How does the mode of reproduction affect transposable element dynamics? Previous theoretical work suggested either a accumulation or decrease of TE copies in the absence of sexual repdrocution. In non-recombining portions of genomes in sexual organisms, typically an accumulation is found. But empirical estimates in natural populations of completely asexual organisms compared to sexuals could not detect any TE load difference. This is probably due to many confounding effects like hybridization or polyploidy or differences in population sizes masking TE dynamics. How to find out?
Experimental evolution can help. McDonald et al. have produced replicate lines of yeast with a common ancestral genetic background both allowing and disabling sexual reproduction. These lines were evolving for almost one thousand generations and were sequenced every 90 generations. We used this dataset to estimate TE dynamics in the yeast. We found that TE numbers decline in asexual yeast almost by 20% after 1000 generations, whereas sexuals maintain a stable 'equilibrium' TE load. We further simulated the experiment to generate insights into the mechanism behind and developed a theory that could explain the observed data.
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