(a) Attine synteny loss per MY divergence compared with other lineages with sequenced genomes. Box-percentile plots summarize the distribution of pairwise comparisons (number given after lineage name) within each clade, with means and percentiles marked. The overall difference between lineages was highly significant (n=6, Kruskal–Wallis H=101.247, P<0.0001). Shared letters indicate groups that did not differ significantly (Steel–Dwass test, P>0.05). (b) Synteny loss mapped onto the phylogeny of all ants with sequenced genomes, comparing each node with the earliest common ancestor (vertical axis) and with polygons shaded according to rate of loss per branch. (c) Numbers of expanded (red arrows) or contracted (blue arrows) gene families inferred from observed gene family sizes at terminal branches. (d) Functional erosion of the arginine synthesis pathway, with the argininosuccinate lyase gene (green) probably being lost in the attine ancestor and the argininosuccinate synthase gene (blue) remaining recognizable as pseudogenized residues in some genomes. Approximate lengths of pseudogenes (light blue bars) are shown relative to the S. invicta coding sequence of 1,239 bp. Red symbols in the branches and bars mark the origins and approximate locations of indels or in-frame stop codons: dots: lineage specific mutations; diamonds: ancestral mutations for T. septentrionalis, Acromyrmex and Atta; triangles: ancestral mutations for Acromyrmex and Atta; squares: ancestral mutations for Atta.