Difference between breed and species?

[PlaidJaguar]

This has been bugging me for awhile. A species is typically defined as a population of animals that can interbreed and produce healthy offspring. Yet the threads concerning hybridization suggest to me that tarantula species can interbreed.

Can anyone explain this for me? Why are the different T's considered species and not breeds? Would it be possible to create a tarantula breed if one set out to do so? (Please note that I'm not advocating this! Just a question of pure scientific curiosity)

 

[JZC]

Tarantulas are different species because a g.roses is not a g.pulchripes, and mixing those would make a hybrid of species. All dogs are canis lupus familiaris and therefore can be mixed because that is producing traits, a variation on the same species. A great Dane and a yorkie are the same species. You can breed them and make more dogs in which each parent passes on traits, but breeding different species is like breeding a human and a monkey. It doesn't work (or it gives you HIV)

 

[Kaltheory]

but breeding different species is like breeding a human and a monkey. It doesn't work (or it gives you HIV)

Yeah! Thanks a lot, monkeys.

 

[PlaidJaguar]

But, aside from the fact that someone told us they're different species, how do we know? Aphonopelma calcodes looks a lot like Aphonopelma sp. "New River " or "Payson Blonde." Why isn't it possible that these are breeds within a species? What's the criteria?
If you breed them, aren't the offspring fertile?

 

[JZC]

Classification is based on DNA and minute traits. They are different because they don't share the same genome and traits. Again, like us and monkeys.

 

[Poec54]

They are different because they don't share the same genome and traits. Again, like us and monkeys.

Although the difference between monkeys and some individual humans can be a fine line.

 

[PlaidJaguar]

Although the difference between monkeys and some individual humans can be a fine line.

Lol!

I don't mean to be a pain the you-know-what, but are they really using DNA to classify each individual species of tarantula? In TTKG Stan describes the naming process, and it doesn't sound nearly so high tech. He mentions that most are identified simply by description, and the scientific community decides if said description is specific enough and different enough to qualify as a new species.

But none of that answers the question of why each different spider is considered a species and not a breed. Breeds have evolved in dogs, horses, cattle, and cats; why can't there be tarantula breeds?

 

[Formerphobe]

Lol!

I don't mean to be a pain the you-know-what, but are they really using DNA to classify each individual species of tarantula? In TTKG Stan describes the naming process, and it doesn't sound nearly so high tech. He mentions that most are identified simply by description, and the scientific community decides if said description is specific enough and different enough to qualify as a new species.

But none of that answers the question of why each different spider is considered a species and not a breed. Breeds have evolved in dogs, horses, cattle, and cats; why can't there be tarantula breeds?

Yes, they are using DNA to classify many of the species.

Easiest way I know to explain it is:
Tarantula species are to tarantula species as dogs are to wolves, or as dogs are to coyotes, or as domestic cattle are to bison.
Some separate tarantula species (usually within a genus) have been interbred to create hybrids.
Similarly, there are dog/wolf, dog/coyote, and cow/bison (beefalo) hybrids.

 

[JZC]

A breed is a variation on one species, generally bred to enhance a particular desired trait. So theoretically, through selective breeding of say a.versicolor, you can breeds for traits such as size and color. Maybe even temperament. Wince some Ts display color morphs maybe breeding can be done akin to the ball python morphing. Maybe it is possible to create a breed of versicolors with two abdomens that makes a great lap animal. It is all speculation.

 

[lancej]

Lol!

I don't mean to be a pain the you-know-what, but are they really using DNA to classify each individual species of tarantula? In TTKG Stan describes the naming process, and it doesn't sound nearly so high tech. He mentions that most are identified simply by description, and the scientific community decides if said description is specific enough and different enough to qualify as a new species.

But none of that answers the question of why each different spider is considered a species and not a breed. Breeds have evolved in dogs, horses, cattle, and cats; why can't there be tarantula breeds?

