A debate with myself and a creationist a long, long time ago got to the point of him mentioning something that got me thinking, how hard would it be to selectively breed a new species? Yes, I’m aware of the different breeds of plants and domesticated animals, but I’m thinking more of an animal that differs so much from the original it CANT be mistaken for anything else. Maybe a different genus.
Would it be possible to take a small, quickly reproducing mammal (say a rodent for example) and selectively breed it into something that doesn’t even come remotely close to a rodent? I imagine it might take a while. Can it be done?
IIRC correctly the main determinant of separate "species" is not looks but that they can’t breed with each other and produce viable issue.
To do enough breeding change ups that the egg and sperm won’t take would (I’m guessing) take many more generations than just the change ups necessary for a different* looking* animal.
Does a chihuahua come even close to resembling a wolf? That should answer that part of your question. But “species” as it’s usually currently defined is based on whether animals interbreed in the wild, and there’s no such thing as a human-bred wild animal, so the very notion of “species” is ill-defined for human-bred animals.
We’ve been selectively breeding dogs, cattle, etc for hundreds of years, and we haven’t produced a new species yet. And techincally, you can’t produce a new species by selective breeding-- not in the BSC (Biological Species Concept) sense of that term. The BSC requres that populations cannot or do not normally interbreed in the wild to be considered distinct species. As was pointed out by one of our resident biologists in a recent thread, the concept of “species” as commonly used by biologists does not apply to domesticated animals, all of which are defined to be the same species as the ancestral popluation.
Probably what you want to ask is if a population can be selectively bred so that it no longer can breed with it’s ancestral population even in a controled setting. I suspect we could easily do that with genetic engineering, but I don’t know how far we could get with old-fashioned selective breeding programs. Animals that could be produced by that method which could not breed with the ancestral population would likely be individual mutants that probably couldn’t breed with anything.
Keep in mind that cross-species and even cross-genus hybrids are very common. These represent populations that have been isolate from each other for millions of years. For example, all species of the genus *Canis * (dogs, ,wolves, coyotes, etc) are inter-fertile.
On the other hand, if someone wanted to, it wouldn’t be very difficult to breed something that wouldn’t be interfertile with the parent species, and then release it into the wild, where it would then fail to interbreed. Especially with plants. It’s just that when we go to the effort of selectively breeding something, we’re not doing it just so we can let it go at the end to prove a point.
Are corn and teosinte interfertile? They don’t much resemble each other at this point, not that corn would be a very viable species if it weren’t cultivated.
On what basis do you come to that conclusion? I don’t see any reason that it would be easy at all to do that. Not by breeding, as opposed to genetic engineering.
Good question, but I don’t know if there is a yes/no answer. Teosinte:
There are really two separate questions here, which are not directly related:
Can scientists produce reproductively isolated populations through selective breeding?
Can scientists produce drastically different-looking populations through selective breeding?
The answers to both questions is yes.
Regarding question 1:
As has been mentioned, technically the Biological Species Concept cannot be applied to artificially selected populations. However, since the BSC requires reproductive isolation between populations to consider them separate species, we can look at whether this criterion has been produced through selective breeding.
Note that it is not necessary for two populations to be intersterile to be considered different species. It is only necessary that they do not regularly interbreed where they come in contact, whether for behavioral, ecological, or physiological reasons.
This page discusses various experiments on fruit flies and other species. (It also has a useful discussion of species concepts.) Within only a few years, selective breeding experiments have resulted in populations with a sufficient degree of reproductive isolation that they would be considered separate species if found in nature.
Regarding question 2:
Many of the different breeds of dogs are different enough from each other, and from the ancestral wolf, that they undoubtedly would have been considered separate genera, not just separate species, were they to be found in nature. Breeds of many other domestic animals, as well as laboratory strains, would easily be considered different species, if not genera, if found in nature.
Now these breeds of dogs are considered to be the same species as each other, and as wolves, because they are interfertile. However, this is just a convention, because all species in the genus Canis, including wolves, coyotes, and jackals, are also interfertile in captivity. By interfertility criteria alone, there would only be one species of Canis. By morphological criteria alone, there would be multiple genera within the domestic dog itself.
And certainly some breeds of dogs, such as chihuahuas and dachshunds, are so different morphologically that they physically would not be able to breed with wolves. By both the interfertility and morphological criteria, they would qualify as separate species from wolves, were they to be found in nature.
One other case that might be mentioned is the llama Lama glama and the alpaca Lama pacos. These domestic forms have traditionally been considered to be separate species, although they are both derived from the wild guanaco Lama guanicoe. While they are morphologically somewhat different, they are all interfertile. Here you have a case where two closely related domestic forms were classified as separate species by taxonomists before their true origin was known.
If my understanding is correct, plants are pretty easy to change from haploid to duploid, etc, and the extra/missing chromosomes render the result completely reproductively incompatible with the originals. I’m not a geneticist or anything and could be wrong about this. If I am, by all means fight my ignorance.
For animals it’s trickier, but with a short-lived critter like the ever-popular Drosophila melanogaster one can get pretty rapid and extensive modifications. If I’m not mistaken, there’ve been some lab strains developed that aren’t interfertile with parent populations.
The thing is, if you released all domestic dogs into nature, they’d all fuck each other silly and in a dozen generations you’d have dramatically dimished morphological differences. Even seemingly improbable matings would occur - I know of a tiny annoying yappy terrier cross that successfully impregnated a Doberman bitch that stood 5x taller than the terrier mutt. While a population of just elkhounds and chihuahuas would probably be behaviourly reproductively isolated in the wild, a population with a few intermediate-sized breeds would be one continuous mess of gene flow.
