The role of weak selection and high mutation rates in nearly neutral evolution

Abstract

International audienceNeutral dynamics occur in evolution if all types are ‘effectively equal' in their reproductive success, where the definition of ‘effectively equal' depends on the population size and the details of mutations. Empirically observed neutral genetic evolution in extremely large clonal populations can only be explained under current models if selection is completely absent. Such models typically consider the case where population dynamics occurs on a different timescale to evolution. However, this assumption is invalid when mutations are not rare in a whole population. We show that this has important consequences for the occurrence of neutral evolution in clonal populations. In highly connected type spaces, neutral dynamics can occur for all population sizes despite significant selective differences, via the forming of effectively neutral networks connecting rare neutral types. Biological implications include an explanation for the high diversity of rare types that survive in large clonal populations, and a theoretical justification for the use of neutral null models

Genetic differentiation ofTrifolium repensmicrosymbionts deriving from Zn-Pb waste-heap and control area in Poland

“…This evolutionary force, particularly effective within small populations, refers to random changes in the gene variant frequencies that can lead to genetic divergence of populations entirely by chance. According to the Kimura's neutral theory of molecular evolution , neutral mutations can be accumulated over time due to genetic drift and these mutations can shape the genetic structure of populations, but without effect on the health and survival of an organism in a given environment . This theory assumes that genetic polymorphism within population resulting from the presence of neutral mutations is shaped by the equilibrium between genetic drift and mutations.…”