Fig. 1: Phylogeny and population structure of the Guinness yeast and other industrial S. cerevisiae strains.

a Guinness and other Irish brewing yeast within the maximum-likelihood phylogenetic tree of S. cerevisiae. Guinness and other Irish brewing yeast were sequenced using an Illumina MiSeq platform and combined with 154 previously sequenced S. cerevisiae⁴. Branch length reflects the number of substitutions per site, with colour denoting the yeast lineage. A maximum-likelihood (ML) phylogenetic tree was reconstructed in RAxML v8.2.4¹⁵, performing 100 iterations to search for the best tree, using a discrete GTRGAMMA model of rate heterogeneity. Bootstrap branch support was assessed by performing 1000 pseudoreplicates. Trees were visualised using ggtree (v 3.6.2)¹⁶. Yeasts that are marked in highlighted orange are described as being Mosaic⁴. Yeast marked with three asterisk are used to brew beers in the Hefeweizen style. b Principal component analysis of 434,890 SNPs sites from the assessed 176 S. cerevisiae strains. Population differences indicated by colour; NS not specified. c Population structure of the 434,890 SNPs sites of the S. cerevisiae strains used in this study. IDS1 was used as a representative Guinness yeast sample for all Guinness yeast due to the high degree of sequence similarity analysis consequently 161 genomes admixture were assessed. Resolved population fractions are represented by the vertical axis; colours denote estimated ancestral membership. Varying the number of ancestral populations (K) between 1 and 10 using the simple prior implemented in fastSTRUCTURE¹⁷, K = 8 found to be optimal.