Cod supergenes in response to overfishing

Cod “supergenes” have shed light on how they respond to overfishing, and these supergenes may make them more resilient to other environmental changes.

This is according to a new study published by Norwegian scientists. This could be good news, as cod have a genetic architecture that will allow them to respond to climate change, but for now that’s pretty speculative.

For those of us who study the evolution of fish species under the strong selective pressure of commercial fishing, cod looks like a cartel. For example, scientists previously found that Northwest Atlantic cod showed signs of spawning at a smaller size or younger age before numbers plummeted.

The latest study looked at the current and historical genome (the complete set of genetic instructions contained in an organism’s DNA) of cod. Scientists have been particularly interested in areas of highly conserved “supergenes” and what they can tell us about these ecologically critical but highly exploited marine predators.


Supergenes are not additional unique genes as such

Rather, they are combinations of genetic material that are more conserved over generations. They are often tightly coupled or related and are responsible for a set of characteristics in an organism that are very important, such as the link between growth rates and reproductive capacity.

The authors found three conserved supergenes in cod off the coast of Norway. And the three supergenes were found in different relative abundance in two different populations of cod: inshore and offshore. This reinforces what we know about cod in the northeast Atlantic and that is a good thing, because if cod were a single spawning stock it would be more vulnerable to overexploitation.

An interesting consequence of this research is that scientists can combine their genomic approaches with knowledge of ancient stories and images, and records of fish bones and fishing gear found at archaeological sites, to reconstruct likely population sizes. cod around the world throughout history. Recent studies on several fish species have shown that the true benchmark of their abundance in European seas is likely to be underestimated.

In fact, this new analysis suggests that overharvesting of cod reduced their abundance several hundred years before modern commercial fishing began, and the signature of overharvesting is etched into their genome.

How Human Predators Switch Prey

In many different species, ahora recognizes that the populations are constantly changing, including changing changes in the physical tamaño, forming or rasgos as the tasa de crecimiento that is observed in solo unas few generaciones with significant consequences sober as the numbers fluctuate. Town.

Scientists recently updated a large dataset that now collects more than 7,000 examples of contemporary changes in biological traits of wild populations. The researchers examined whether observed trait changes, such as a change in average body size, were short-term and reversible, or whether they were more permanent and evolved responses to certain changes in the local environment, such as a increase in temperature or the introduction of a predator.

Their data clearly showed that higher and faster rates of trait change were associated with predation, for example, when a predator removes slower, smaller, larger, or less camouflaged individuals from a bird. a feral population, resulting in a change in direction to be smaller. , bigger or faster. These rates of change were particularly rapid when that predator was human.

adaptive evolution

Theories of evolution induced by human capture are now well established and there are many good examples where the selective capture of fish and game species has caused long-term changes, for example by influencing the behaviour, body shape or size and growth rates. sexual maturity.

I conducted laboratory research that showed both the likelihood that harvest-induced evolution could occur, as well as the likely impact that such a permanent genetic change could have on things like the size of resulting population or yields.

This area of ​​study is not without controversy, but it is now generally accepted that we must consider evolutionary selection pressure when using wild animals and plants as resources. As new scientific approaches and new opportunities emerge for examining the genome of wild animals, we may find more supergenes and the stories they can tell us about how organisms respond to the world in which they live.

This article was written by Tom Cameron, Lecturer in Ecology at the University of Essex. It is republished from The Conversation under a Creative Commons license. Articles in English

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