For any species with such a tiny population, long term survival can be a crapshoot. They’ve already been down to two individuals, and another drought could wipe them out entirely. But if they can build their population up to a reasonable number, they could persist on Daphne Major for some time.
If they didn’t reproduce with the one parental species on the island when they were down to very low numbers, they probably won’t now. (The other parent came from an island 100 km away so that’s not a potential partner). So I don’t think they will be wiped out by hybridization.
However, Daphne Major is only about 2 square miles in area. This is probably too small to support a viable population indefinitely. (The other finches on the island also occur on larger islands in the archipelago and can recolonize if they become locally extinct). Long term survival probably depends on colonizing the much larger neighboring island of Santa Cruz, and being able to exploit a resource there that is not already being used by another finch. Offhand, I don’t know if there is a finch species on Santa Cruz of similar bill size that might exclude a colonist.
I’ve never been entirely comfortable calling the results of polyploidy in plants a new species, since they can just as easily change their number of chromosomes in the other direction, and re-join the original species. Speciation, it seems to me, should be more permanent than that.
On the other hand, a new species branched off of H. sapiens a mere 60-something years ago, and it’s unlikely that H. hela will be rejoining H. sapiens.
[From Wikipedia](https://boards.straightdope.com/sdmb/A species is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction.):
Also, there are lots of immortalized cell lines, HeLa isn’t unique other than having had a popular book written about it. And if you conciser immortalized cell lines to be new species, you need to conciser each and every metastasizing cancer to be a new species.
There are plenty of immortal cell lines that live in carefully-controlled environments with sapient humans providing everything they need. But HeLa cells live in environments which are not only not deliberately hospitable to them, but actively inhospitable, in that laboratories have tried to clean them out of their equipment and failed. That, to my eyes, qualifies them as independent organisms, in a way that other cell lines don’t.
Cite? By what mechanism would a polyploid become converted to a diploid? Assuming a tetraploid, meiosis will reduce the gametes to the diploid number (rather than haploid, as usual). How do you get it down to haploid so that mating will get back to the original diploid number? Whatever the mechanism, reverting back to the original number is going to be much more difficult than simply multiplying it.
In any case, you seem to be talking about autopolyploidy, in which the chromosome duplication takes place in a single species. But many cases of polyploidy involve allopolyploidy, in which the sets of chromosomes come from crossing different species. These latter certainly can be considered a new species, since they will usually be different from both parental species and unable to backcross with either of them.
Polyploidy is very common in plants. According to some estimates, between 30-80% of all angiosperm species are of polyploid origin.
Hm, OK, there are a lot more of those than I thought, some of which also have many different entries. HeLa seems to be the most widespread, by a fair margin, but that might just be an artifact of it being the first one isolated (thus having had the most time to spread, including time before the contamination issue was recognized).
I would imagine there is a point where two lineages can still interbreed (goats and sheep? Lions and tigers?) but the likelihood of the fetus surviving to term becomes less and less as the general DNA and the “instructions” included on each branch become more and more conflicted. Eventually, the two lines are completely incompatible. However, this won’t happen if there is regular interbreeding which is why distance or ecological niches usually cause species to differentiate.
Based on the different species that can reproduce, I would suggest the differentiation using natural methods would take a very very long time.
The trouble with directed evolution (animal husbandry) is that often it emphasizes some characteristics at the expense of others. Many pure-bred dogs are high-strung morons, since survivability and smarts are not selected for, while for a species in the wild there’s a basic bar to clear. Plus - for a sheep dog, for example, you can’t afford to throw away herding capability in favour of a pretty coat pattern. Modern cows and pigs, for example, have been bred for their productivity also at the expense of basic intelligence.
In the wild, a species is usually - how evolution works - well adapted to its environment, the mix of environmental pressures that they can accommodate. Changes to a species are either drift - changes in characteristics irrelevant to survival - or in response to changes in the environment it lives it. I.e. in response to climate change, if the change is slow enough, a species can select for those with the longer fur or the better sweat glands, etc.
On a parallel note, how often in selective breeding might we expect a genuine mutation to appear and to select for? There seem to be some oddities like Devon Rex. But it would be interesting to understand how often we get a new component in the puzzle rather than just working through the combinations of existing bits.
The case of water buffalo (Bubalus bubalis) may add clarity … or confusion. There are two main breeds, or subspecies, of water buffalo, swamp (48 chromosomes) and riverine (50 chromosomes), which were domesticated independently. Both subspecies are considered to belong to the same Bubalus bubalis species even though they apparently diverged 1.7 million years ago, and even though the subspecies have differing numbers of chromosomes!
I became aware of this because of efforts to develop a river-swamp hybrid. I guess the river breed is better for producing mozarella cheese, but the swamp breed is adapted for Thailand’s heat. IIUC, the first hybrid generation has 49 chromosomes, but the 2nd generation has 48 and is therefore ready to interbreed routinely with swamp buffalo.
I’m surprised the two varieties are considered the same species, despite the differing chromosome counts. Are there many examples like this?
Chromosomal polymorphism, that is, different chromosome counts (or shapes) within species, has been found in many organisms. Whether differing numbers of chromosomes result in sterility depends on whether or not the chromosomes cans still pair correctly during meiosis. For example, sometimes the difference is due to a chromosome splitting or two chromosomes fusing in one population. As long as the chromosomes can still pair up with the original chromosomes the offspring may be fertile.
One example is the Prezwalski’s horse of Asia, the only surviving wild horse. It was thought to be an ancestor of domestic horses but genetic analysis suggests it is a different lineage. Despite having 66 chromosomes to the domestic horse’s 64, they produce fertile hybrids. In contrast, donkeys have 62 chromosomes but produce sterile mules when crossed with domestic horses.