Why does polyploidy give an evolutionary advantage?

Question

I would like to know what advantages polyploidy holds. I have come across a few examples during my research of polyploidy, for example human adults' hearts contain 27% diploid, 71% tetraploid and 2% octaploid nuclei, Deinococcus radiodurans can have up to 10 copies of genome, and most of the plants consumed by humans have more than 2 copies.

I have no source of any sort for these, but I think they could be advantages:

• One of the most obvious one would be resistance to more physical effects.
• In the case of plants it might be the increased need for protein construction during the development of the seed.

What I would like to ask is whether the ones I wrote are correct, and if there are any other possible advantage.

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I have read similar questions but could not find what I was looking for.

Answer 1

First of all I am not sure if your examples are per se correct. But they might also be an additional bonus. Secondly, I would like to refer to two articles: "Polyploidy" and "The advantages and disadvantages of being polyploid".

One of the main benefits could be allowing organisms long-term evolutionary flexibility. Often adapted polyploids can undergo a proces that is called diploidization, during which genomic redundancy is removed. This means extra copies of genes will undergo less negative selection. Meaning alleles containing deleterious mutations at functionally important nucleotides are selected against. This allows more mutational freedom, leading to what is called subfunctionalization and neofunctionalization: new genes are created with slightly different or new functions. Other redundant genes are lost or become inactivated (pseudogenes).

Another example of benefits from polyploidy, this time not in an evolutionary, but in a more individual context, is the fenomenon called hybrid vigor or heterosis. Heterosis is a phenomenon in which a polyploid offspring of two diploid parents is more healthy and vigorous than its progenitors. One of the factors explaining this could be due to a protection against recessive characters, as being homozygous as a polyploid is even more 'uncommon'.