Fig. 3.

Evidence for assortative mating and low rates of cross-cluster hybridization in Aguazarca, but not Totonicapa. (A) Observed differences between maternal and offspring indices in Aguazarca are tightly clustered around zero (black points), indicating that females mate with males of similar ancestry. Cross-cluster matings are predicted to occur at high frequency in simulations of random mating (blue points in Lower Left and Upper Right corners) but are absent from the population. (B) In contrast, in Totonicapa, observed mating events more closely match random mating. (C and D) Examples of the raw data used to generate ancestry estimates. The plots show ancestry across chromosome 1 for representative mother-offspring pairs from each population (purple triangles in the upper panels). The solid red regions are homozygous for X. birchmanni, whereas the solid blue regions are homozygous for X. malinche. Unshaded regions are heterozygous. The height of each region indicates the posterior probability of the ancestry call. Mothers and offspring sampled from Aguazarca have strongly similar ancestry across the chromosome (C), whereas in some cases mothers and offspring from Totonicapa show strikingly different ancestry patterns (D).