For each Mestizo population, we computed a Pearson correlation coefficient between the Native American ancestry components (as shown in Figure 6) and the logarithm of the distance to the corresponding Native population (using the population coordinates shown in Table S1 and those reported in Wang et al.[23]). Significance of correlations was evaluated using the standard one-sided t-distribution transformation. A mean weighted correlation coefficient was obtained by averaging correlations over mestizo populations after weighting for sample size. Besides Euclidean distances, we computed effective distances using PATHMATRIX [47] and employing a 1∶10 coastal/inland cost ratio (i.e. therefore assuming that coastlines facilitated migration) (see Wang et al. (2007)[23]for details and rationale).
