DNA research is turning the morphological taxonomy of species on its ears. Biologists at Berkeley have uncovered a whole new family tree for hundreds of salamander populations thought to be members of the same species. The same general reorganization of existing taxonomic schemes may be indicated in other families. The explosion of new information from genome research is redrawing the entire tree of life.
Of course the fact that the answers we have are wrong only means that we have incorrectly applied the information of morphology to widely separated populations of critters, and assumed them to be of the same species. It becomes more and more clear that the final word on what constitutes a species is degree of shared genetic heritage, and divergent DNA characteristics. That comparison will become the general rule over the coming decades, as the type of testing which it requires becomes more common in field biology.
Forgive me the tongue in cheek topic title, please, but it was just too tempting to forego.
Tris
“Human beings are the only creatures that allow their children to come back home.” ~ Bill Cosby ~
After reading the linked article, it seems as though one of the causes of this underrepresentation of species diversity might be the common practice of not assigning a new species designation to members of two populations which could theoretically interbreed, but don’t because of geographical barriers (per the Biological Species Concept). Perhaps Mayr had it wrong, in that “potentially” interbreeding populations are not necessarily the same species - if they aren’t interbreeding, they may be well on their way to being distinct, if they are not already. This could also mean that true speciation happens much more rapidly (and subtly) than previously thought…
The only way to settle this would be to do DNA tests of every population of every animal that exists in seperate zones. Then we can have a complete picture. Unfortunately, that would probably cost billions in time, collection, and research. A random “shotgun” approach to picking species that have a possiblity this could happen would be more cost efficient, but might leave an important group excluded.
Actually, Tars, I think that in a non-monolithic fashion that is exactly what will happen. It will eventually become a standard practice to examine DNA in every biology sample. That information will become widely available over time. In the future, the correlation of different samples will be a field of study done by students in search of material for doctoral thesis work. The eventual mapping of the genome of all life on earth will not be the work of one project, but the results of a century or two of work by lots of people, seeking different goals.
Tris
“The difference between a violin and a viola is that a viola burns longer.” ~ Victor Borge ~
Actually, I had read about this study in Science, and had wanted to start a thread about it but couldn’t link to the Science website. To wit, the salamander species in question is clearly evolving into a snakelike creature, and is, therefore, an example of a present-day “transitional form” like the creationists keep pestering us about.
BTW, there was another article on the “tired light” hypothesis so beloved of YEC’s. The final nail has been driven in the “tired light” coffin, because distant stars have been shown to be experiencing relativistic time dilation, which would result from high-speed motion but not from tired light.
I’ve read that based on genetic studies and the isolation of populations, what’s now considered one species of chimpanzee (not counting the bonobo) should be counted as two, or at least two sub-species. And ditto for the orangutan, which some people are saying that zoos should not interbreed the two varieties in order to preserve their uniqueness.
Just IMO, but it’s this kind of slapdash playing with the facts that makes some folks very wary of other fundamentalist claims, such as Creation “Science”.
You can only imagine how distraught I am that my “other fundamentalist claims” will be deleteriously affected by this slapdash playing with facts.
Oh! Watch out! Duck! There goes a clue! They are almost extinct, you know.
Tris
“It should be possible to explain the laws of physics to a barmaid.” ~ Albert Einstein ~
“Man, you should have seen the place where Einstein used to go drink!” ~ Triskadecamus ~
Once again, we have a question of competing species concepts . The problem with a lot of these “crypto-species” is field workers hate’em because it makes taxonomy a pain in the ass. However evolutionary biologists seem to increasingly prefer the more historically informative approach taken by Wake, et al. So what we have, sort of ( and only sort of ), is the “pragmatists” vs. the “idealists”.
There was some discussion on this topic in this thread recently:
Towards the bottom of that page there I have a few interesting links vis-a-vis species concepts.
Tamerlane
p.s. - Darwin’s Finch : Regarding that old discussion - Re: Mayr and his view of parthenospecies under the BSC - I was just rereading a section of Toward a New Philosophy of Biology. He does in fact recognize that the the BSC doesn’t work for clonal organisms. Instead he proposes a separate category for them - Such as “paraspecies”.
Tamarlane: Upon re-reading some cladistics work by Eldredge (of punctuated equilibrium fame), I “remembered” that I don’t particularly care for the BSC myself The salamander issue, as well as the snakes you mentioned previously, seem to support the idea that the BSC is being misapplied, even if it might be (more or less) sound in theory (with obvious limitations, of course).
I’m all for DNA testing and such to determine phylogenetic trees; the problem is that it becomes decreasingly useful the further back one goes through the fossil record (and, of course, it doesn’t work at all on trace fossils). So, with respect to those trees, we’ll likely find ourselves with a nice bushy top canopy, but the further down we go, the less defined the relationships get. Of course, that’s what we have now, so I guess it won’t be any different
Maybe, by examining the genetic origins, we may find other ways of identifying species’ origins that do not demand genetics, allowing easier species placement. I have no idea what such traits could be. Also, like Triskadecamus said, i think someday every species will be sequenced, but until rapid sequencing software and techniques are available, the cost will be ridiculus (i’m doing sequencing right now, as we speak, so i am familiar with costs). One day we will be able to put a sample in a machine and get a complete readout, which will probably be standard fare to do when we reach other worlds (off on a sci-fi tangent here), but by the time we get it here, we will have many species already done the old fashion way.
