When Three Species Combine: Multi-Species Hybrids

When Three Species Combine: Multi-Species Hybrids

This episode is sponsored by Skillshare. [♪ INTRO] We generally think of species as discrete
groups of organisms that simply can’t interbreed. But hybrids, the offspring of two species,
do happen. And they can be very useful. Take mules, for example, the offspring of
a male donkey and a female horse. They’re bigger than donkeys and hardier
than horses, making them helpful pack animals. But they’re also sterile, and that’s because,
well, mixing species usually doesn’t work. And that makes it all the more surprising
that there are cases where three or more species come together. These multi-species hybrids are really rare, but they can teach us a lot about
the inner workings of genomes. Most of the time, cross-species mating isn’t
fruitful because for an embryo to survive and develop, there has to be
enough consistency between its parents. The sperm has to be able to recognize and
fuse with an egg, for example. And even if an embryo starts developing, you
still have the issue of incompatible genes. To really simplify it, you can think of different
genes in a genome as a sports team. Over time, players start to work really well
together and the team plays better overall. But if you take those players
and stick them on other teams, they don’t always perform as well,
and in some cases, they can completely clash with their new
teammates, making the whole team struggle. It’s basically the same idea with cellular
machinery, except that inter-gene clashes can’t be solved with a mid-season trade. All of these barriers make it
unlikely for hybrids to occur, and even more unlikely that such hybrids
will produce their own offspring. But sometimes, they do just that. In the summer of 2018, for example, a keen-eyed birder
discovered a 3 species hybrid warbler in Pennsylvania. Warblers are small, often colorful birds that
sing pretty songs, hence the name. This bird looked kind of like a golden-winged
warbler, but was singing like a chestnut-sided warbler. Ornithologists sequenced some
of the bird’s mitochondrial DNA, the DNA that lives in the cell’s energy factories,
and almost always comes solely from the egg, as well as some parts of its regular genome. And it turned out to be the offspring of a
hybrid female, herself the result of a golden-winged warbler and a blue-winged warbler mating,
and a male chestnut-sided warbler, which is in a different genus from either of the hybrid
parent species. This odd pairing probably occurred because
the female couldn’t find a more closely related mate. Ornithologists already knew that
warbler populations weren’t doing so hot, so this is seen as more evidence that
population declines are significant. But it also adds support to the idea that
warblers are a rapidly evolving group where species split off behaviorally long before
their genomes become incompatible. Studying such groups can help scientists understand
what factors cause species to diverge and what exactly makes genomes incompatible. Now, this hybrid warbler isn’t the only
multi-species hybrid you might see if you live in the eastern US. It used to be that wolves were the
big canine predators in the northeast and coyotes were the top dogs in the southwest. But almost a century ago, people started to
see what appeared to be coyotes moving eastward. These weren’t coyotes with wanderlust, though,
they were coywolves: hybrids between coyotes and wolves. And they’re one of the most clear examples
of a phenomenon called hybrid vigor. Like I said, usually, mixing the genomes of
different species fails. But sometimes, it can more than work,
creating an animal that’s better in some ways than one or both of its parents. Wolf attributes like large size and wider
skulls made coywolves better at hunting large prey than their coyote parents, which allowed
them to basically take the ecological place of wolves in areas where humans had hunted
them to near-extinction. And it isn’t just wolf genes helping coywolves succeed. Researchers in 2014 looked at lots of individual
mutations in their genomes, what geneticists call single-nucleotide polymorphisms or SNPs,
and found that coywolves are actually a hybrid consisting of two wolf subspecies, coyotes,
and dogs. So, maybe you should call them coy-dog-olfs
or something like that. Since dogs are so well-adapted to living with people, blending them into the mix might have helped these hybrids adapt to human-dominated environments, like the towns and cities that have sprung up
on what long ago used to be wolf territory. And by studying how the genes
from all these species interact, these hybrid canines are helping
geneticists understand how mixing genes from multiple
species can help organisms survive, something that happens all the time in plants. Unless you’re avoiding gluten, you probably
have a 3-species hybrid in your pantry. Common wheat, which supplies
roughly 20% of the world’s calories, is actually a hybrid between 3 species of grass. And its multi-species origin is
probably what made it so useful to us. Sometime roughly 300,000 to 500,000 years ago, two wild species of grass hybridized,
but in a remarkable way. The hybrid retained both complete sets
of chromosomes from its parents, literally, twice the amount of DNA. Humans soon domesticated that hybrid, known
as Emmer wheat. Then, around 10,000 years ago, it crossed
with another wild wheat species, resulting in modern wheat which has
complete chromosome sets from all three of the species that went into it. Now, in most animals,
having extra sets of chromosomes, what geneticists call being
polyploid, is a big problem. That whole incompatible players thing applies
even more so with extra genomes. Yet, for reasons that remain elusive, plants
seem to be able to handle way more genetic weirdness, so polyploidy is
much more common in them. And having all those redundant genes turns
out to be pretty useful when you want to get a plant to evolve a particular trait through
selective breeding. There’s just that much more genetic material
that can mutate without killing the plant. Even if a particular mutation isn’t super
helpful, there are backup copies of that gene which ensure all the necessary things still
happen, allowing individual genes to be more flexible. So being a polyploid, 3-species hybrid is probably what allowed us to breed
wheat to have traits we really like, like seed hulls that fall off the kernel
more easily so they’re easier to process. By studying wheat and other multi-species hybrids, scientists can gain a clearer understanding
of what works genetically and what doesn’t. Whether they’re grasses, mammals, or birds, these species mash-ups are helping
unlock the mysteries of the genome, and that could lead to everything from
better crops to improved gene therapies. Multi-species hybrids show us how bringing together
different things can create something special. And that’s also true in photography. I love the way double exposure photos bring
together two or more completely different images to create a stunning work of art. This effect can be created with
photo editing software, but these neat dual images have
been around much longer than that! And photographer Tabitha Park
has a class on Skillshare which shows you how to make them
the old-school way: with your camera. In this class, she shows you three different
methods for creating photo overlays. What I like most about it is that her instructions
are so clear and easy to follow. She’s one of Skillshare’s top teachers,
which means her classes are high quality and she’s an engaged teacher. Students receive thoughtful feedback on their class projects and she’s available to
answer questions you may have. If you want to take your
photo game to the next level, you can check out some of her other classes,
which cover all sorts of photography tricks from creating amazing backdrops
to how to edit using Lightroom. And there are tons of other great teachers
on Skillshare, too. Right now, Skillshare is offering SciShow
viewers 2 months of unlimited access to their over 20,000 classes for free! So you can take some great photos,
cook a new kind of cuisine, or learn something else new,
all while supporting SciShow. You can follow the link in the description
to check it out for yourself! [♪ OUTRO]

