Definition of Species

I hate species, it has so much baggage and people have such miconceptions about what a species is. I wish we could forgoe the concept of species altogether and just talk about reproductive isolation. Sadly the whole species concept is such a handy and entrenched way of talking about evolution and systematics and the relationships between divergent populations.

Heh. But then cladistics wouldn't be nearly as much fun... Actually, I don't have a problem with species, or any of the other words we use for classifying organisms. It's a pretty convenient way of organizing bunches of organisms in terms of relatedness. It might be nice if there was some way of making the determination of whether a given group was a species or two species or..., a tad more rigorous, but as long as everyone recognizes that it's simply a label - an abstraction, if you will - there really isn't any major problem. It's only when people try and assign some intrinsic "reality" to the term that it falls apart. Besides, how would paleontologists determine reproductive isolation when classifying extinct organisms?

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It seems to me that if we took the full range of existing dog breeds and "extincted" all of them except for Great Danes and Chihuahuas we'd have to distinct species left.

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I'm glad you said this. I didn't want to sound stupid, but it seemed really odd to me that every definition of species would leave St. Bernard and Chihuahua in the same species. They clearly would not breed, and probably could not produce any viable offspring unless you helped them in the laboratory.

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And that's one of the difficulties we face today in determining "species--" IVF. Certianly taking the sperm from a St. Bernard and a chihuahua egg could produce a fertile offspring (though I doubt the chihuahua could carry it!). However, if we only had fossilized chi's and St. Bernard's and knew nothing about their reproductive compatibility, it's likely they'd be considered different species. Similarly with species who may produce fertile offspring but are geographically isolated and may have different mating rituals. They'd never mate in the wild, but their gametes are perfectly compatible in the lab. Are they different species or not?

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How much time would it take for the Chihuahua to be so much like a rat that we'd classify it as a rodent? Well, in nature, it would probably never happen, because Chihuahuas are a mess physically, and they'd just go extinct.

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Hey, I love my chihuahuas! I'm assuming the rodent part is in jest--though they may look like big rats, their physiology is quite different, so they'd never be classified as a rodent.

I talked to a dog breeder friend. She has French bulldogs. Apparently these things are so specifically bred they can't successfully mate with themselves! They need "help" ( I didn't ask for the details ).So I guess these things are an odd dead end of the "evolutionary" branch. I suppose the truth of my little thought experiment is that a number of the more extreme breeds would be gone in very short order.

For what it is worth, Winge, in his book "Inheritance in Dogs" describes a spontaneous cross between a male St Bernard and a female Dachshund. She delivered a normal litter one of which herself delivered young, hereby conforming to Dobzhansky's criterion that they were the same species. It would be interesting to try more reciprocal crosses between large and small breeds of dogs, even if they have to be done artificially. I would be surprised if they failed. They succeed with horses. Dogs are an excellent demonstration of the failure of intensive selection to result in speciation. I have discussed the problem in the Manifesto. salty

You seem to have missed the entire point of the last dozen or so posts on the thread Salty. Your example of a St Bernard Dachsund natural mating merely shows that we might be wrong in assuming that the dogs are even morphologically reproductively isolated. It isnt as if dogs have been intensively selectively bred with the intent of creating new species, perhaps they should be but that might be a very long term experiment considering the generation time of a dog. The only problem is that selecting for morphology is a lot simpler than selecting for reproductive isolation, unless you simply want morhological repoductive isolation which still doesnt affect the genetic compatibility of the dogs.

Thanks for straightening me out. I see nothing has changed. salty

Perhaps the same old problems wouldnt reoccur if you just stuck to the topics and didnt keep trying to steer threads towards your manifesto.What are your feelings on the definition of species? Is it just reproductive isolation that is the important factor in defining species?

I accept Dobzhansky's definition of species because there is nothing vague about it. Furthermore it is testable. Of course I refer to the Manifesto. In it the Darwinian myth has once more been exposed, not by me, but by Broom, Berg, Grasse etc.etc. I cannot believe that anyone can continue to accept the sexual model for macroevolution. salty

May I inquire as to why the hell you're derailing yet another thread with your inane maunderings and utterly unsupported assertions?

Hi Salty,If you'd like to enter Dobzhansky's definition of species into the debate please describe it here as required by rule 4 of the Forum Guidelines: Also, please stay on topic, as required by rule 1: You should address the off-topic subjects you refer to in the appropriate threads.Continued failure to follow the forum guidelines will result in the contents of any of your future messages to this thread being deleted.------------------
--EvC Forum Administrator

Im assuming Salty means this definition"a species is a group of interbreeding populations that are genetically isolated from other groups by reproductive isolating mechanisms such as hybrid sterility or mate acceptability"From his book "Genetics and the origin of species" published in 1937.So in fact his answer to my question of whether species was just a matter of reproductive isolation should have been "Yes".

[Contents of off-topic message deleted. --Admin][This message has been edited by Admin, 05-30-2003]

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Hey, I love my chihuahuas! I'm assuming the rodent part is in jest--though they may look like big rats, their physiology is quite different, so they'd never be classified as a rodent.

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I detest chihuahuas so much I forgot other people might think they're great. Sorry.And, yes, I was joking about the rodent thing.

What are the attitudes of creationists towards the concept of reproductive isolation as a fudamental criterion for definition of a species, how does this clash or dovetail with concepts of Kind?