Multilevel Selection in Models of Prebiotic Evolution II: A Direct Comparison of Compartmentalization and Spatial Self-Organization

Abstract

Multilevel selection has been indicated as an essential factor for the evolution of complexity in interacting RNA-like replicator systems. There are two types of multilevel selection mechanisms: implicit and explicit. For implicit multilevel selection, spatial self-organization of replicator populations has been suggested, which leads to higher level selection among emergent mesoscopic spatial patterns (traveling waves). For explicit multilevel selection, compartmentalization of replicators by vesicles has been suggested, which leads to higher level evolutionary dynamics among explicitly imposed mesoscopic entities (protocells). Historically, these mechanisms have been given separate consideration for the interests on its own. Here, we make a direct comparison between spatial self-organization and compartmentalization in simulated RNA-like replicator systems. Firstly, we show that both mechanisms achieve the macroscopic stability of a replicator system through the evolutionary dynamics on mesoscopic entities that counteract that of microscopic entities. Secondly, we show that a striking difference exists between the two mechanisms regarding their possible influence on the long-term evolutionary dynamics, which happens under an emergent trade-off situation arising from the multilevel selection. The difference is explained in terms of the difference in the stability between self-organized mesoscopic entities and externally imposed mesoscopic entities. Thirdly, we show that a sharp transition happens in the long-term evolutionary dynamics of the compartmentalized system as a function of replicator mutation rate. Fourthly, the results imply that spatial self-organization can allow the evolution of stable folding in parasitic replicators without any specific functionality in the folding itself. Finally, the results are discussed in relation to the experimental synthesis of chemical Darwinian systems and to the multilevel selection theory of evolutionary biology in general. To conclude, novel evolutionary directions can emerge through interactions between the evolutionary dynamics on multiple levels of organization. Different multilevel selection mechanisms can produce a difference in the long-term evolutionary trend of identical microscopic entities.

Simulating the origins of life: The dual role of RNA replicases as an obstacle to evolution

“…In all experiments, the affinity of replicases towards replicases was equal to a R = 0.7 and the replicases were catalytically active regardless of their folded state. The value of a R differs from the value that was used in the experiments by Takeuchi and Hogeweg [33], where it was set to 0.6. We also examined the value a R = 0.6; however, closer investigation showed that while a slightly higher value of this parameter equal to 0.7 does not change the characteristics of the system, it does give better results in terms of a more stable coexistence between parasites and replicases, meaning that we could more easily observe the emerging behaviors in the system.…”

Co-operation between Polymerases and Nucleotide Synthetases in the RNA World

“…The origin of cells is a key early step in the evolution of life, but it is not yet clear just how early this step is. It is quite difficult to compare models of spatial clustering and protocells because they tend to be formulated in different ways, although see [43] for a good attempt at doing this.…”

The dynamics of the RNA world: insights and challenges

“…This process protects the population from extinction and results in evolutionary dynamics yielding a stable quasispecies at the level of compartments 162 . The SCM is inherently stable against parasites: it has the ability to select against inferior and select for superior mutants [163][164][165][166] . The cells of the SCM are individuals subject to selection and are thus evolutionary units.…”