Observing the Origin of a new Species...

[Ganoderma]

here is a fairly decent easy to read description of specie definitions.
Species - Wikipedia, the free encyclopedia

the main problem i have with the reproduction definition is that, by current taxonomic status, many animals/plants break that rule. for example members of the Genus Pogona (a common pet lizard known as bearded dragon) have been quite successfully inter bred (barbata x vitticeps, perhaps rankins as well?). Members of the genera Lampropeltis and Elaphe (milksnakes, kingsnakes, rat snakes etc...) have been interbred a LOT within their own genera. There are hybrids of Python species (P. morellia x P. viridis, P. regius X P.curtus etc...).



Take this even further into cacti. members of DIFFERENT genera can sometimes be crossbred as well. for example there are a relatively large amount (considering how rare the 2 parent species are) of Lophophora sp. X Ariocarpus sp.. That said, cacti taxonomy is anything but good. so maybe they are actually related. there are other examples everywhere of SPECIES cross breeding, even GENERA cross breeding (reptiles just happen to be what i know more about, so they are my reference).

[Pyrotex]

Originally Posted by Ganoderma

...the main problem i have with the reproduction definition is that, by current taxonomic status, many animals/plants break that rule. for example members of the Genus Pogona...have been quite successfully inter bred....

As per earlier posts in this thread, the "problems" with the definition of "species" are quite common.

But look at it this way. IN THE WILD, members of Genus Pogona typically do not breed, make no attempt to breed, and may perhaps not even encounter each other. IN THE WILD. So, they are different species. The mere fact that you as an interferring human can "make" them interbreed may be irrelevant. IN THE WILD, they don't have tall two-legged critters forcing them to mate against their wills.

Take another example: dogs. Assume humans disappear and all dogs find themselves free of restraint and on their own. Focus on Dobermans and Chihuahuas. Now, technically, the two variations CAN interbreed. And I've seen a Chihuahua attempting to hump the leg of a Doberman years ago. (It was quite funny.) But to no avail. [sigh] So, the desire to interbreed may be there.

But, IN THE WILD, would Dobermans and Chihuahua successfully interbreed and successfully produce viable progeny. Not bloody likely. For one, they would be attracted to different prey in different kinds of terrain. Where the Dobies flourished, they would probably run off the Chihuahuas (or include them on their menus).

Given their stark differences in appearance, different prey, different terrains, and the near-zero probability of mating and producing offspring, not to mention the sheer mechanical difficulty of transfering sperm, it would be logical to say they are different species. I don't have a problem with that. But I know a lot of people that would.

[Ganoderma]

i am not so sure they wouldn't interbreed (pogona sp.) in the wild. with most reptile husbandry we do not force breeding, that is actually quite difficult. we mimic weather patterns and they go about doing so on their own. in fact, if you start touching and playing with them, likely they will stop. likewise for other lizards, frogs, snakes etc...

Also lets not confuse physicall divisions as specie borders. ie mountains, water etc. in the wild they are separated (i think this is one reason that leads to new species, they are separated and adapt to new environments). that said if placed together during breeding season they will likely still breed. i see no difference in breeding in the wild or captivity in terms of mate selection (talking about Pogona here). IN a reptiles magazine a few years ago it showed a male Pogona barbata mating a Chinese water dragon (latin name escapes me). they are way different, but both agamas.

another example would be king snakes. these are found throughout the Americas. many f these are commonly cross bred for pets, but they also usually overlap in wild locality. i *think* wild hybridization is more common than we think. the problem is our taxonomy is...lacking... and how can we differentiate a hybrid if the pure specie is hard. i think that a hybrid is likely just called a colour phase when seen.

wild hybrids have been shown, but i think in captivity it shows that it is possible. i dont think it is a good definition "Animals that wont breed in the wild are different species". That just shows that they are mentally different, but physically they can. and right now, taxonomy is strictly based on physical characteristics.

Then enters the sub-specie. They can interbreed. Veering away from animals (cause it’s a little harder for me to decide on) and moving towards cacti again. Different genera have been successfully hybridized many times. Cacti alone throw out the reproduction rule. That or its taxonomy is horrible (which it is). If you look and see how many synonyms there are for various species, it makes you wnder if these scientists are on crack.

Edit: what i am saying i guess is i think genetics are where we need to be focusing. worry about morphology later to help key out species. if 2 aniamls can successfully breed that shows they are at least VERY similar genetically. despite being too small to get in the hole (your dog example).

[Pyrotex]

Originally Posted by Ganoderma

...That or its taxonomy is horrible (which it is). If you look and see how many synonyms there are for various species, it makes you wnder if these scientists are on crack. Edit: what i am saying i guess is i think genetics are where we need to be focusing. worry about morphology later to help key out species. if 2 aniamls can successfully breed that shows they are at least VERY similar genetically. despite being too small to get in the hole (your dog example).

Yes, Taxonomy is inconsistent (with respect to interbreeding)--I wouldn't call it "horrible". The trait or attribute of being able to interbreed as a requisite of being in the same species is a "rule of thumb"--a heuristic--not a Rule or Law.

Look at it this way: from Nature's point of view, there ARE NO SPECIES. There are just animals and environments. Period. There are no chemical, genetic, phylogenetic, behavioral or morphological "boundaries" that Nature sees and recognizes.

