In all panels, the left schematic indicates supply rates, the central plot shows an example of competitive population dynamics, and the right diagram depicts the final strategies and their internal building-block per-cell fluxes. (A) If the building blocks are supplied with equal stoichiometry , metabolic strategies that carry out conversions are wasteful and a single pure-importer cell type prevails. (B) If two building blocks are supplied with equal stoichiometry, e.g. and , three cell types can coexist: two ‘symmetric’ types using supplied blocks as a precursor for block , which accumulates externally due to passive leakage and release upon cell death, and, if is large enough, a third pure-importer type. (C) For large enough imbalance in the supply of building blocks and , e.g. , three distinct cell types can coexist: a pure-converter type imports block and converts blocks and ; if is large enough, a mixed type emerges, importing blocks and , and converting to ; and, if is large enough, a pure-importer type. (D) If only one building block is supplied, e.g. , two strategies coexists: a pure-converter type releases blocks and , which can lead to the emergence of a pure-importer type. The external building-block concentrations fluctuate, albeit only slightly later in the simulations, due to the invasion by and extinction of metabolic variants.