Estimates of ancestry and heterozygosity in an Ensatina hybrid zone. Joint maximum likelihood estimates of S and H
largely corroborate the inferences of Devitt et al.  for the Ensatina hybrid zone. The MLE ancestry index S agrees with the Bayesian Q-value from STRUCTURE (A and B). Here S is the proportion of alleles derived from E. e. klauberi. (C) The distribution of individual estimates is concentrated at S= 0 and S = 1 (putatively un-admixed individuals). The points labelled “d”, “e”, and “f” correspond to the likelihood surfaces illustrated in (D), (E), and (F). There are 20 coincident points at the top vertex (“d”), 17 of which were “confidently” assigned as F1-like. The point estimate for (e) is almost perfect for an F2-like genotype class (S = H
= 0.5), but it cannot be statistically distinguished from a klauberi backcross. Simple classification was rejected for (F) because the continuous model MLE had the lowest AIC.