The maintenance and emergence of diversity promotes open-ended evolution in a pre-cellular system

The evolution of novelty is central to understanding the emergence of life. We explored how selective contexts promote innovation, using an empirical model for pre-cellular evolution: in vitro selection of single-stranded DNA with two binding substrates, streptavidin-coated magnetic beads and yeast cells. Evolution proceeded in response to selective pressures for both binding ability and replication efficiency, and variable regimes were incorporated to investigate responses across eco-evolutionary contexts. We found that sequence diversity decreases over eight rounds of selection with beads, corresponding with an enrichment of particular sequences. During selection with cells, diversity was not only maintained but generated, producing long, complex sequences through the recombination of separate genotypes. Low selection stringency facilitated the emergence of these recombinant sequences by allowing diversity to persist, particularly during variable selection. These results demonstrate how the maintenance of diversity provides opportunities for ecological interactions which promote the emergence of innovation, transforming a pre-cellular landscape.