Does anyone know what species are bing sequenced currently? I have heard of Human, E. coli, Fruit fly, P. falciparum (malaria, i think thats the species), and mouse off the top of my head, there must be dozens of others.
Well, the mouse is the only remaining member of the “security council” not fully sequenced yet: Human, mouse, drosophila, arabidopsis (a mustard,) yeast, E. coli, and C. elegans (a nematode worm.)
There are a lot of non-council organisms that have been sequenced, or are being sequenced: malaria, cholera, rice, TB, and (IIRC) some myxoplasmas and some extremophiles (Methanococcus janaschii, perhaps? I don’t remember.)
A number of virus genomes (AIDS, bacteriophage lambda, etc.) have been available for a while now.
A scientist at Duke University Medical Center has published an article (linked to ScienceDaily.com) in the journal Molecular Genetics which shows that even gene sequencing provides some perils in assigning taxonomic designations. Mitrochondrial and Nuclear genetic information have varying degrees of statistical reliability in predicting descent among species.
Just keeping up with the basics is becoming a full time education. Fighting ignorance is gonna get really tough, when the amount of stuff you can be ignorant about gets bigger so fast!
Tris
“It is even harder for the average ape to believe that he has descended from man.” ~ Henry Louis Mencken ~
Indeed, I think that is part of the problem when dealing with creationists (which is sort of related to this topic). Because there is so much specialized knowledge in a vast number of scientific journal articles, there is no one place we can point to and say, “There is your proof! Now leave us alone!” The local creationists I have been dealing with recently kept asking why the “proof” wasn’t in our little 8-page local skeptics group newsletter. I kept trying to explain to them this concept, but they just didn’t want to get it.
Anyway, yes, the more knowledge there is, the more ignorance there is as well…
Well, you see, it really only disproves (actually really only exposes some inconsistencies predicted by) a particular application of the principles which rely on the fundamental relationship between various species assumed to hold true under the model of biological classification consistent with the theory of evolution. But that is waaaaaay too long for a thread title.
I should go back to screaming to people that they are going to go to hell if they don’t burn their biology books. It’s so much simpler.
Tris
" It is when I struggle to be brief that I become obscure." ~ Horace ~
This whole area is relatively fascinating to me, as it is adjunct what I do in the lab every day (studying to be a molecular geneticist) and it is an area phenomenally unfamiliar to me… So it is 1:30, I am insomniac, and I feel like rambling.
My two cents are as follows:
The fossil record means much less to me than the current genetic record. Eyestalks on 1 square centimeter fossils from the Burgess Shale seem to be a relatively shaky account of when eyes came into existence, to name one of many problems. It seems (and I am very slanted as I work in molecular genetics) that structures can be very easily confused in paleontology. I studied osseology in medical school and boy if there aren’t a lot of knobs and projections and tubercules and condyles and stuff on the skeletal system, many for minor muscle attachments and strange movements which I failed to comprehend (and thus did only marginally well in anatomy…) Seeing a specific bone condyle and concluding an animal flew, is IM very HO a troublesome point.
The genetic record as I see it also has big problems. We don’t understand how mutation rates change. We don’t understand how large scale genomic reorganizations can happen so quickly. We don’t understand how most of our genome is structured (we have something like 40% retrovirally derived sequences making up our genomes). Things can adapt and speciate very quickly, as seen in Drosophila. This is often accompanied by large scale genomic change (which as I understand may form the basis of speciation). And of course we can only make predictions about the formation and divergence of gene families that no one has ever actually observed.
I think what will happen is that relevant portions of the genomes will be sequenced and molecular taxonomy will be the standard along with comparitive anatomy. It is already happening with things like the Pax6 cluster (on which I am pursuing a PhD), which is a large genetic component of eye development. When new species are discovered, I think it will be prudent to sequence certain divergent areas and categorize some slow-changing polymorphisms to try and describe speciation. Cross-referencing with comparitive anatomy or paleontology will give us ideas which elements in the skeleton and in the genome are most easily conserved and which are most easily changed. Hypothesis on why certain areas are or are not will be a new field of evolutionary science. Maybe a postdoc for me. Maybe not.
Since you seem to have a knowledge of genetics, I was curious as to how you answer “Haldane’s Dilema”? Haldane effectively showed that long-generation organisms have not had enough time to evolve, because of the cost of substitution (the fixing of a new gene in a population requires the death of those individuals which do not have it), even given assumptions favourable for evolution (for example, no pleiotropy or polygeny and only minimal consideration of recessive alleles).
Since you seem to have a knowledge of genetics, I was curious as to how you answer “Haldane’s Dilema”? Haldane effectively showed that long-generation organisms have not had enough time to evolve, because of the cost of substitution (the fixing of a new gene in a population requires the death of those individuals which do not have it), even given assumptions favourable for evolution (for example, no pleiotropy or polygeny and only minimal consideration of recessive alleles).
. The problem with a lot of these “crypto-species” is field workers hate’em because it makes taxonomy a pain in the ass. However evolutionary biologists seem to increasingly prefer the more historically informative approach taken by Wake, et al. So what we have, sort of ( and only sort of ), is the “pragmatists” vs. the “idealists”.