Can hybridization protect species from extinction in the face of climate change?

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Creating hybrids could make animals more resilient to global warming, but it could also lead to a complete loss of the original species. 

The Houston Ship Channel is known as the busiest seaport in the world and also a home full of trash and toxic chemicals. But the Gulf killifish has found a way: it has evolved resistance to pollution by crossbreeding with another species, the Atlantic killifish, which happens to produce a useful mutation.

Hybridization between species has been and is taking place in nature 

Crossbreeding or crossbreeding in the wild is more common than we think. As global warming causes animals to move to areas with lower temperatures, many species decline together. In Alaska and Canada, grolar bears have been spotted as a result of grizzly bears (silver heads) moving into polar bear territory to escape the heat. 

Recently, conservationists have proposed the idea that we can breed animals for their own sake. Like the Gulf killifish’s new pollution defense, they think crossbreeding could give the vulnerable animals an evolutionary jump-start in the race for genetic adaptation. transmitted with global warming.

Their tolerance to higher temperatures or acidic ocean environments is improved. Others are also wary of the increasing loss of species over millennia as they are mixed with different animals. This debate presents a huge problem in conservation, centered around a big question: can we protect animals while forcing them to change?

A grolar bear in captivity

Michelle Marvier, a conservation biologist at Santa Clara University in California, says a lot of things are always hybrid, it happens in plants, fish and amphibians, even some animals mammal. In fact, many of us already carry traces of different races in our DNA, proof that we have mixed with other human species. It could be something that led to an evolutionary end because the progeny were infertile or another way to adapt to the evolutionary process.

This aspect is attracting the attention of researchers. For species with long intergenerational periods, there is little chance for beneficial mutations to arise, so if the environment changes rapidly, normal evolution may be too slow. for those animals to adapt and survive. Hybridization can provide a shortcut by rapidly introducing genes from outside the normal gene pool.

Madeleine van Oppen, an ecological geneticist at the University of Melbourne, says that when it comes to crossbreeding between different species, the real driving force is to create new combinations of genes and increase genetic diversity. That diversification will increase the likelihood of new adaptations that could save species from extinction due to global warming, like the Gulf killifish that have been saved from pollution by mutations in the Atlantic killifish. He also worked on coral reefs, half of which have disappeared in the past 30 years, largely due to global warming. By crossing corals in the lab, she created new hybrids and tested them to see how they held up in warmer conditions. She and her colleagues have shown that some hybrid corals survive up to 34% better temperature and CO pressure than their parents.

But what is the downside of crossbreeding?

However, not all species are bred and tested in a laboratory. Instead, conservationists can move one species into the habitat of other species and expect them to continue to breed. Although no one has yet attempted to create climate-resistant hybrids in this way, the method has been used to combat inbreeding in species with only a few individuals left. .

The Florida newspaper is a prime example. In the mid-1990s, when there were only about 25 left and scientists thought they would become extinct within two decades. As a last-ditch effort to save them, conservationists moved eight Texan cheetahs into their habitat to boost genetic diversity. There has also been much debate about this action. Thirty years later, there are still leopards in Florida, but many people doubt whether it will still be a Florida leopard if you bring leopards from Texas to cross with them. 

A European wildcat in Glen Feshie in the Scottish Highlands

The worry here for those interested in forcing an endangered species to breed is that instead of saving it, you’ll do the opposite: make it extinct. Why, since its genome ceased to exist in its original form, the genes of the newcomers eventually corroded the genes of the original “residents”, leaving no trace of what had caused they become special.

That’s also what some European feral cats have to deal with. In Scotland, there are only a few hundred left, and a 2019 report by the International Union for Conservation of Nature found that the main threat to them is crossbreeding with domestic cats. The report also says the animals currently roaming the Scottish Highlands are primarily a “hybrid pack” of wild cats with varying degrees of domestic crossbreeding.

