Asexual reproduction, polyploidy and optimal mutation rates

Abstract

Apomictic plant and animal species are very often polyploids. Such species are usually derived from diploid sexual ancestors. It is argued that mutation rates in sexual species are minimal. On the other hand in asexuals selection tends to optimize the mutation rate because mutator genes remain linked to the favourable mutations they create. Polyploidy is a mutation which increases the mutation rate per individual. Therefore polyploidy evolves in asexual groups because it optimizes the mutation rate per individual. The argument predicts that asexual reproduction with polyploidy should be correlated with variable environments and simple body structure of organisms. More surprisingly it indicates that the major long-term disadvantage of asexual reproduction comes with environmental constancy and not variability. Optimal mutation rates may also represent a major advantage for polyploidy in non-apomictic organisms. The consequences and evidence for this idea are discussed.