Some basic science in these trying times? Let me try to explain why this freshly posted preprint by @rshanburns, @Polina_Novik and me might be of interest to anyone with polyploid ancestry!
Gradual evolution of allopolyploidy in Arabidopsis suecica https://www.biorxiv.org/content/10.1101/2020.08.24.264432v1

Indeed most organisms have polyploid ancestry, and it is highly plausible that this has played a major role in evolution by giving it genome-wide redundancy to play with. This is strongly suggested by the non-random stretches of duplication that remain. But how does it happen?

All sensible people agree that speciation is a process, not an event. But what about polyploidization? It could, in principle, instantaneously create an individual reproductively isolated from its kin. A bona fide speciation event, with an actual Adam and Eve, as it were.

Moreover, how does one cope at the cellular level? Good question, and very sensible people have suggested that there might be an immediate "Genome Shock", with massive changes to structure and regulation, transposons running amok, etc. Much drama.

To gain insight into the process of polyploidization, we need to see it in action, i.e., look at species that recently underwent polyploidization. Most such species are plants, and most work has been done on crops (which may not be very typical).

We looked at A. suecica (As), a ~16 kyr old natural polyploid generated via a cross between A. thaliana (At) and A. arenosa (Aa), two parents separated by ~ 6 Myr and differing in everything from chromosome number and genome size, to mating system and ecology.

We knew that there was no Adam and Eve: although there was a strong genetic bottleneck, there were many crosses and polymorphism is shared with the parental species. But what about the Genome Shock? @rshanburns spent Stakhanovite years looking for and this is what he found...

1: Massive genome rearrangement?

Nope. The genome is almost perfectly perfectly co-linear with the parent species. No major rearrangements, no massive gene losses.

2: Nucleolar dominance? It was observed long ago that hybrids tended to express rRNA from one species only.

Nope. Varies between individuals. Since @malacopa_genome found that rDNA cluster silencing varies within At, the phenomenon is probably unrelated to hybridization.

3: Subgenome dominance?

Nope. As befits a species named after , both parental genomes contribute equally to offspring expression, and there is no kinky stuff.

4: Transposon mayhem?

Nope. McClintock may have given a speech in Stockholm, but As didn't listen, and there was no revolution. Transposons are jumping normally, including between subgenomes, and integration appears to be proceeding smoothly. Very .

OK. Fine. No . So what is there? Surely something is happening, even in ? Indeed: comparing the expression of each subgenome to the parental species, we see clear changes that suggest gradual adaptation to being polyploid.

For example, the At subgenome has increased expression of genes related to meiosis, perhaps because the As genome is nearly 3x as large? And the Aa subgenome has increased expression of genes involved in interaction with the plastids, perhaps because these were inherited from At?

Not all is stasis at the genome level either. We found instances of double crossovers between homeologous regions of the two (very different) subgenomes, so that some As individuals carry 4 copies of the genome from one parent species (and 0 from the other) for several Mb.

This is interesting because 100's of species-specific genes may be lost in the process. Perhaps they were not needed, and that's why they were species-specific in the first place? So many questions...

In conclusion, we would suggest that the absence of is no accident, but rather a consequence of natural selection. "Natura non facit saltum." Artificially created As often do show reduced fertility and other evidence of a Genome Shock. How does evolution get around this?

So many questions! We are confident that we can learn much about both genome evolution and function from studying polyploidization. And not only in As, obviously, as we have no idea how typical it is. Thanks for reading!