The answer is yes, different breeds could be developed in tarantulas. It would involve selective breeding over many generations of the same species. This would involve raising slings to maturity and selecting the ones with the desirable traits you are looking for and breeding them together, then raising those slings to maturity and selecting the ones with the traits you are looking for. You would have to do this until the traits bred true with all the offspring. It would take 2-5 times (maybe even longer) as long as it took to develop different breeds of dogs. Remember that breeds are variations of a single species and not a hybrid of two different species. Time and effort involved is the limiting factor here. Not many people have the time, patience, and desire to undertake such a feat, not to mention that it would be your great, great grandchildren that might get to see the results.

 

[captmarga]

As an equine genetics researcher, the answer is even simpler than this. Species - Horse. Species - Donkey. Species - Zebra. Breed: Arabian horse. Breed: Clydesdale horse. Breed: Poitou donkey. Why are these a breed? They are a population of animals selected for certain trait that breed true AND ARE TRACED by pedigree and bloodlines. In creating a new breed, animals that meet the basic criteria (Height, coloration, long hair on the legs, all-black coloration, all spotted coloration, etc) may be grandfathered in. After a certain number and point are reached, the breed books are closed, and only animals with both parents recorded in the breed books are allowed to be called Arabians, Clydesdales, Friesians, Poitous, Catalonians, Andalusians, etc. Parents unknown? Not an Arabian, no matter how pure it looks.

Bottom line - breeds need traceable, known parent lines. Unless you are willing to keep pedigree records on tarantulas, I don't see it happening. Zoo animals have pedigrees, but they are still just Species, and not breed.

Marga

 

[lancej]

As an equine genetics researcher, the answer is even simpler than this. Species - Horse. Species - Donkey. Species - Zebra. Breed: Arabian horse. Breed: Clydesdale horse. Breed: Poitou donkey. Why are these a breed? They are a population of animals selected for certain trait that breed true AND ARE TRACED by pedigree and bloodlines. In creating a new breed, animals that meet the basic criteria (Height, coloration, long hair on the legs, all-black coloration, all spotted coloration, etc) may be grandfathered in. After a certain number and point are reached, the breed books are closed, and only animals with both parents recorded in the breed books are allowed to be called Arabians, Clydesdales, Friesians, Poitous, Catalonians, Andalusians, etc. Parents unknown? Not an Arabian, no matter how pure it looks.

Bottom line - breeds need traceable, known parent lines. Unless you are willing to keep pedigree records on tarantulas, I don't see it happening. Zoo animals have pedigrees, but they are still just Species, and not breed.

Marga

Thanks Marga! I forgot about the pedigree records. No pedigree = no breed, just species. I don't even want to imagine the paperwork involved in doing something like this!

 

[PlaidJaguar]

Thanks guys! That really clears it up for me.

 

[Stan Schultz]

This has been bugging me for awhile. A species is typically defined as a population of animals that can interbreed and produce healthy offspring. Yet the threads concerning hybridization suggest to me that tarantula species can interbreed.

Can anyone explain this for me? Why are the different T's considered species and not breeds? Would it be possible to create a tarantula breed if one set out to do so? (Please note that I'm not advocating this! Just a question of pure scientific curiosity)

Forgive me for resurrecting a thread that was threatened with dormancy if not death. I'm having a small problem keeping abreast of current events on these forums.

My, you sure know how to ask the tough ones, don't you! :biggrin:

Regarding your question, I am going to throw in a third term, "variety," to complete your triad of confusion. Then, I'm going to ask you to visit the following webpages and read as much as you can without suffering brain damage.

Wikipedia: Species
Wikipedia: Species Problem
Wikipedia: Breed
Wikipedia: Variety (Botany) (Read especially the section "Other nomenclature uses.")

Then, if you have time, go to your friendly, neighborhood, public library, or a local college or university library and see if they have or can get a copy of the Scientific American for June 2008 (Vol. 298, Num. 6). You're specifically interested in Carl Zimmer's article, "What is a Species?" If you're willing to pay for a digital reprint go here.

We can dispatch "breed" fairly quickly. The definition leaves no doubt, a breed is a specific lineage of DOMESTIC animal. It requires human intervention and selective breeding. Wild animals don't occur in breeds. Period.

