The tangled nature model as an evolving quasi-species model

We show that the tangled nature model can be interpreted as a general formulation of the quasi-species model by Eigen et al in a frequency-dependent fitness landscape. We present a detailed theoretical derivation of the mutation threshold, consistent with the simulation results, that provides a valuable insight into how the microscopic dynamics of the model determines the observed macroscopic phenomena published previously. The dynamics of the tangled nature model is defined on the microevolutionary time scale via reproduction, with heredity, variation and natural selection. Each organism reproduces at a rate that is linked to the individuals' genetic sequence and depends on the composition of the population in genotype space. Thus the microevolutionary dynamics of the fitness landscape is regulated by, and regulates, the evolution of the species by means of the mutual interactions. At low mutation rate, the macroevolutionary pattern mimics the fossil data: periods of stasis, where the population is concentrated in a network of coexisting species, are interrupted by bursts of activity. As the mutation rate increases, the duration and the frequency of bursts increase. Eventually, when the mutation rate reaches a certain threshold, the population is spread evenly throughout the genotype space showing that natural selection only leads to multiple distinct species if adaptation is allowed time to cause fixation.