The case of the missing ancient fungal polyploids

Polyploidy—the increase in the number of whole chromosome sets—is an important evolutionary force in eukaryotes. Polyploidy is well recognized throughout the evolutionary history of plants and animals, where several ancient events have been hypothesized to be drivers of major evolutionary radiations. However, fungi provide a striking contrast: while numerous recent polyploids have been documented, ancient fungal polyploidy is virtually unknown. We present a survey of known fungal polyploids that confirms the absence of ancient fungal polyploidy events. Three hypotheses may explain this finding. First, ancient fungal polyploids are indeed rare, with unique aspects of fungal biology providing similar benefits without genome duplication. Second, fungal polyploids are not successful in the long term, leading to few extant species derived from ancient polyploidy events. Third, ancient fungal polyploids are difficult to detect, causing the real contribution of polyploidy to fungal evolution t...