2.5.2 Treemix
Genetic relationships were visualized for the 12 present-day blue whale
samples from the NA, three historical samples from the NA and one
historical sample from Antarctica using TREEMIX v1.13 setting a NA fin
whale as the root. The blue whale samples included here showed low
levels of introgression from fin whales. Each individual whale was
plotted with a maximum likelihood graph (with option -nos) using
genome-wide allele frequencies and a Gaussian distribution to account
for genetic drift, allowing for two migration events. Treemix was run
independently 10 times to verify that the edges were consistent across
runs. Migration edges were fitted iteratively by analyzing the residual
plots and confirming gene flow events with D-statistics.