Synthesis: “The case of the missing ancient fungal polyploids”

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Matthew A. Campbell, Austen R. D. Ganley, Toni Galbadón, and Murray P. Cox

Fruiting bodies of a common field mushroom (Agaricus aestivalis).
(Credit: Austen Ganley)

Fungi often don’t get the same press as their more conspicuous cousins, plants and animals. But now they are the lynchpin in a new argument about the evolution of species diversity.

Polyploidy is the process that creates duplicates of existing chromosome sets. Many well-known species are polyploid, including wheat, coffee, lager yeasts, and salmon. However, it is in deep evolutionary history that polyploidy really gets interesting. The Japanese evolutionary biologist Susumu Ohno proposed that polyploidy events triggered major evolutionary transitions, such as the rise of flowering plants and the rapid dominance of early animals. His idea was that multiple copies of each gene in polyploid species provide genetic redundancy, allowing new functions to evolve and driving massive radiations of species.

These ideas now have some support: polyploidy events have been found at the base of many major evolutionary radiations in plants and animals. In this context, Campbell and colleagues point out that fungi are a conundrum: even though they have as many (or more) species as plants and animals, and although many major groups of fungi arose in bursts of rapid diversification, there is no evidence of ancient polyploidy events in their deep evolutionary history. So was Ohno right? If polyploidy didn’t drive evolutionary radiations in the fungi, was polyploidy really the driver in plants and animals?

In contrast, finding polyploidy events at the base of major fungal radiations would add critical support to Ohno’s original proposal. While several possible reasons might explain the observed lack of ancient polyploids in fungi, Campbell and colleagues suggest they may simply have been overlooked. They outline key reasons why polyploidy is difficult to detect in fungi, and importantly, propose how the scientific community might search for evidence of ancient fungal polyploids.

Perhaps it’s finally time for fungi to emerge from the shadows. Read the Article