But, when we consider wild creatures we immediately get into deep trouble. As explained in the SciAm article, at least 26 attempts to define a species have been proposed. And, all have serious shortcomings. The bare faced facts are that there is no all-inclusive definition. In fact, the concept has changed radically since the days of Linnaeus and his Systemae Naturae..., 10th edition, revised. (That was the scientific work that started the science of modern taxonomy.) Every expert has a slightly different "spin" of the concept. And, every time a "species" is described and named, the description at least begins with the tacit phrase, "It is my opinion that..."

In his book On the Origin of Species..., Charles Darwin discusses the relationship of "varieties" to "species," but is very careful to skirt the basic issue that no good definition exists for "species." (Darwin was NOT stupid. He fully realized that he needed the taxonomists' support if his book was to be accepted by science, and he was very careful not to offend that potent group!)

If one stands back and looks at the whole topic of taxonomy with only the single bias that something is obviously wrong with the science because of the number of problems it has, we can make a few very general statements about the relationship of different kinds of animals (1) in the world.

It seems that the different kinds of animals that we know about, both extant and extinct, seem to be organized into "familial" lines. (2) What I mean is that a group of interbreeding animals tends to carry on, generation after generation after generation. However, because of changing conditions these familial lines (some have erroneously called these "gene pools") often drift into organisms that look very much like each other, but that have some significant (3) differences.

As time progresses these variant populations ("varieties" in the Darwinian sense) may accumulate enough different characteristics that are strongly enough evident in some way or ways to prompt a taxonomist to write another scientific paper that starts with, "It is my opinion that..." and thus another species has been identified, described and named.

Worse yet, it is not uncommon for these variant populations to interbreed at their common margins, or even recombine. (Hence our creation and use of the term "hybrid." (4) ) This produces an extremely complex lineage of divergences and anastomoses.

But, what has really been done when this happens? Without mincing words (and this ALWAYS gets me in trouble! ) our taxonomist has found an animal that he thinks he can characterize and fit into an imaginary pigeon hole in a hypothetical "family tree" that illustrates some concept of how all animals on Earth are related. But this intellectual creation, this bookkeeping artifact, only distantly resembles the true nature of the family tree. It doesn't show all the interrelationships, and it shows nowhere near the real number of generations, divergences and recombinations necessary to produce the organism in the bottle of alcohol or formaldehyde sitting on the corner of their desk.

So our taxonomist friend has now become a glorified file clerk, trying to squeeze an unbelievably huge (5), chaotic, analogue system into a vastly oversimplified, artificial, intellectual, digital construct. Is there any surprise that there are problems? The only real question at this point is, "Why hasn't anyone realized this yet (besides me of course), and started working toward a solution to the problem?" Everybody seems to be ignoring the elephant in the room! (See? I told you I was going to get into huge trouble! :fury: )

Now where does that leave us? We need to accept the premise that we're working with a flawed model, and not take scientific names or taxonomic relationships too seriously. When we hear others spouting scientific names we should merely smile knowingly, and get on with our lives. Taxonomy isn't worth flame wars and fractured friendships.

Repeat after me, "We're all buddies here. We're all buddies here. We're all...," and get on with enjoying your little (or HUGE), 8-legged enigmas.

And, be ever ready to change the labels on your cages!

_______________________________________________________________________

"The magnitude of our ignorance [about tarantulas] is staggering."
- S. A. Schultz, TKG3
_______________________________________________________________________

FOOTNOTES

(1) Here I restrict our discussion to animals alone in order to avoid some massive complications.

(2) Note that this is not the same term or concept as the term "Family" as used by taxonomists to label a specific level in their hierarchy.

(3) And even here, the determination of what may be considered "significant" is predicated by at least a tacit, "It is my opinion that..."

(4) But how can one have a hybrid between two species if one cannot truthfully define what a species is? Except with some statement beginning with, "It is my opinion that..."

(5) The last I heard, the total number of different kinds of living organisms on planet Earth (not necessarily restricted to only animals) might number between 5 million and 100 million. It seems that every time we look at new habitats or ecosystems, we find another Ark load of living organisms! And, the total number of extinct organisms might equal ten times that!

 

[lancej]

Forgive me for resurrecting a thread that was threatened with dormancy if not death. I'm having a small problem keeping abreast of current events on these forums.

