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Fig. 1 | Biology Direct

Fig. 1

From: Tradeoff between robustness and elaboration in carotenoid networks produces cycles of avian color diversification

Fig. 1

Metabolic pathway elongation and robustness are structurally linked in avian carotenoid-producing networks. a Metabolic elongation (reactions shown as arrows) necessarily starts with dietary carotenoids (green circles) and over evolutionary time can invade the biochemical domain of another dietary carotenoid (i.e., nodes reachable from another dietary compound; dashed line), resulting in dietary robustness of a shared compound (red circle). b Metabolic distance between species increases with their evolutionary distance (patristic distance). c Relationship between metabolic and evolutionary divergence (slopes from Fig. 1b: standardized regression coefficient, bST, in standard deviations (SD)) in carotenoid-producing pathways over different time scales calculated separately for subnetworks containing only dietary, intermediate, or plumage-expressed compounds. Across time periods, divergence in dietary carotenoids increases with evolutionary distance (upper), whereas divergence in intermediate (metabolized, but not expressed) compounds (middle) lessened with evolutionary distance as a result of greater occupancy of shared metabolic space among distinct dietary (external) starting points (Fig. 1a). Concordance between metabolic and evolutionary distances was particularly strong in most recently diverged species (<20 my) and was largely produced by differential expression of compounds (lower panel) and their metabolic evolution (middle panel) and not by switching between dietary starting points in metabolic pathways (upper panel). *– indicates slopes different from zero at P = 0.05, ns marks two slopes that did not differ from zero, all other slopes differ from zero at P < 0.01

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