How do hybrid animals occur, from ligers to zores

In the summer of 2020, scientists in Pennsylvania noticed something no one had seen before: a bird that looked like a rose-breasted grouse’s beak but sang like a crimson tanner.

Upon careful analysis, the animal was later identified as a hybrid, the offspring of a mating event between two separate species.

“When I saw it, I said, ‘Oh my God!'” he recalls. ” Bob Mulvihill, ornithologist at the National Aviary in Pittsburgh. Mulvihill caught the bird and extracted a blood sample to study the genes of the hybrid animal.

While some animal hybrids are well known, such as the mule, this case was even more unusual due to the different colors of each bird species. grosbeaks rose breast Black and white with a red spot on their chest, while Cochineal tanning Bright orange and black. (Read more about the never-before-seen colorful bird hybrid.)

Birds are not exactly cousins, or even close relatives. Mulvihill suspects the species may have separated by more than 10 million years of divergent evolution.

Even stranger is the fact that these species coexist across much of their North American ranges, leading researchers to wonder why no one had ever seen evidence of interbreeding before.

Was this just the case of Romeo and Juliet? Laugh.

In the modern era of gene sequencing and genetic analysis, hybrid animals have taken on new importance and may hold clues that clarify the mysteries of evolution.

What are hybrid animals?

Genetically speaking, a hybrid animal is the result of interbreeding between dissimilar breeds, he says Erica Larsonan evolutionary biologist at the University of Denver.

Most non-scientists would consider this to mean breeding between two different species, but it could also include subspecies or even groups within a species that can be distinguished from one another based on certain traits or characteristics.

“They may breed at different times of the year, or they may have behavioral differences that make them less likely to mate,” Larson says. “But then, if they mate, they might make perfectly fine hybrids.”

One example might be the spotted skunk, which Scientists have recently divided into seven typesSome of them look almost identical and live in the same areas, but mate and give birth for months.

Another great example is coralLarson says. “A lot of corals release their gametes at a very specific time. So all of these species are physically in the same place, and maybe they can form a hybrid,” but they miss the opportunity by spawning hours or days apart.

In captivity or in the lab, these types of natural barriers are the least obstacle to successful crossbreeding.

What animals can crossbreed?

One of the most famous examples of crossbreeding is the so-called Tiger, A cross between a male lion and a female tiger. Ligers were raised to pop culture fame after a repertoire in movie 2004 Napoleon Dynamitebut few people have heard of tijunOffspring of a female lion and tiger tiger.

Both pairings are unlikely to occur in the wild because the lion and tiger ranges never overlap. The same goes for kamaLlama and dromedary Cross, which lives on opposite sides of the Atlantic, but was bred by researchers.

Horses can be particularly susceptible to crossbreeding. Donkeys and horses can breed to create mulesWhile making zebras and horses Zors or other groups.

In 2019, scientists demonstrated for the first time that The rhinoceros is sometimes crossed with beluga whalesresulting in a Narlog. There is also at least 20 reports on different species of dolphins and hybrid-producing whales In both the wild and in captivity.

And they are not just mammals. There are also documented cases of interbreeding between Wooden rattlesnakes and western rattlesnakesAnd the Cuban and American crocodilesAnd the Russian sturgeon and American paddlefishAnd the Trout and rainbow troutas well as in various insects, such as Ants, bees, wasps and termites. Plants are particularly capable of interbreeding and are believed to do so higher rates than animals.

Modern humans may be one of the most populous hybrid species on Earth, and they bear genetic markers for interbreeding with other ancient hominins, such as Neanderthals and Denisovans. (Read how You Might Have More Neanderthal Acid Than You Think.)

Are hybrid animals rare?

While the hybrids seem unusual, it is likely that many of them are very popular.

For example, Mulvihill says it’s probably no coincidence that crossbreeding is well documented the birdswhere huge 10 percent of the more than 10,000 known species are known to hybridize. It could be that there are so many bird enthusiasts who take pictures of interesting sights and then post them on forums, bird association pages, or smartphone apps like iNaturalist.

“Hybridization is certainly well known in butterflies as well,” Mulvihill says. But unlike birds, few casual observers of butterflies can easily detect signs of hybridization in insects.

Some scientists also believe that some types of hybrids may become more common in the future. For example, like Climate change shrinking Arctic sea icePolar bears are expected to spend more time on land, where they may encounter brown bears as they expand northward. If they mate, they can create hybrids known as pancakes or laughing bears. (Read why scientists expect more hybrids as the Arctic warms.)

Are hybrid animals good or bad?

Crossbreeding does not always mean genetic doom. But they may not produce stronger varieties either.

For example, ligers are prone to health problems, such as rapid growth and heart problems. (Learn more about ligers and other hybrid cats.)

Also, the parent species may have incompatible genetic differences, such as different numbers of chromosomes. This is one reason why hybrids are often sterile, and non-breeding offspring can limit the parents’ success in expanding their genetic pool.

“They have less chance of passing on their genes to the future generation,” Larson says.

Hybridization can be troublesome if one or both parent species are in danger of extinction. This is because when the genes of a species become scarce, the new combination of hybrid genetics can threaten its existence by replacing it. This is called genetic immersion, which is why crossbreeding is done with it coyote he is One of the many threats to red wolves right now in the southeastern United States.

However, crossbreeding can also introduce beneficial genes, such as resistance to pesticides, says Larson. If these genes help the hybrid survive and reproduce, these benefits could spread widely in the population. This is what scientists call adaptive introversion.

“But I think most of the time, it’s probably not helpful or harmful,” Larson says. “Most of the time, you probably don’t do anything.”

With advances in genetic tools, scientists can now look at the genome of a hybrid and easily identify overlapping genes that may have originated elsewhere. This means that each hybrid is a window into how evolution creates new species.

“When you have two species whose genomes have undergone independent evolution for hundreds of thousands of years, and then put them back together again, and you mix those two genomes into a hybrid form,” Larson says, “you’ll understand what works and what doesn’t.”

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