My, you sure know how to ask the tough ones, don't you! :biggrin:

Regarding your question, I am going to throw in a third term, "variety," to complete your triad of confusion. Then, I'm going to ask you to visit the following webpages and read as much as you can without suffering brain damage.

Wikipedia: Species
Wikipedia: Species Problem
Wikipedia: Breed
Wikipedia: Variety (Botany) (Read especially the section "Other nomenclature uses.")

Then, if you have time, go to your friendly, neighborhood, public library, or a local college or university library and see if they have or can get a copy of the Scientific American for June 2008 (Vol. 298, Num. 6). You're specifically interested in Carl Zimmer's article, "What is a Species?" If you're willing to pay for a digital reprint go here.

We can dispatch "breed" fairly quickly. The definition leaves no doubt, a breed is a specific lineage of DOMESTIC animal. It requires human intervention and selective breeding. Wild animals don't occur in breeds. Period.

But, when we consider wild creatures we immediately get into deep trouble. As explained in the SciAm article, at least 26 attempts to define a species have been proposed. And, all have serious shortcomings. The bare faced facts are that there is no all-inclusive definition. In fact, the concept has changed radically since the days of Linnaeus and his Systemae Naturae..., 10th edition, revised. (That was the scientific work that started the science of modern taxonomy.) Every expert has a slightly different "spin" of the concept. And, every time a "species" is described and named, the description at least begins with the tacit phrase, "It is my opinion that..."

In his book On the Origin of Species..., Charles Darwin discusses the relationship of "varieties" to "species," but is very careful to skirt the basic issue that no good definition exists for "species." (Darwin was NOT stupid. He fully realized that he needed the taxonomists' support if his book was to be accepted by science, and he was very careful not to offend that potent group!)

If one stands back and looks at the whole topic of taxonomy with only the single bias that something is obviously wrong with the science because of the number of problems it has, we can make a few very general statements about the relationship of different kinds of animals (1) in the world.

It seems that the different kinds of animals that we know about, both extant and extinct, seem to be organized into "familial" lines. (2) What I mean is that a group of interbreeding animals tends to carry on, generation after generation after generation. However, because of changing conditions these familial lines (some have erroneously called these "gene pools") often drift into organisms that look very much like each other, but that have some significant (3) differences.

As time progresses these variant populations ("varieties" in the Darwinian sense) may accumulate enough different characteristics that are strongly enough evident in some way or ways to prompt a taxonomist to write another scientific paper that starts with, "It is my opinion that..." and thus another species has been identified, described and named.

Worse yet, it is not uncommon for these variant populations to interbreed at their common margins, or even recombine. (Hence our creation and use of the term "hybrid." (4) ) This produces an extremely complex lineage of divergences and anastomoses.

But, what has really been done when this happens? Without mincing words (and this ALWAYS gets me in trouble! ) our taxonomist has found an animal that he thinks he can characterize and fit into an imaginary pigeon hole in a hypothetical "family tree" that illustrates some concept of how all animals on Earth are related. But this intellectual creation, this bookkeeping artifact, only distantly resembles the true nature of the family tree. It doesn't show all the interrelationships, and it shows nowhere near the real number of generations, divergences and recombinations necessary to produce the organism in the bottle of alcohol or formaldehyde sitting on the corner of their desk.

So our taxonomist friend has now become a glorified file clerk, trying to squeeze an unbelievably huge (5), chaotic, analogue system into a vastly oversimplified, artificial, intellectual, digital construct. Is there any surprise that there are problems? The only real question at this point is, "Why hasn't anyone realized this yet (besides me of course), and started working toward a solution to the problem?" Everybody seems to be ignoring the elephant in the room! (See? I told you I was going to get into huge trouble! :fury: )

Now where does that leave us? We need to accept the premise that we're working with a flawed model, and not take scientific names or taxonomic relationships too seriously. When we hear others spouting scientific names we should merely smile knowingly, and get on with our lives. Taxonomy isn't worth flame wars and fractured friendships.

Repeat after me, "We're all buddies here. We're all buddies here. We're all...," and get on with enjoying your little (or HUGE), 8-legged enigmas.

And, be ever ready to change the labels on your cages!

