engleski

Fast molecular evolution under neutral-adaptive conversion: a possible mechanism for the evolution of novel genes

A fundamental problem in evolutionary biology is to connect microevolution based on population genetics with macroevolution, which is characterized by the appearance of novel genes leading to evolutionary innovations. Evolution has two visible manifestations: genetic variation (polymorphism) and evolutionary change (rate of molecular evolution). Maintenance of genetic variation has direct implications for the rate of molecular evolution (Brčić-Kostić, 2005, Genet. Res. 86, 53-63.). Fast molecular evolution is the most plausible mechanism for the formation of a novel gene from an ancestor gene. Finding a model for the maintenance of genetic variation which allows fast molecular evolution is therefore crucial to our understanding of the evolution of novel genes, and the formation of evolutionary innovations at the molecular level. Using simulations and analytical models, we examined the rate of molecular evolution at a single locus in three scenarios. We found that for realistic parameter sets, molecular evolution is faster when previously neutral alleles become adaptive (neutral-adaptive conversion), than when evolution results from either novel adaptive mutations or mutation-selection balance. We show that the adaptive rate of gene substitution under neutral-adaptive conversion is equal to the product of the rate of neutral-adaptive conversion per allele per generation, the average number of alleles and the average probability for the fixation of an allele from previously neutral polymorphism. We propose that neutral-adaptive conversion can be a suitable mechanism for fast evolution of particular genes underlying major evolutionary innovations.

neutral-adaptive conversion; standing genetic variation; molecular evolution; evolutionary innovation

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