Rapid Evolution Through Defrosted Ice Age Genes

Some organisms - like this saltmarsh beetle - can evolve surprisingly quickly by re-using ancient gene variants that were once useful. (Image: RBINS)
04/12/2018
Rapid Evolution Through Defrosted Ice Age Genes
post by
Reinout Verbeke

Researchers of our Institute discovered that organisms can evolve surprisingly quickly by re-using ancient gene variants that were once useful. Understanding how species manage to adapt quickly is important in times of sudden changes in climate and environment.

A plant or animal usually evolves very slowly. You need new gene variants, and these can only arise through rare mutations in the DNA. Yet, biologists see that some populations are adapting very quickly to a new environment. This is the case, for example, with the saltmarsh beetle (Pogonus chalceus): individuals with long wings, who live in a swamp that is flooded once a year, evolve in barely twenty generations - in this case also twenty years - to a smaller short-winged type when they colonise a swamp that gets flooded daily.

Ice age

Researchers of the Royal Belgian Institute of Natural Sciences wanted to unravel the mechanism behind this remarkable observation and screened the entire genome of several populations of saltmarsh beetles. They were able to identify the genes underlying the rapid evolution towards the short-wing type. These genes turned out to be anything but new: by examining the variation in these genes, they saw that the gene variants for shorter wings originated some 200,000 years ago, during the second last ice age. At that time, an isolated population must have adapted over a long period to the tidal marsh in which they lived. They became smaller and developed shorter wings.

Sleeping genes

When the climate became warmer again, the short-winged saltmarsh beetles mixed with a long-winged population. As a result, the gene variants for short wings ended up in the gene pool of the long-wings. If these individuals now colonise tidal marshes again, they will carry all the necessary gene variants for shorter wings, so natural selection can very quickly produce a short-winged type. The ancient genes are in a sense reused.

This way, evolution can take place several times in almost identical ways, in different periods and in areas that are far apart. Unravelling the mechanism behind rapid evolution is important: it can help us to understand to what extent populations can adapt to climate change and habitat loss today. Some organisms can clearly do this very quickly. But the researchers stress that this is probably only the case if populations of that species have adapted to identical conditions over a long period of time in the distant past, and if the old gene variants that have arisen as a result are still present in the gene pool. 

Toolbox

‘Everything that lives inherits a large toolbox from generation to generation', says evolutionary biologist Frederik Hendrickx (RBINS). 'It contains many old tools that have proven their worth in a certain period and time but are no longer used today. But those old chisels and screws can suddenly prove useful again, even vital.' Humans are no exception: 'We too can still carry ancient gene variants that could one day determine our success in existence.'

The study was published in in PLOS Genetics.

 

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