Definition of "Species"

[saximus]

This is probably one for the biology geeks out there.
I have been reading a fair bit about evolution lately and one thing that comes up a lot (generally in arguments between creationists and evolutionists) is speciation and what defines "species". This has got me thinking a lot about herp genetics. It's my understanding that animals when animals undergo speciation they are said to become different species when they can no longer breed together. However, we have seen people breeding different species of snakes together (examples like the woma ball or whatever it's called and jagpondro come to mind). So basically I guess my question is how do these animals reproduce together if the general definition of species states that they shouldn't be able to?
Also, thinking of other animals, why have dogs not undergone speciation? Surely at least some pure breeds have been separated from the rest of the breeds to allow this to occur?

 

[Snakeluvver2]

From my limited understanding and my brief talks with a few ecologist/natural scientist.
The definition of a species is under-going radical change.
Also it gets more complicated with different animals, so do all creatures get judged the same? That was my question.

 

[longqi]

Very good question and hopefully some interesting debate on this one

 

[Jazzz]

when 2 animals can produce fertile offspring is major factor. like a tiger and a lion produce an infertile liger

 

[Snakeluvver2]

Dog and Dingo?

 

[saximus]

So are woma balls and carpondros infertile?

 

[CamdeJong]

I have the same problem with taxonomy, a while back I was discussing a related topic on here and made my opinion based on the idea that species are defined partially by the fact that they have diverged far enough that their anatomy, behaviour or range to stop them from interbreeding. Then I learned that species like Pogona barbata and vitticeps can breed, and that was only the start of it. Ball x Womas and such things render the Morelia spilota group, and subspecies definition itself, moot when considering it from a breeding perspective. If species from separate Genera or even Families can cross then species shouldn't be defined by that.
In terms of dogs I don't believe normal evolution will ever apply. Natural selection doesn't apply when we decide what environment an animal lives in and its survival depends on us.

 

[Jazzz]

yeah thats why i said it was a major factor... i didnt know any species that it didnt apply to until i learnt about the snake cross breeds. Dogs and dingos can produce fertile offspring although they have only just become separate species. They only separated from dogs a few thousand years ago though so i dont think they have evolved enough separately.

 

[Snakeluvver2]

Cool thanks for the info! Might ask a friend about this!

 

[Jonno from ERD]

The inability to interbreed is not a set diagnostic characteristic when definining what constitutes a valid species.

Taxonomy will never be an exact science. Science is forever trying to formally categorise what are simply points on a continuum. It will always be a matter of contention.

 

[Snakeluvver2]

Ctenotus (Robustus in particular) is a good example.

 

[lace90]

There are different species concepts that taxonomic use when defining species. The Biological Species Concept is the one most if you are discussing with the reproductive factor. There are many others that can be used for species definitions. As long as it is stated what concept was used in the description, which is not always done and therefore it is difficult to dispute the species if changes are found, then things should be clear. As a taxonomy student, I get so frustrated that there is not some uniformity, even just among classes, so that all species within that clad have been described using the same concept. Frustrating! And then you have to question the purpose of turning morphs it localities into subspecies or splitting species when the original concept is still in place??
For the insect species that I am splitting into multiple, i have proof that no hybridising has occurred for many generations WHEN THEY HAVE BEEN EXISTING IN SYMPATRY, look it up its important!, and I can then use the BSC as I said above. But when put together in an artificial environment, there is the possibility that cross breeding can occur. Such a tricky business.

 

[saximus]

Hmm interesting Lace thanks. I was hoping you'd have some input here
Jazz what is the new species that Dingos come under? Wiki still has them as a Canis lupus dingo

 

[Jazzz]

it used to be Canis familiaris dingo, i think it changed early 90s

 

[saximus]

Oh right. So does that mean the dog used to be classified as a different species to the grey wolf (C. lupus) as well?

 

[Jazzz]

yeah it used to be Canis familiarus domesticus. It got changed at the same time as the dingo =]

 

[fugawi]

I think, we, as humans, are compelled to try to put things in boxes and try to have everything nice, neat, tidy and categorised. Sometimes things don't fit into our boxes, so we just make a bigger box and lump them together.

 

[dihsmaj]

So are woma balls and carpondros infertile?

If Woma balls were infertile, how would there be any Woma pythons?

 

[Bluetongue1]

This extract from Wikipedia should answer the last few questions:

“The Australian Dingo or Warrigal is a free-roaming wild dog unique to the continent of Australia, mainly found in the outback. Its original ancestors are thought to have arrived with humans from southeast Asia thousands of years ago, when dogs were still relatively undomesticated and closer to their wild Asian Gray Wolf parent species, Canis lupus. Since then, living largely apart from people and other dogs, together with the demands of Australian ecology, has caused them to develop features and instincts that distinguish them from all other canines. Dingoes have maintained ancient characteristics that unite them, along with other primitive dogs, into a taxon named after them, Canis lupus dingo, and has separated them from the domestic dog, Canis lupus familiaris.”

All dogs are the same species as the wolf. It is only at the sub-species level they are split up.

Blue

 

[saximus]

If Woma balls were infertile, how would there be any Woma pythons?

That makes no sense

Thanks Blue. Helpful as always