41 thoughts on “When Three Species Combine: Multi-Species Hybrids

  1. No mention of the freaky fish family Poeciliidae (platies, mollies, swordtails, and guppies). They all can cross with Platies but they can't cross with each other. For example, a molly, a swordtail or a guppy can cross with a platy, but a molly, a swordtail or a guppy cannot breed with each other. The offspring are all fertile, and can breed with all of the others also producing fertile offspring. So you could very easily make a four species hybrid without even trying.

  2. Whilst I hate to pin holes in a science show which may or may not know more than I do, however what I've been taught from scientists that I have met in my field of work, which is canine based, is inconsistent with what is being told here.
    1. species are defined as creatures with dna similar enough to create fertile offspring, if two creatures mate and then their offspring also mates, then the original two individuals were of the same species.
    2. dogs are within the same species as wolf but are a subspecies, they are "canis lupus familiaris" whilst wolves are "canis lupus".
    I am very confused as to why there's this inconsistency so if someone could point me to a properly sourced link that can clear up this confusion and tell me what's actually right, I would really appreciate it.

  3. Life will find a way? Humans have trashed the planet, we will likely wipe ourselves out in the process, then all the life that survives us will have a huge party. In the meanwhile, it seems like there are some swingers parties going on on the down low right now!

  4. Obviously, we need to be more careful in declaring different-looking populations as separate species.
    Case in point: Domestic dogs. Chihuahuas vs Great Danes – Same species.
    Maybe those warblers were not really different species?
    Maybe we're really the same species as Neanderthals? – We weren't separated long enough to evolve sufficiently different genomes that could no longer interbreed successfully.

  5. My school instructor is the warbler's discoverer's wife. My class knew about the warbler months ago. Amazing to know we learned about a 3 species hybrid before it was so well known.

  6. this episode excites all my childhood dreams in me and im just giggly because the words (multi-hybrids, mutations, adaptations) really gets me going. Awesome episode

  7. I find it strange that a lot of english speaker ( especially american) are making their voices "crack " at the end of the sentences. Boh

  8. People making jokes but the warbler was so sad. It's like a human not being able to find a mate and went with a Lucy-like species.

  9. Iโ€™ve lived on the east coast of the us for my entire life, Iโ€™ve never seen a wolf but coyotes are everywhere. You can hear them making noises in the woods during summer… maybe they are hybrids..?

  10. I can name a plant hybrid that occurred naturally, that you've probably encountered in some form today: peppermint. It's a cross between spearmint and the lesser-known watermint. I had always considered the milder spearmint to be an offshoot of the sharper peppermint, but it turns out it's the other way around (and if you think peppermint is strong, you should try watermint!).

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