_______________________________________________________________________

"The magnitude of our ignorance [about tarantulas] is staggering."
- S. A. Schultz, TKG3
_______________________________________________________________________

FOOTNOTES

(1) Here I restrict our discussion to animals alone in order to avoid some massive complications.

(2) Note that this is not the same term or concept as the term "Family" as used by taxonomists to label a specific level in their hierarchy.

(3) And even here, the determination of what may be considered "significant" is predicated by at least a tacit, "It is my opinion that..."

(4) But how can one have a hybrid between two species if one cannot truthfully define what a species is? Except with some statement beginning with, "It is my opinion that..."

(5) The last I heard, the total number of different kinds of living organisms on planet Earth (not necessarily restricted to only animals) might number between 5 million and 100 million. It seems that every time we look at new habitats or ecosystems, we find another Ark load of living organisms! And, the total number of extinct organisms might equal ten times that!

I think you did a wonderful job summing this up! It's almost to the point where common names are more stable than scientific names (just kidding!)! Maybe someday, some brave soul will take on the elephant in the room.

 

[PlaidJaguar]

Thank you Pikaia! I would say that clears things up for me, but technically it really made the whole subject even messier. But that's the fun of science! There's a problem, so you sink your teeth in and try to untangle the roots of it.

Looks like I have lots of reading to do. I will definitely check out those resources you recommended. Luckily I'm a spoiled wife with lots of free time. :grin:

 

[pitbulllady]

A breed is something totally man-made, an specific group of animals within a species that have been selectively bred by humans for specific physical and behavioral traits, with a known and documented family tree, or pedigree. Breeds have "fixed type", which means that they exhibit a very specific range of phenotypical characteristics, and ALL members of a given breed are related to one another to some extent. ALL breeds of animals are domesticated, since it is through the selection for that physical/behavioral type by humans that they exist in the first place, and those traits are what distinguishes them from their wild prototypes. Within the domestic dog, for instance, there are more than 400 recognized pure breeds, each with its own unique traits, both physical and behavioral, and to hopefully ensure that the breed maintains those qualities, each breed has a registry or stud book in which all verifiable members are recorded, and a standard, a written description of the ideal specimen, how it should look and act, which is to serve as a sort of "blue print" for breeders when selecting the parents for the next generation. The whole term of a BREED is based on the concept of eugenics, the manipulations of genetic traits of an organism by humans to serve OUR needs and meet OUR qualifications.

A species, in contrast, is a naturally-occurring group of organisms which share the same evolution, genetic and physical traits, which have virtually identical DNA, which are able to produce fertile offspring that resemble the previous generation. The characteristics, both physical and behavioral, that are found within a species are the results of natural selection, to enable that species to survive in its ecological niche, rather than the results of controlled or manipulated breeding by humans. Within a species, there are often sub-species, which exhibit some variation, enough to make them different, but not so much as to significantly alter their DNA so as to warrant totally separate species classification. Thus, domestic dogs, with all their 400+ breeds and countless mixed-breeds, are still classified as Canis lupus familiaris, a sub-species of WOLF, since dog DNA and wolf DNA does not vary significantly at all, not enough that dogs can be granted separate species status. They are the same animal, one being the naturally-occurring fore-bearer of the other. There is no evidence to suggest than dogs result from any other canid species besides Canis lupus.

A hybrid is the cross between two distinctly DIFFERENT, yet related, species, species which once shared a common ancestor, but which have diverged enough genetically to warrant separate status. Very often, part of those differences involve different numbers of chromosomes, hence a hybrid offspring usually will have an odd number of chromosomes, rendering it infertile and incapable of reproduction, or else one gender will be sterile, meaning that the next generation, after the first-generation cross(designated as "F1"), will be the F2 generation, and will have to result from crossing a member of the fertile gender with a member of one of the two original species used to get the F1 generation. Usually, if the original F1 cross involves a wild and a domesticated species, the next generation, or F2, cross, will result from crossing a fertile F1 animal back to a domesticated animal, since the goal is usually to get more docile and controllable animals that have the appearance of a wild animal that many people still find pleasing. An example of a true sterile hybrid would be a mule, the offspring of a male donkey(Equus assus) and a female horse(Equus ferus caballus). Horses and donkeys differ enough that they are classified as separate species, and have different chromosome numbers, so mules cannot reproduce. An example of the other type of hybrid, in which one sex of the F1 cross is fertile(the female, in this case), would be the Bengal cat. The first generation of Bengals are created by crossing a male Asian Leopard Cat(Felis bengalensis) with a female domestic cat(Felis catus). All males of the F1 generation, and 75% of males of the F2 generation, are sterile, and with each successive generation of crossing back to a domestic cat, the percentage of fertile males increases.

