The population genetics of ploidy change in unicellular fungi

Changes in ploidy are a significant type of genetic variation, describing the number of chromosome sets per cell. Ploidy evolves in natural populations, clinical populations, and lab experiments, particularly in unicellular fungi. Predicting how ploidy will evolve has proven difficult, despite a long history of theoretical work on this topic, as it is often unclear why one ploidy state outperforms another. Here, we review what is known about contemporary ploidy evolution in diverse fungal species through the lens of population genetics. As with typical genetic variants, ploidy evolution depends on the rate that new ploidy states arise by mutation, natural selection on alternative ploidy states, and random genetic drift. However, ploidy variation also has unique impacts on evolution, with the potential to alter chromosomal stability, the rate and patterns of point mutation, and the nature of selection on all loci in the genome. We discuss how ploidy evolution depends on these general and unique factors and highlight areas where additional experimental evidence is required to comprehensively explain the ploidy transitions observed in the field, the clinic, and the lab.

Automated summary

Changes in ploidy, describing the number of chromosome sets per cell, are a significant type of genetic variation that evolves in various populations and experiments. Ploidy evolution is influenced by mutation rates, natural selection, and genetic drift, with unique impacts on evolution like altering chromosomal stability and mutation patterns. Additional experimental evidence is needed to comprehensively explain observed ploidy transitions.