[yes, I am anthropomorphizing Nature here, but "try it on" for the sake of argument]

What Taxonomists do is (from Nature's POV) assign arbitrary names and divisions. Not arbitrary from a Human POV, because we attempt to create these divisions according to some "rules" that we think important. But Nature herself does not have or acknowledge those rules.

There are animals. Some animals hang out in herds and some interbreed. Those that do tend to look alike. But there are genera with so many variations that Taxonomists run out of names and attributes and wind up creating (arbitrary) species that CAN interbreed with other species. It's a name game.

But Nature doesn't know a Connochaetes gnou from a Strigiphilus garylarsoni. Nature knows animals, sex, procreation, passing on genetic attributes, building new bodies, shells, leaves, etc.

As a teenager, I watched in fascination as our dog Chipper copulated with our Siamese Cat, Teeny, who offered no protest. Does that mean they were of the same species?

[Ganoderma]

by some standards if your cat gave birth fertile pussydogs then yes

i know what your saying, and fully agree. But with that mentality, why ask to see the origin of a new specie if a specie really doesn't exist? we just wanna know how they evolved and grew and where they are going. placing them in very distinct groups makes it far easier to do so. i would far rather have a key to the animals/plants i am trying to research.

i would rather know "dorcus titanus sitka" rather than that big black beetle with pinchers from taiwan (perhaps over 100 "species").

in a way nature cares nt, but us humans care therefor nature cares. we are beyond, i am hungry lets kill. i have no kids lets make some. some of us are anyway

[Pyrotex]

I appreciate your thoughtful response.

Fortunately, Teeny did NOT have any pussydogs, and so the Taxonomists' jobs and careers are safe for the time being.

Nature has its own agenda. We can find variations of the same species that look totally different. Some of these pairs can interbreed, others can't. We can find variations of the same species that look identical. Some of these pairs can interbreed, others can't.

We have a rule of thumb which says that the more two variations look alike, the more likely they are to be able to interbreed. Exceptions exist.

We have a rule of thumb which says that if two variations do NOT attempt to breed in the wild (though available to each other), the more likely they are to be mutually infertile. Exceptions exist.

We're pretty much stuck with rules of thumb and their exceptions.

So, how do we determine whether or not a new species has emerged. Richard Dawkins addressed this in one of his amazing books, but I forget what he said. Partly. Wait. "A River Out of Eden". Yeah. I remember now.

Think of the DNA of all life as a huge river that is constantly branching and splitting. Each branch of the river represents a unique species. Two strands of DNA (mud buffalo, water buffalo*) come to a fork in the river; one goes down one fork, the other takes the other fork. The two strands of closely related DNA, produced offspring with each other all the time--before the river forked. After the river forked, the two strands never, ever saw each other again. They were now on different genetic and evolutionary branches. One would eventually become the red-breasted, single-humped buffalo, and the other would eventually become the gray-headed, double-horned, jungle yak. Eventually. At that point, they would obviously be of separate species.

Dawkins asks: given two interbreedable DNA strands floating down the river, at what point do you decide they are on separate branches? Note that the river boundaries are "fractal" in nature. As the river spreads out, an island may appear in the middle, and you may think that marks the "beginning" of the split, but wait. DNA can still cross to the other side of the river after the island, and between the islands.

Then more islands appear and the middle of the river gets shallower. But it is still possible, though unlikely, for one DNA to float over the shallows to the other side. Then the islands and shallows begin to merge together in a marsh that separates the river into two branches. But wait! There are rivulets and creeks that criss-cross the marsh at high tide, and it is still possible that a DNA strand floating on one branch of the river might just maybe possibly incredibly manage to float through the marsh maze and rejoin its brother DNA strand on the other branch (meaning that they resume interbreeding).

Further down the two branches, the marsh land firms up into dry land, and one would think that the two strands of DNA are now hopelessly separated so that all interbreeding is impossible. But there are flukes of nature. Perhaps after several miles of dry land between the two branches, they merge again into one river!!! This is a metaphor for the extremely rare event where a proto-species that, through a fluke of genetic accident, can still form a fertile hybrid with a related proto-species, after perhaps millions of years of genetic drift away from each other, and they resume interbreeding.

Dawkins asks the metaphorical question, exactly WHERE did the big river become two branch rivers? (At what point did one species become two species?) And the answer is, there is NO definitive answer to that question. There is NO sudden, quick, decisive "split" (measured as a moment in time) where you can say confidently, no strand of DNA on one side will ever reach the other side. (Interbreedability switches instantly to nonbreedability.) Genetic separation simply doesn't work that way.

All that one can say is that HERE we have TWO branches. They are TWO species. And if we check the historical data (fossils, perhaps) we see that these TWO rivers were once a SINGLE river. Back then. The split occurred somewhere between now and back then.

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* the two imaginary buffaloes are identical, except that one has a slight preference for wallowing in mud when it's available. The other, generally speaking, does not wallow in mud.

[maikeru]

That's a beautiful post, Pyrotex. You should get it framed. I remember when the same realization dawned on me after taking a few biology classes and learning more about DNA and evolution. I think natural languages also show some similarities to the ways species diverge, producing incredible complexity and richness (especially prior to printing, standardization, and nationalization). There are no easy answers.