what does something need to be a "New" Species?

although I study Evolution and things I still never learned what Makes a Species a Species. I need you guys to Help me out please.
Ok Dogs come in Many different kinds of Mutations. and all look extremely different. and Different "breeds" act different. what Makes them all the Same species? and Have we not just seen Random Mutations with Dogs? is this not form of Evolution? sorry if its a Stupid question but its been bothering me. I never covered it before in any Classes. or books I have read

Did I ever mention that's a nice avatar? What was the question again?------------------
En la tierra de ciegos, el tuerto es el Rey.

simply Put why is a Chihuahua and a German Shepherd the same Species?

Okay, I'll jump on board with MrHambre...There is more than one definition of species, it all depends... What a pretty, pulsating design!Anyway, it all depends on, on, on the... Such pretty colors!And the other dependencies that you have to maintain while considering all the dependencies of the species that the species have... Spinning, spinning!And so it is clear of the species that the different differences of the species can have definitions... Command me, oh master!--Percy

so there is no answer? can you guys get serious here[This message has been edited by DC85, 08-12-2003]

my preciousssss.......------------------
Asgara "An unexamined life is not worth living" Socrates via Plato

if there is no reason for it than can someone just say so? is this not Evolution? same with Plants so many Mutations but they never call any of them a new species. why? please answer this[This message has been edited by DC85, 08-12-2003]

See, there's a couple different definitions of species.For animals that are alive right now, the general definition of a species is that all animals that can mate with each other and produce fertile offspring are in the same species. So, since you can fertilize a german shepard with chiuhauha sperm, they're the same species.When you're talking about fossils, you obviously can't tell what a fossil organism can mate with because it's pretty dead. In that case they usually go by the physical features of the organism. But there's always a question - is this fossil a member of a different species? Or is it a member of one species, among which the individuals exhibit great variation (ala dogs?)Basically the conceit is this: if we were looking at fossil german shepards and fossil chiuhauhas, we'd probably conclude they were different species, especially if we didn't have fossils of the various intermediate breeds between them.

can't Wolves and coyotes breed with Dogs also? but yet they are different I don't think they are sterile either(not sure)[This message has been edited by DC85, 08-12-2003]

Well, you've hit on one of the problems with using genetic incompatability as the only criterion for species identification.Biologists generally say that if two populations of animals don't mate with each other in the wild, inhabit different biomes, other exhibit other kinds of separation, they're two different species. But it's not an exact science, really. As evidenced by the continuous debate that occurs in the biology journals about precisely what species a given individual represents.There's all kinds of reasons why two individuals won't mate with each other (this is called "reproductive isolation" and it's the cause of speciation). One is that they're not in the same place (geographic isolation). Another is that for reasons of behavior they don't see each other as mates. Another is that for reasons of physical shape they can't fit the naughty bits together. Yet another is that a hybrid fetus can't survive in the mother's womb. Another is genetic isolation - their sperm won't fertilize the other's egg.This is kind of tangental to your question but you have to define "species" based on what leads to new species, generally.And lastly, I'm not a biologist so this could very well represent a very poorly informed opinion on the matter. I won't argue if anyone has corrections or clarifications.

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can't Wolves and coyotes breed with Dogs also? but yet they are different I don't think they are sterile either(not sure)

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I believe one of the first conversations I had after joining , was this very matter.As I recall, the wolf is Canus lupus.I have seen the domestic dog listed as a separate species, Canus familiarious (sp?), and as a wolf subspecies, Canus lupus familiarious.I personally like the subspecies (aka "breed"?) designation. As far as I know, wolves and domestic dogs are not at all reproducivly isolated. Wolf/dog hybreds are fertile, and can further reproduce.I may be wrong,
Moose

The problem with using dog breeds as an example is that dogs are a man-made phenomenon. I doubt there are any species in the wild that exhibit the range of phenotypic variation that we have created in dogs.The definition of species as being reproductively isolated is a useful one for most purposes, but in reality there are grey areas. Which I'm sure creationists don't want to know about, because it puts a hole in their idea that species are clearly defined and can't change (eg. into new species).------------------
o--greyline--o

Species will always remain a difficult concept and hard to define because it is an attempt to make a divide up a process into discreet units. It will also not be equivalent among phyla for example how you define a bacterial species will not apply to how you define a mammalian species...I have never been entirely comfortable with the concept that reproductive isolation should be the utlimate definition. F1 hybrids of lots of groups can be produced..even among genera i.e. there was one successful cross of an African elephant (Loxodonta africana) with an Asian elephant (Elephas maximus). However the hybrid died after 10 days. Lots of F1 males are sterile in mouse crosses. So the fitness of the F1s is highly reduced but they are not technically reproductively isolated. If two species of monkeys produce offspring that are viable and fertile but the offspring are too stupid to feed themselves are the parents different species? I would say yes because ultimately the F1's, F2's etc. will never be able to transmit their traits very far into the future i.e. low fitness relative to the parental types.The danger is that one can take this to extremes like those who are strict proponents of the phylogenetic species concept...I have run into a few who would say a single base difference in a cytochrome b sequence defines a new species...great..then every organism on the planet is a species except for clones...how useful is that for a definition?The dog breed examples are not bad, but it adds a complicating factor i.e. that natural selection is not at work. Many dog breeds would never make it in the wild i.e. chihuahua's, bulldogs, etc. These breeds are only maintained by a lot of intereference from humans to maintain the breeds against the tendency to vary...what is the significance of fitness then in a species where the highly non adapted traits are kept at high frequency by people selecting for aesthetics rather than survival ability or fecundity?My rather long winded 2 cents

I think that in evolutionary terms at least the inability to produce fertile offspring is a reasonable definition. Where this does become more problematic is in the cases which have been brought up several times of ring species and dogs. I'm not sure that crash is right in putting so much emphasis on the genetic incompatibility rather than simply reproductive isolation. I understand that there are a number of problems with simply considering reproductive isolation, does a population which gets completely cut off geographically suddenly become a new species just because of its location, of course not but two populations which develop different mating rituals may be completely interfertile but never mate naturally, why should they not be considered a species, surely the situation as it pertains in nature is the important one, not what we can get away with in a lab with a bit of fiddling.I don't think that reproductive isolation through pre-mating and mating as opposed to post-mating can be dismissed as a species criterion.

I still think it has to be looked at family by family. Hybrid zones of crickets and baboons are known where F1's are produced all the time. The F1's cannot reproduce themselves but they are continuously replenished by the parental species that live in proximity to one another...are the parentls the same species since they produce offspring even if the offspring have fitness zero?I am not dismissing pre-mating and mating isolation as criteria for a species definition. I just think that fitness of the offspring generated should be taken into consideration and that one will seldom find a clear cut or discreet separation of species...it gets more complicated with cichlid research and incipient speciation. Again, it is very difficult to define discrete species when populations genetics and speciation are both a process and not discrete.