On the Origin of Genetic Diversity

Abstract

The organic diversity found in nature today is ultimately a consequence of a continuous cycle of building up genetic diversity, which is subsequently channeled by natural selection, chance events, and by geographic or other modes of speciation. Whereas modern evolutionary theory provides detailed explanations of the mechanisms channeling genetic diversity, little is known on the evolutionary forces responsible for the presence and the properties of processes that create genetic diversity. Conventionally, genetic diversity is viewed as the outcome of mutation mechanisms that are not themselves optimized by natural selection. In contrast, a great number of hypotheses are available on the adaptive significance of meiosis, sex and general genetic recombination in eukaryotes, which are mechanisms for the “management” of genetic diversity, but not for its production. In this contribution, we argue that bacteria have evolved elaborate mechanisms for the production of genetic diversity. These mechanisms could themselves be subject to adaptation by natural selection. A selection mechanism termed second-order selection is discussed which could account for the abundance of genes that cause random DNA sequence variation in bacteria.