normal relaxed clock with the standard substitution rate of 1.26 × 10-8 sites per year  are plotted on X axis and limited to < 45 kya. Panel 'A' - The Bayesian skyline plot (m = 10) for North America (n = 75). Panel 'B' - The Bayesian skyline plot (m = 10) for Central America (n = 151, randomly selected from total 215 sequences). Panel 'C' - The Bayesian skyline plot (m = 10) for South America (n = 76). Panel 'D' - The Bayesian skyline plot (m = 10) for Beringia (n = 66).