Population structure analysis
SNPs that were covered in all the individuals were used to estimate the
genetic structure of North American monarchs. Principal component
analysis (PCA) of the SNPs was performed using SNPRelate
(Zheng et al. , 2012) in the
R/Bioconductor package. Cross validation error rates were checked using
ADMIXTURE (Alexander, Novembre & Lange,
2009) for âKâ values ranging from 1 to 5 to determine the total number
of populations in the dataset.