The Tangled Nature model as an evolving quasi-species model

摘要

We show that the Tangled Nature model can be interpreted as a generalformulation of the quasi-species model by Eigen et al. in a frequency dependentfitness landscape. We present a detailed theoretical derivation of the mutationthreshold, consistent with the simulation results, that provides a valuableinsight into how the microscopic dynamics of the model determine the observedmacroscopic phenomena published previously. The dynamics of the Tangled Naturemodel is defined on the microevolutionary time scale via reproduction, withheredity, variation, and natural selection. Each organism reproduces with arate that is linked to the individuals' genetic sequence and depends on thecomposition of the population in genotype space. Thus the microevolutionarydynamics of the fitness landscape is regulated by, and regulates, the evolutionof the species by means of the mutual interactions. At low mutation rate, themacro evolutionary pattern mimics the fossil data: periods of stasis, where thepopulation is concentrated in a network of coexisting species, is interruptedby bursts of activity. As the mutation rate increases, the duration and thefrequency of bursts increases. Eventually, when the mutation rate reaches acertain threshold, the population is spread evenly throughout the genotypespace showing that natural selection only leads to multiple distinct species ifadaptation is allowed time to cause fixation.