Synthetic Eco-Evolutionary Dynamics in Simple Molecular Environment

Abstract

The understanding of eco-evolutionary dynamics, and in particular the mechanism of coexistence of species, is still fragmentary and in need of test bench model systems. To this aim we developed a variant of SELEX in-vitro selection to study the evolution of a population of [~] 1015 single-strand DNA oligonucleotide individuals. We begin with a seed of random sequences which we select via affinity capture from [~] 1012 DNA oligomers of fixed sequence ( resources) over which they compete. At each cycle ( generation), the ecosystem is replenished via PCR amplification of survivors. Massive parallel sequencing indicates that across generations the variety of sequences ( species) drastically decreases, while some of them become populous and dominate the ecosystem. The simplicity of our approach, in which survival is granted by hybridization, enables a quantitative investigation of fitness through a statistical analysis of binding energies. We find that the strength of individual-resource binding dominates the selection in the first generations, while inter and intra-individual interactions become important in later stages, in parallel with the emergence of prototypical forms of mutualism and parasitism.