Not that I really disagree with anything you’ve said, but without the artificial reproductive isolation imposed on dog breeds by breeders, breeds would rapidly cease to exist.
True, but that’s not the question. It is impossible to be sure what would happen in nature based on what happens in captivity, which is exactly why the BSC can’t be applied to artificially selected populations. My point is that the different breeds of dogs are analogous to morphologically and reproductively distinct species.
I would suggest, however, if one were to introduce just chihuahuas and elkhounds onto an island where both were capable of surviving, and where no other canids were present, and if there were distinct ecological niches available for the two different size classes, it is likely that they would persist and function as two separate and very distinct species. Of course, this is not a very realistic scenario.
If we released a population of chihuahuas (or any dog small enough that it physically couldn’t breed with a wolf) into an area where wolves occur, they’d most likely end up as a wolf’s lunch, if they could even survive on their own for a few generations.
I know you’re joking, but just to continue with the point of my last post, that’s because chihuahuas aren’t going to be very capable in the wild in general. But small canids, such as foxes, survive just fine within the range of wolves.
The problem is, if one produces a new “species” by artificial selection, it almost of necessity is going to be less fit in the wild than one produced by natural selection.
Yeah, because those small canids evolved within the range of wolves.
But let’s take this one step further. Suppose that some small domestic dog was capable of surviving at least long enough that a pack of such dogs came upon a lone female wolf-- one seperated or rejected from its own pack. Would the wolf view that pack of domestic dogs as group that it would want to integrate itself into? And if so, is it conceivable that it would allow one of the male dogs to mate with it?
John, you may be missing my point somewhat. The question is irrelevant with respect to the OP. The question is not, I think, whether artificial selection has, or is capable of producing, organisms that can survive and maintain their genetic integrity in the wild, but whether artificial selection can produce (artificial) entities that are conceptually equivalent to real species. Some domestic dog breeds fit the criteria both on morphological grounds, and on the basis of intersterility due to physical incompatabilty.
This said, even in your example, it doesn’t really matter what happens in that particular case, as long as a female wolf prefers to associate with and breed with other wolves if given the opportunity. Occasional interbreeding regularly occurs between “good” species in the wild, especially where one of two closely related species is rare and doesn’t have the option with mating with its own kind. As long as the small wild dogs and wolves normally associated with and bred with their own kind, they would be good species as long as hybridization was infrequent.
Colibri: I do understand that, so let me explain what I’m trying to get at. Wolves presumably have some mechanism for recognizing potential mates or at least recognizing potential social partners. As I understand it, this process happens when a lone male and female pair up, or when a lone wolf tries to integrate into an existing pack. So, what is it that attracks two lone wolves to each other, or compells one lone wolf to join an existing pack? Is it behavioral cues or some “smell” the animals have, or something else, or some combination of those things? So, would a lone wolf, seeking to find another wolf of the opposite sex recognize a domestic dog as one of its own, or would it view it as it might view a coyote or a fox-- something close, but not quite what its looking for.
I’ve definitely seen how dogs (regardless of their breeds) react completely differently to other dogs (reglardless of their breed) than they do to other species. So, would a wolf see a dog as another wolf, or as some foreign species? Would a dog “smell” like a wolf to another wolf? Different breeds of domestic dogs will form packs if they’re left in the wild, so how do they know if some other dog is a poodle, a german shepherd, or a wolf? And if domestic dogs can’t tell the difference, how would wolves tell the difference?
I’m also assmuning (and maybe this is wrong) that domestic dogs would be behaviorally compelled to form packs in the wild as opposed to living on their own (as coyotes usually do).
Dogs may well recognize each other as the same “species” by smell, and might not differentiate a wolf either. Feral dogs run in packs, like wolves. A wolf pack might well accommodate a feral dog that could keep up with it (though I don’t know of particular examples outside of Jack London stories). If you put feral dogs of appropriate size and wolves together in the wild, if the dogs weren’t killed in short order there might well be an amalgamation of the populations.
But what I am postulating here is a sufficient size difference so that this pack of feral chihuahuas is incapable of mating with wolves, or at least that such matings will generally be rare and/or unsuccessful. The size difference will also force the chihuahuas into a different ecological niche - a chihuahua wouldn’t be able to keep up with a wolf pack, nor could a wolf hunt with a chihuahua pack. Under such conditions the two forms will function as separate species, even if they recognize each other as the same and are technically interfertile.
Once again, let me reiterate that this is not a realistic scenario, since real chihuahuas couldn’t survive in the wild, and is in any case not directly relevant to the OP.
I guess my mind was too fixated on sex to think it all the way thru and realize that they’d have to live and hunt together afterwards. Even dogs can’t live on love alone!
Of course. It sure would be interesting to see a pack of hunting chihuauhuas, though!
I’m afraid I was a bit unclear on the OP. I’m not saying to selectively breed an animal simply looking different, I’m saying to breed an animal so taxonomicaly and genetically different that the criteria for genus isnt there anymore.
But the chihuahuas are still dogs though, other dogs recognize them as such, and they are still technically capable of reproducing with other dogs. The differences I’m thinking of are more like breeding a dog with the morphological and genetic differences of say, a cat.
The most recent common ancestor of dogs and cats lived something like 50 million years ago. With selective breeding we can accelerate genetic changes in a population to a degree, but only within limits. How much time are you willing to give your hypothetical selective breeder?
