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Tree's Leaves Genetically Different From Its Roots

samzenpus posted more than 2 years ago | from the different-parts dept.

Science 80

ananyo writes "Black cottonwood trees (Populus trichocarpa) can clone themselves to produce offspring that are connected to their parents by the same root system. Now, after the first genome-wide analysis of a tree, it turns out that the connected clones have many genetic differences, even between tissues from the top and bottom of a single tree. 'When people study plants, they'll often take a cutting from a leaf and assume that it is representative of the plant's genome,' says Brett Olds, a biologist at the University of Illinois at Urbana-Champaign who was involved in the study. 'That may not be the case. You may need to take multiple tissues.' The finding also challenges the idea that evolution only happens in a population rather than at an individual level. As one tree contains many different genomes, natural selection and evolution could happen within a single organism."

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Chimera Trees (0)

GameboyRMH (1153867) | more than 2 years ago | (#40973487)

And yet most fail to be monstrous or metal at all.

Uh... Howzat? (1)

Anonymous Coward | more than 2 years ago | (#40973519)

Are they saying some parts of the tree will survive to reproduce and other parts will not? I don't understand how "evolution could happen within a single organism."

Re:Uh... Howzat? (3, Interesting)

Russ1642 (1087959) | more than 2 years ago | (#40973623)

Sounds like that's what they're saying. Different tissues reproduce in different ways. For example a tree can make seeds or produce offshoots from the roots. One way could be more successful than another so areas with different genes within a single tree could produce a differing number of offspring.

Re:Uh... Howzat? (4, Interesting)

icebike (68054) | more than 2 years ago | (#40975373)

Well what they are really saying is that the upper parts of a tree can diverge from each other and from their root stocks via natural methods.

Any orchard owner knows that its easy to graft dissimilar branches on a common root stock, producing, for example, two different types of apples from the same tree. Its easy, and farmers have been doing it for years. Who knows where this idea arose.

Now it turns out that nature can do roughly the same thing, without all the cutting and splicing, but rather, by gene mutation or cross pollination or what ever.

Clearly every seed germinates to a single plant, but over time, it appears that significant divergence can take place on a single living tree. This might be a significant evolutionary advantage, as some branches may survive frost, drought, or pests better than other branches. A built in diversity in a single tree.

Perhaps we have to start thinking of some of these trees as colonies of organisms rather than a single individual.

Re:Uh... Howzat? (2)

pspahn (1175617) | more than 2 years ago | (#40976819)

Or, at a different level, consider how large colonies of trees can share the same root system, specifically the poplar family.

This would allow a shared root system to adapt independently of the trunks/limbs/leaves so that you get a root stock adapted to its specific soil type, while at the same time you get mutations up top which introduce better adaptations for the world above.

Trees are awesome.

Re:Uh... Howzat? (1)

Cuddlah (2677847) | more than 2 years ago | (#41014367)

Also consider that trees are continuously exposed to solar and cosmic radiation, and can live for many hundreds of years, and it's not hard to comprehend that mutations could have this effect of creating a large, complex organism that displays genetic differences between very old tissues and very young tissues.

Re:Uh... Howzat? (0)

Anonymous Coward | more than 2 years ago | (#40982467)

Perhaps we have to start thinking of some of these trees as colonies of organisms rather than a single individual.

Bingo. When the data doesn't fit the theory, you should question your underlying assumptions. But sadly that point isn't even considered here.

Re:Uh... Howzat? (1)

Captain.Abrecan (1926372) | more than 2 years ago | (#40985577)

Grafting and all that, as well as most genetic agriculture, comes from a monk who spent time splicing together different bean plants and breeding them. I can't remember his name, it's been a long time since I had a biology class. His work led to that square gene-expression thing we used to figure out with genes would be dominant. I'm surprised I remember any of that at all...

Either way, "As one tree contains many different genomes, natural selection and evolution could happen within a single organism." is a pretty bold claim.

Re:Uh... Howzat? (1)

icebike (68054) | more than 2 years ago | (#40985823)

I assume you refer to Gregor Mendel, [] but I have to point out that grafting had been used for centuries before he did his work.

Other things that were considered to be a single organism have turned out to be colonies of organisms. I believe there is s a type of fungus/mushroom in Wisconsin or Michigan that was found to be all connected under ground, and when taken as a whole ended up being the world's largest living organism.

We know some tree species have underground connected root systems, so its easy to mistake an individual tree for an individual organism.

The mystery here seems to be that nobody has nailed down the mechanism for differentiation within a tree. I could imagine one seedling (somehow) taking over the root system of another close relative species after a forest burned or something like that.

