Competitive Exclusion among Self-Replicating Molecules Curtails the Tendency of Chemistry to Diversify

The transition of chemistry into biology is poorly understood. One of the key questions in this transition is how the inherently divergent nature of chemical reactions can be curtailed, allowing product mixtures to become enriched in only a limited subset of all possible reaction products. Another seemingly unrelated question is whether Darwinian principles from biology extend to chemistry. Addressing both questions simultaneously, we now show that the evolutionary principle of competitive exclusion, which states that a single niche can only be stably occupied by one species, also applies to self-replicating chemical systems, and that this principle diminishes the tendency of chemistry to diversify. Specifically, we report two systems in which three different self-replicator quasi-species emerge in a largely stochastic fashion from a mixture of two building blocks (resources). To enable their evolution, these replicator mixtures were subjected to an out-of-equilibrium replication-destruction regime, implemented by serial transfer. Out of the many different products initially produced, competitive exclusion leads to the selection of only a single quasi-species when all replicators rely to the same extent on both resources. When, on the other hand, one of the quasi-species preferentially uses one resource and another quasi-species specializes in the other (resource partitioning), these replicator quasi-species effectively occupy different niches and were found to coexist in an evolutionary stable steady state. The ability to escape from competitive exclusion through resource partitioning is important for future efforts on addressing a major evolutionary challenge on the path to life’s emergence: Eigen’s paradox, which requires evolutionary stable communities of co-existing replicators with specific community dynamics.