Species generally don’t interbreed into fertile offspring. Some species may be close enough in size and genetics to produce viable offspring, but there is too much mismatch in chromosomes to be fertile.
Other examples exist and are in fact more common, such as horse-donkey: we call it a mule when the father is a donkey and the mother a horse, or a hinny when the father is a horse.
Things are not always clear-cut in biology, but generally the species definition is that they can create offspring that in turn can procreate. Male ligers are sterile, so it doesn’t “break” any definitions.
See also mules: they are a hybrid of a donkey and a horse. Typically they are also sterile.
You said yourself that you know that the term species is kind of a blurry line. So while it’s usually true that members of different species can’t reproduce to make viable offspring, it’s definitely not a rule. A number of different but related species can successful produce offspring (which may or may not be fertile). Mules are famously a hybrid of a male donkey and a female horse. In fact, even humans interbred with other species. Humans extensively interbred with neanderthals to the extent that basically every human who isn’t from Africa has a few percent of their DNA from Neanderthal ancestors that bred with our human ancestors to produce viable, fertile offspring.
There are a number of mule/hybrid organisms, including the mule (horse/donkey offspring).
The limiting factor is how closely related the species is. The more closely related two species are, the more likely they are to have viable offspring. Usually the offspring is sterile (unable to reproduce with either member species) but on rare occasions they will be fertile.
What’s really fun are ring species. That’s where you have a range of closely related species that are geographically neighboring, and each species can breed with members of the neighboring species, but not any other members beyond those neighbors.
So if you have A | B | C | D | E in a circle (say a species of bird around one of the polar regions) and A and E are next to each other, then A can interbreed with E and B, B can interbreed with A and C, C can interbreed with B and D, and E can interbreed with D and A.
It’s worth noting that for breeding purposes, most dogs are essentially (modern gray) wolves and can interbreed with them. However far less common is a dog and fox hybrid, of which there is at least one known verified example.
Not really. Depending on how you define a species – specifically what’s known as the “biological species concept”, which is one of many – two animals are the same species if their offspring is normally fertile – that is to say, the child can go on to produce viable offspring as well. So ligers are hybrids and are typically infertile, so lions and tigers are different species. The same goes for mules, so donkeys and horses are separate species as well. Conversely, domestic dogs are a subspecies of the gray wolf, and the two can produce viable and fertile wolfdog children.
That being said, this definition doesn’t always hold. Coyotes and wolves are typically considered separate species, but their coywolf hybrid offspring are indeed fertile. There’s debate whether to consider neanderthals a separate species to ourselves or a subspecies of homo sapiens, because despite glaring differences the offspring of a neanderthal and a cro-magnon were indeed viable and fertile – we contain neanderthal DNA, some more than others. Some plants are very definitely hybrids and yet are fertile – oranges, for example. And this definition is very unhelpful when discussing, say, extinct species whose reproductive viability you cannot test, or creatures that don’t reproduce sexually or whose sexual reproduction is different to that of most animals (like how some fungi have dozens of different sexes).
Comments
some species can, mostly just closely related ones but they usually avoid it and the offspring is basically always infertile.
Species generally don’t interbreed into fertile offspring. Some species may be close enough in size and genetics to produce viable offspring, but there is too much mismatch in chromosomes to be fertile.
Other examples exist and are in fact more common, such as horse-donkey: we call it a mule when the father is a donkey and the mother a horse, or a hinny when the father is a horse.
https://en.m.wikipedia.org/wiki/Mule
Things are not always clear-cut in biology, but generally the species definition is that they can create offspring that in turn can procreate. Male ligers are sterile, so it doesn’t “break” any definitions.
See also mules: they are a hybrid of a donkey and a horse. Typically they are also sterile.
When a mummy tiger and a daddy lion love each other verrrry much…
Lions and tigers are both apart of the Panthera genus and have enough similarities that make them suitable for mating
You said yourself that you know that the term species is kind of a blurry line. So while it’s usually true that members of different species can’t reproduce to make viable offspring, it’s definitely not a rule. A number of different but related species can successful produce offspring (which may or may not be fertile). Mules are famously a hybrid of a male donkey and a female horse. In fact, even humans interbred with other species. Humans extensively interbred with neanderthals to the extent that basically every human who isn’t from Africa has a few percent of their DNA from Neanderthal ancestors that bred with our human ancestors to produce viable, fertile offspring.
There are a number of mule/hybrid organisms, including the mule (horse/donkey offspring).
The limiting factor is how closely related the species is. The more closely related two species are, the more likely they are to have viable offspring. Usually the offspring is sterile (unable to reproduce with either member species) but on rare occasions they will be fertile.
What’s really fun are ring species. That’s where you have a range of closely related species that are geographically neighboring, and each species can breed with members of the neighboring species, but not any other members beyond those neighbors.
So if you have A | B | C | D | E in a circle (say a species of bird around one of the polar regions) and A and E are next to each other, then A can interbreed with E and B, B can interbreed with A and C, C can interbreed with B and D, and E can interbreed with D and A.
It’s worth noting that for breeding purposes, most dogs are essentially (modern gray) wolves and can interbreed with them. However far less common is a dog and fox hybrid, of which there is at least one known verified example.
Not really. Depending on how you define a species – specifically what’s known as the “biological species concept”, which is one of many – two animals are the same species if their offspring is normally fertile – that is to say, the child can go on to produce viable offspring as well. So ligers are hybrids and are typically infertile, so lions and tigers are different species. The same goes for mules, so donkeys and horses are separate species as well. Conversely, domestic dogs are a subspecies of the gray wolf, and the two can produce viable and fertile wolfdog children.
That being said, this definition doesn’t always hold. Coyotes and wolves are typically considered separate species, but their coywolf hybrid offspring are indeed fertile. There’s debate whether to consider neanderthals a separate species to ourselves or a subspecies of homo sapiens, because despite glaring differences the offspring of a neanderthal and a cro-magnon were indeed viable and fertile – we contain neanderthal DNA, some more than others. Some plants are very definitely hybrids and yet are fertile – oranges, for example. And this definition is very unhelpful when discussing, say, extinct species whose reproductive viability you cannot test, or creatures that don’t reproduce sexually or whose sexual reproduction is different to that of most animals (like how some fungi have dozens of different sexes).