There is a fish in the Houston Ship Channel. It is one of the busiest ports in the world and all the traffic has made the water slick with toxic chemicals. The Gulf killifish has found a way to adapt to pollution by cross-breeding with the Atlantic killifish.
As global warming makes animals move to areas with lower temperatures, more species may get thrown together, and cross-breeding is more common in nature than we used to think. In Alaska and Canada, people have spotted grolar bears, the result of grizzlies moving up into polar bear territory to escape the heat.
We could cross-breed animals for their own good. They think that hybridisation could give vulnerable animals an evolutionary head start in the race to genetically adapt to global warming. Their tolerance of higher temperatures could improve.
Some are wary of losing ancient species as they are mixed with different animals. The question of can we protect animals while forcing them to change is the subject of this debate.
"Lots of things hybridise all the time," says Marvier, a biology professor at Santa Clara University. It happens in plants and animals. Many of us have traces of Neanderthals and Denisovans in our genes, which is proof that we mixed with other human species.
The second aspect is drawing interest. If the environment is rapidly changing, normal evolution will probably be too slow for animals that have a long time between generations. The genes from outside the normal gene pool could be brought in quickly by hybridisation.
Madeleine van Oppen is an ecological geneticist at the University of Melbourne. The Gulf killifish was saved from pollution by the Atlantic killifish, because of their diversity.
As it stands, Jura wildcats will become genetically indistinguishable from domestic cats within a century
Half of the corals that have existed over the last 30 years have disappeared due to global heating. She crosses corals in the lab to create new hybrid offspring to see how they hold up under warmer conditions. She and her colleagues showed that some coral hybrid children were better off than their parents at higher temperatures and CO 2 pressure.
Not all species can be tested in the lab. One species could be moved into another's habitat and hope they breed. The approach has been used to combat inbreeding in species with only a few individuals left.
The Florida panther is an example. Scientists thought they would become extinct in two decades. It was a last-ditch attempt to save them, and there was a lot of debate and angst over what that would mean. Is it still the Florida panther if you bring in panthers from Texas to interbreed with them?
The worry with forcing a threatened species to hybridise is that you will make it go extinct. The original form of its genome is no longer valid. The genes of the newcomers swamp those of the original inhabitants, leaving no trace of what made them unique.
Some of Europe's wildcats face this. In Scotland, only a few hundred remain and the main threat to them is cross-breeding with domestic cats. The report says that there is a swarm of wild cats with different degrees of domestic hybridisation in the Scottish Highlands.
The situation in the Swiss Jura mountains is similar to that in the rest of the world, according to Juan Montoya-Burgos. He and his colleague have shown through modelling that a few domestic genes are not a problem if they are able to survive and interact.
How they will fare is anyone's guess, but we know that extensive hybridisation can result in loss of adaptation to the local environment. The cutthroat trout is the state fish of seven US states, and it appears that this is happening to it.
Clint Muhlfeld from the US Geological Survey says that native trout have adapted to survive in the face of extreme environmental change. The collection of genes that are responsible for those adaptations are broken up as they breed with the rainbow trout.
Bad new gene combinations and this could have detrimental effects further down the line. The more rainbow trout ancestry a hybrid has, the less offspring they produce.
It is understandable to be wary of human-facilitated hybridisation. She says that most introduced species are perfectly benign. In a recent review, she and her colleagues found that while many studies highlight hybridisation as a threat to native species, few produced actual evidence of harmful effects, such as poor growth or fertility. The paper argues that if a native species is changed, but in an adaptive way, it should not be seen as a loss.
Daniel Simberloff is an ecologist at the University of Tennessee. The last thing we want is to have so much flow of genes that we lose the distinctiveness of the species we are trying to protect, says Pfennig.
We don't have that luxury anymore because the environment is changing so rapidly and we don't know how long it will last. Maybe we can help nature make new ones that are more likely to survive if we can save the ones we have.
I think we’re fools to believe that we can genetically engineer a future-proof creature
There are trade-offs in nature. Female Plains spadefoot toads living in the New Mexico desert prefer to mate with a Mexican spadefoot if their pond is drying out. Before the water disappears, hybrid tadpoles have a higher chance of reaching adulthood. Only the hybrid daughters are fertile, so it is a hard choice.
The Plains spadefoots moved from their ancestral grassland to the desert because of hybridisation, which allows species to move into new habitats that they otherwise wouldn't be, according to Pfennig. It's not a big deal to think that it could do the same for species that find themselves in altered environments due to global warming.
Simberloff says that adapting genomes using hybridisation is like using a sledgehammer in surgery. The American chestnut was a widespread plant until it was accidentally imported with a disease.
He says with a hand held next to his chest that people have tried to hybridise the American chestnut with the Chinese chestnut. Simberloff's surgery analogy is the scalpel.
The Gulf killifish is not a viable option for most species according to evolutionary biologist Andrew Whitehead from the University of California, Davis. He says we don't know enough about how changing genes will affect animals.
He says evolution won't do the job for us. The story about the Gulf killifish is an exception, so it is wrong for people to think that evolution will solve pollution and global warming. We know that it will work.
It is hard to disagree. It is impossible to protect all but the most charismatic and important species at the same time.
Some damage has already been done and will be hard to reverse. Take Florida. The population of panthers has plummeted due to road accidents and disappearing prey, but fixing that might not even matter in the long term.
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