Conclusion
There is a global metabolic network available for animals (Borenstein et al. 2008), and we are still in the early stages of uncovering how this network is structured across the animal tree of life (Fig. 1, Fig. 4, Table 1) and how it is mechanistically linked to fitness variation of consumers (Table 2, Fig. 5). Empirical studies have documented substantial variation in the fatty acids of organisms, structured both within and among ecosystems and among prey communities, which creates ample opportunities for the evolution of consumer behavior and metabolism. Indeed, there is growing evidence for evolutionary diversification in the primary nodes and controls of the fatty acid metabolic network (Fig. 4). Studying such metabolic diversity across multiple scales (Fig. 4, 5), will allow us to understand more broadly how consumers evolve traits related to both resource acquisition and metabolism, and how they invade new environments and diversify.