Irish geneticists discover how some species may have survived mass extinction

Scientists at Trinity College Dublin have discovered how species may have re-emerged from mass extinction millions of years ago by strengthening their genetic mix.

They have unearthed what they describe as “a dramatic evolutionary event” in the ancient history of sturgeons and paddlefish that has significant implications for the way we understand evolution.

The geneticists outline how a species’ entire genetic make-up – their genome – is copied and pasted so that it suddenly has twice the genetic material it did before. This effectively provides a lot of raw material for mutations and evolution to occur – thereby facilitating its re-establishment.

They have pinpointed a process known as “whole genome duplication” (WGD) in the common ancestor of the sturgeon and paddlefish, which may have opened the door to genetic variations that conferred an advantage around the time of a major mass extinction 200 million years ago.

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Their findings suggest there may be many more overlooked, shared WGDs in other species before periods of extreme environmental upheaval throughout Earth’s tumultuous history.

The research led by Prof Aoife McLysaght and Dr Anthony Redmond from Trinity’s school of genetics and microbiology has been published in Nature Communications.

Prof McLysaght said: “Whole genome duplication is exactly as it sounds – it’s a fascinating evolutionary event where an entire genome is copied and pasted so that a species suddenly has twice the genetic material as it did before.

“We’ve know about whole genome duplication and rediploidisation for a long time but what is new, and exciting, is that we have shown that the time it takes for the second part of the process to complete is very important. In this case, it took a long, long time – so long that some gene duplications appear to be species-specific, occurring after the two species went their separate ways on the tree of life.

“As a result, the ancient original whole genome duplication that happened before the species had separated had been missed until now. We believe the same thing might have happened in many other species’ lineages and that is important given the possibility that it generated genomic conditions that helped the species survive mass extinctions,” she added.

Genetically, sturgeons and paddlefish show evidence of shared and non-shared gene duplications that were themselves derived from the ancient WGD, which, when timestamped to just more than 250 million years ago, places it just before the Permian-Triassic mass extinction that wiped out more than half of the families of all living things.

This would seem to add more weight to the theory that WGD events provide species with more of an evolutionary canvas to work with, Prof McLysaght said. More genetic material means more capacity for variations over a given time and that in turn increases the chances of conferring an advantage to cope with difficult or changing environmental conditions.

“Multiple whole genome duplication events famously occurred in our ancient early vertebrate ancestors and these have shaped the landscape of our modern human genome,” Dr Redmond noted. “Our findings are exciting because as well as shining a light on sturgeon and paddlefish genome evolution, they provide a comparative snapshot of how our early vertebrate ancestors genome and duplicated genes evolved after these doubling events.”

The research was supported by the Irish Research Council and European Research Council.