Fig. 9

Sequential gains of new dietary paths “rescue” ongoing elaboration. Avian phylogenetic tree (Additional file 4: Figure S1) scaled to reflect the rate of carotenoid elaboration (reactions per million years). Most branches had negligible rates and are not shown. Branches colored according to the number of new dietary pathways gained (red), lost (blue), or retained the same (black) at each node. For species with accelerated metabolic evolution (longer branch length), the length of bar at tips indicates the longest path from dietary to plumage carotenoids (dietary elaboration, in number of reactions). These elaboration bars are partitioned by the exact ratios of biochemical scopes of distinct dietary compounds (shown by compound colors, legend) that contributed to dietary elaboration. Greater dietary elaboration was associated with greater number of similarly contributing dietary scopes, supporting the coevolution of elaboration and robustness scenario in Fig. 8, right). Thraupidae and Muscicapidae clades offset to shown details