Since wolves and dogs are the same species, there is NO SUCH THING as a "wolf hybrid"! The proper term for cross between a domestic dog and a wolf is a "wolfdog". There are no "breeds" of tarantulas, because there are none which have been selectively bred for specific characteristics by humans, that distinguish them from the original wild phenotype.

pitbulllady

 

[lancej]

Since wolves and dogs are the same species, there is NO SUCH THING as a "wolf hybrid"! The proper term for cross between a domestic dog and a wolf is a "wolfdog".

pitbulllady

I used to get into arguments with seemingly intelligent people about this! They would insist that since a wolf was a wild animal and a dog was domesticated, then it HAD to be a hybrid. Nowadays, if they don't get it when I explain what the definition of a hybrid is, I just grin and change the subject. I have learned that when it comes to dealing with people, it's just like Ron White says: "You can't fix stupid!"

 

[pitbulllady]

I used to get into arguments with seemingly intelligent people about this! They would insist that since a wolf was a wild animal and a dog was domesticated, then it HAD to be a hybrid. Nowadays, if they don't get it when I explain what the definition of a hybrid is, I just grin and change the subject. I have learned that when it comes to dealing with people, it's just like Ron White says: "You can't fix stupid!"

Even governments do not get it. Michigan recently enacted a state-wide ban on "feral swine" and "HYBRIDS of feral and domestic swine", which would be laughable if it hasn't had some really bad repercussions for innocent farmers. Domestic hogs are the EXACT same species as THEIR wild ancestor, the Eurasian wild boar, Sus scrofia. A feral animal is simply a domesticated animal that has escaped human confinement and returned to living in a wild state. Mustangs are feral horses, dingoes are feral primitive dogs, etc. In Michigan, it's illegal to own any hog(not including Pot-Bellies and other "miniature" breeds, mostly affects meat hogs)that is any color other than white, basically, or which has thick hair(DUH! ANY hog living in Michigan is going to develop thick hair due to their winters), has hair growing from the edges of its ears, or any of various other "signs" that it's mixed with "feral hog". That's like saying that you cannot own a horse that is part mustang! There is no such thing as a "hybrid hog", because all swine that can interbreed with domestic pigs are the same species as the domestic pigs!

pitbulllady

 

[lancej]

Even governments do not get it. Michigan recently enacted a state-wide ban on "feral swine" and "HYBRIDS of feral and domestic swine", which would be laughable if it hasn't had some really bad repercussions for innocent farmers. Domestic hogs are the EXACT same species as THEIR wild ancestor, the Eurasian wild boar, Sus scrofia. A feral animal is simply a domesticated animal that has escaped human confinement and returned to living in a wild state. Mustangs are feral horses, dingoes are feral primitive dogs, etc. In Michigan, it's illegal to own any hog(not including Pot-Bellies and other "miniature" breeds, mostly affects meat hogs)that is any color other than white, basically, or which has thick hair(DUH! ANY hog living in Michigan is going to develop thick hair due to their winters), has hair growing from the edges of its ears, or any of various other "signs" that it's mixed with "feral hog". That's like saying that you cannot own a horse that is part mustang! There is no such thing as a "hybrid hog", because all swine that can interbreed with domestic pigs are the same species as the domestic pigs!

pitbulllady

I really wish that I could say that I was shocked by this severe lack of intelligence in the general public. Unfortunately, the average person gets most, if not all, of their information from TV. It's very frustrating to think what it will be like for my children when they grow up. It doesn't seem like people will get it until every aspect of their lives is legislated to the point where it's illegal to make up their own minds.