The same situation is happening in the Jura mountains of Switzerland. Wildcats have a few domestic genes “it’s not a big deal if they can survive and interact and play their ecological role”, but now the Jura wildcat will become physically indistinguishable. genetics with domestic cats within a century. Who knows what happens after that, widespread crossbreeding can lead to loss of ability to adapt to the local environment. occurred with the scalloped trout in the Rocky Mountains of North America, an iconic animal that is the fish of seven states in the United States.

Ecologists say native salmon have adapted to survive in the face of extreme environmental change over time: floods, wildfires, frost. But when they crossed with invasive rainbow trout, which produced millions of fish released for fishing in the 20th century, the set of genes responsible for those adaptations was disrupted. This, it is predicted that with new bad combinations of genes, has further adverse effects on the generation lines. For rainbow trout, for example, crossbreeds produce fewer and fewer offspring with the rainbow trout ancestor they have more of. With as little as 20% crossbreeding you should see at least a 50% drop in fitness and this pattern has been seen in different populations.

Predatory Salmon in the Pacific Northwest of America

Anything has to have a trade-off

It is therefore understandable to be wary of human-facilitated hybridization. But conservationists argue that such dire scenarios are rare. Because, as they said at the outset, most introduced species are completely benign. In a recent review, it was found that while many studies highlight “invader” crossbreeding as a threat to native species, only a few provide evidence. facts about harm, such as poor growth or fertility. If a native species is altered, but in an adaptive way that works in its ecosystem, that is not necessarily considered a loss.

Ecologist Daniel Simberloff at the University of Tennessee says that in the field, he is amazed at the very distinctive and idiosyncratic adaptations that different species have developed. He thought that he could not be encouraged by what many people talked about as an alternative. The last thing biologists want is to have so many gene lines that we lose the uniqueness of the species we’re trying to protect. 

In the view of some, we would ideally keep all species exactly as they are, but we should no longer be allowed to “luxury” because the environment is changing at breakneck speed. and biodiversity loss happens too fast. In other words, if we can’t save the species we have, maybe we can help nature create new species that are more likely to survive.

Such trade-offs are also not necessarily man-made, but occur in nature. Female Plains toads that live in the New Mexico desert, for example, prefer to mate with a Mexican pickaxe, but only when their pond is dry. Hybrid tadpoles grow faster and have a better chance of reaching maturity before the water disappears. However, it is a difficult choice as only female crossbreeds are able to reproduce. 

Pfennig, who studies ornithology, suspects hybridization plays a big part in why Plains penguins migrated from their ancestral grasslands to the desert, because it may have allowed species move to new habitats they would not otherwise be able to live there. It’s probably not a giant leap to think that it could do the same for species that find themselves in new or severely altered environments by global warming.

The technique of hybridization, if it is to become widely available, requires great caution

Genome tuning using hybridization is said to be “a really blunt tool”. It’s like using a sledgehammer in surgery, while gene editing gives us much more control. A prominent case is the American chestnut, the plant of which was widespread until an imported blight fungus inadvertently infected them. People have been trying for a long time to cross breed American chestnuts with resistant Chinese chestnuts, which have also grown. But scientists have now managed to match American chestnuts with a wheat gene that makes them resistant to drugs, which is likened to using a scalpel in surgery, not ” drop hammer”.

Evolutionary biologist Andrew Whitehead, who studies Gulf killifish, doesn’t see this as a viable option for most species. He thinks we’ve written too little about how this change or gene insertion will affect animals when they’re out in the wild. He thinks it’s foolish to think we can genetically engineer a future organism.

However, evolution also wouldn’t be able to do the job without our help. People often take the Gulf killifish story to mean that evolution will provide solutions to pollution and global warming. But this is considered an exception. Experts note, we need to act from the source of the problem, which is climate change. While this may sound convincing, some damage has actually occurred and is difficult to reverse. Now you just have to look and the leopard population in Florida, they have plummeted due to road accidents and their food prey has disappeared. But there’s an even bigger problem: Florida is sinking. Which brings us right back to the hard question: if we can’t save them as they are,

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