Fig 1. Bar plots of population clustering estimated through the Bayesian clustering algorithm Structure with K = 8 for specimens of Drymarchon couperi (Eastern Indigo Snake).

The y-axis is the proportion of individual ancestry for each cluster; in the x-axis, number represents county where sample was collected. County names for each number are shown in S5 Table. Some counties (e.g., 12–26) are overlapping on the x-axis due to small sample size per cluster.