Can someone explain what prevents birds of the same subtype from mating? The article mentions that the chromosome 2 cannot cross over in meiosis, but I just fail to understand the mechanics of the process and how that leads to disassortativity.
Having 2 copies of the mutated gene is probably deadly.
They are saying an individual can only mate with a quarter of the population, but it's obviously incorrect, as the pre-mutation birds can mate with both mutated and unmutated opposite sex.
The reason cross-morph pairs are observed more often as the mutated birds are more sexually aggressive and quickly round up unmutated opposite sex.
The article seemed to suggest that non-cross pairs are not observed at all, but they needed more genetic testing to determine if tan/tan never happens.
Even if the tan/tan is still physiologically possible it may be the case that they still won't mate even if there are no white present at all due to required mating signals being missing.
It's a common idea that evolution propagates useful mutations, and the non-useful disappear. How does it help a bird to have four sexes?
Or maybe it's just irrelevant for birds. Birds appear to break many laws of nature other animals have to abide by. They fly, they move where they want. They stay close to humans, observe them, and easily avoid them. They're amazingly energetic for how big they are. They migrate extremely far. They don't have to commit to anything except when rearing young.
> It's a common idea that evolution propagates useful mutations, and the non-useful disappear.
Common ideas are commonly wrong. Non-useful ones only disappear reliably if they're selected against. Otherwise, you get goose bumps, or piloerection in humans: We don't have enough hair over most of our bodies for erecting it to do any good, but we still have all the structures to erect it anyway, because none of our ancestors lost any of them even as they became useless.
By making procreation harder to achieve, you intensify the selection effect, since only the fittest individuals will be able to achieve it. So maybe it can be thought of as a kind of extra layer of "culling of the weakest" built into the genetics of the species?
More specifically, certain kinds of fungi have outrageous numbers of sexes, with a high degree of mating compatibility between them. https://www.nature.com/articles/6800035
It sounds like they're evolving into separate species.
Indeed it's one definition of a species that it's a population that can mate within it's group. So if they can no longer breed with each other, are they same species or not?
Before the invention of radio this was a property of language as well. Famously you could walk from Paris to Rome and every village could speak comfortably and naturally with its neighbors, yet by the time you got to Rome they spoke a language essentially incomprehensible to Parisians.
If I'm reading right, the two groups can only breed with each other. That is, white-striped males and tan-striped females can breed, as can white-striped females and tan-striped males. (And the offspring are about half white-striped and half tan-striped.)
So it's not speciation, any more than sexes themselves are speciation.
> white-striped males and tan-striped females can breed, as can white-striped females and tan-striped males
This alone doesn't contradict the two-species theory. It could be that white-M + tan-F is species #1, and white-F + tan-M is species #2. Sure, it sounds weird, but not nearly as weird as the idea of 4 sexes, IMO.
> (And the offspring are about half white-striped and half tan-striped.)
Now, this is the important part. As I understand it, the offspring of "species #1" could be "species #2" or the other way round. This indicates that #1 and #2 are the same species after all.
If the tan ones could only mate with the tan ones, that would work. As it is, though, no. A white male and tan female can have a tan chick that can go on to mate with a white bird (indeed must, if it mates at all). That’s not speciation.
Readit News
Discussion at the time: https://news.ycombinator.com/item?id=13027132
They are saying an individual can only mate with a quarter of the population, but it's obviously incorrect, as the pre-mutation birds can mate with both mutated and unmutated opposite sex.
The reason cross-morph pairs are observed more often as the mutated birds are more sexually aggressive and quickly round up unmutated opposite sex.
Even if the tan/tan is still physiologically possible it may be the case that they still won't mate even if there are no white present at all due to required mating signals being missing.
I.e., I would guess that plants that have easy seed propagation have less complicated sexes, but I don't know.
Or maybe it's just irrelevant for birds. Birds appear to break many laws of nature other animals have to abide by. They fly, they move where they want. They stay close to humans, observe them, and easily avoid them. They're amazingly energetic for how big they are. They migrate extremely far. They don't have to commit to anything except when rearing young.
Common ideas are commonly wrong. Non-useful ones only disappear reliably if they're selected against. Otherwise, you get goose bumps, or piloerection in humans: We don't have enough hair over most of our bodies for erecting it to do any good, but we still have all the structures to erect it anyway, because none of our ancestors lost any of them even as they became useless.
ie., evolution is starting with a bike and turning it into a car
it is not "starting with raw materials" and shaping them
So pretty much every life form is highly non-optimal wrt their environments.
By making procreation harder to achieve, you intensify the selection effect, since only the fittest individuals will be able to achieve it. So maybe it can be thought of as a kind of extra layer of "culling of the weakest" built into the genetics of the species?
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Indeed it's one definition of a species that it's a population that can mate within it's group. So if they can no longer breed with each other, are they same species or not?
So it's not speciation, any more than sexes themselves are speciation.
This alone doesn't contradict the two-species theory. It could be that white-M + tan-F is species #1, and white-F + tan-M is species #2. Sure, it sounds weird, but not nearly as weird as the idea of 4 sexes, IMO.
> (And the offspring are about half white-striped and half tan-striped.)
Now, this is the important part. As I understand it, the offspring of "species #1" could be "species #2" or the other way round. This indicates that #1 and #2 are the same species after all.