Hybridization, a much more common phenomenon than it seems

According to several scientists, certain hybrid animals could become more common in the future. With global warming, the surface area of ​​the Arctic sea ice is decreasing, forcing polar bears to spend more time on land, where they could encounter brown bears moving north. If they were to mate, they could produce hybrids called pizzlies or grolars.

If this phenomenon is not synonymous with genetic disaster, it is not likely to produce more resistant species either.

Ligers are, for example, prone to health problems and suffer from rapid growth and heart problems in particular.

“Parent” species may also have incompatible genetic divergences, such as a different number of chromosomes. This is one of the reasons why hybrid animals are often sterile, and offspring unable to reproduce can limit one parent's chances of spreading their genetic heritage.

“They have one less chance of passing on their genes to a future generation,” emphasizes Erica Larson.

Hybridization also poses a problem if one or both parent species are in danger of extinction. When an animal's genes become rare, they risk being replaced by a hybrid's new combination of genes. Called genetic pollution, this phenomenon is why interbreeding with coyotes is one of the main threats to red wolves in the southeastern United States.

Hybridization can, however, introduce beneficial genes, such as those for resistance to pesticides, specifies Erica Larson. If these genes help the hybrid animal survive and reproduce, they could spread within a population, a phenomenon called “adaptive introgression.”

“But most of the time, it’s neither beneficial nor detrimental. It probably has no impact,” adds the biologist.

Thanks to advances in the field of genetics, scientists can now study the genome of a hybrid to easily identify intruder genes. Each hybrid is therefore a window open to evolution and the way in which new species are born.

“When you have two species whose genomes have evolved independently over hundreds of thousands of years and you put them together and mix them to make a hybrid, you understand what works and what doesn't,” concludes Erica Larson.