I agree it's pretty astounding.

Re:Uh... Howzat? (1)

PattyMc (1394421) | more than 2 years ago | (#40980829)

There are so many varieties of coleus because it is relatively common for a plant to produce a 'branch' that is of a completely different appearance from the the rest of the plant. Cut it off, root it and you have new strain. I don't know if the seeds from the new strain would revert to the parent, however. Now that we are looking, we may find that most organisms we think of as distinct are really co-ops. We have that part of the mind we think of as our self but there is that sub self which oft times seems to have a different agenda. A plant's top may have a slightly different agenda from its roots. In both cases there is cooperation but not slavish agreement.

Re:Uh... Howzat? (2)

Millennium (2451) | more than 2 years ago | (#40973663)

Trees can produce seeds almost anyplace they could produce leaves, so I don't think this really sounds all that far-fetched: something like that could happen. For organisms that have more centralized reproductive systems, it would be a lot more difficult.

Re:Uh... Howzat? (4, Informative)

fuzzyfuzzyfungus (1223518) | more than 2 years ago | (#40973883)

But not quite impossible, interestingly.

So called Clonally transmissible cancers [] are particularly growth-oriented cells from some progenitor organism that managed to beat the odds and, instead of just killing their luckless host as cancers tend to, spread to other members of the species.

There is also Henrietta Lacks; but she lives more or less exclusively in laboratory environments and might not be said to count...

Re:Uh... Howzat? (3, Informative)

TheLink (130905) | more than 2 years ago | (#40974883)

I think it's more of immune systems than reproductive systems.

Trees do not have "active" immune systems like animals, that cause "transplant rejection". The tree needs leaves and it needs roots, but as long as the leaves do reasonably "leafy" stuff they could be genetically different and the rest of the tree will go on fine. That's why you can often graft the top of one tree species onto the bottom part of another tree.

In contrast it's not trivial to put a related human's kidney into another human. You'd likely still have to suppress the immune system.

It could be because a tree doesn't need as much per in terms of resources (energy etc) per mass/volume, and it doesn't need to move. So some inefficiencies due to "cancer" (strange growths) are less likely to kill the tree. Thus it does not need to kill cancer as urgently.

Whereas strange growths are likely to kill you - once they are large enough so you can't move about, feed or breathe you're going to die.

Re:Uh... Howzat? (1)

biodata (1981610) | more than 2 years ago | (#40975355)

It's not just the large growths that kill you either, often it is the proliferation throughout the circulatory system. I don't know if anyone has ever seen this in plants - tumeruos tissues spreading by circulation.

Re:Uh... Howzat? (2)

the biologist (1659443) | more than 2 years ago | (#40980105)

Plant cells are unable to move about and so any cancer will be self-limiting. When the local tissue growth outstrips the food supply, the tissue dies and that is the end of the plant cancer. There are infectious plant cancers that are triggered by bacteria which hitch a ride inside things like aphids, as well as others which are triggered by the growth of fungus. In all cases it is another organism which is spreading and causing locally cancerous plant tissue to form.

There are plants which live as parasites in other plants, by growing their tissues through the host plants' tissues... but they had a long evolutionary history separate from their hosts to figure out ways to do this.

Re:Uh... Howzat? (3, Insightful)

Anonymous Coward | more than 2 years ago | (#40975719)

While that is a good point, that an active immune system would prevent genetic diversification within an individual, the diversification alone is not sufficient for evolution within an individual. For example, if you had some chimeric human where your arm had genetic differences from the rest of you, regardless of how viable or not the abilities of your arm are, that genetic material will not get passed on (some slashdotters should have experimentally figured out by now that hand-person relationships do not produce viable offspring). The only impact the genetic material in the arm could have is to promote or restrict the genome possessed by the reproductive organs.

In principle, a tree branch can compete with another branch in the same tree for light, nutrients, and be capable of producing its own seeds. Or at least it could produce more branches from its side of the tree, unlike say an organ in more complex animals being able to produce more organs if successful enough.

Re:Uh... Howzat? (1)

TheLink (130905) | more than 2 years ago | (#40981713)

That's a good point too. Each part of the tree is more independent from the rest when compared to the more complex animals.

Chop off a branch, stick it in the ground under favorable conditions and it might become a new tree. It takes amazingly "favorable" conditions to do something similar with humans (aka cloning)...

Re:Uh... Howzat? (5, Interesting)

Anonymous Coward | more than 2 years ago | (#40973747)

Actually, yes. That's exactly it. Think about the times you've seen a tree with a plenty of leaves, but with dead branches mixed in.

Given the way that trees grow, this actually makes sense. Tissues in the trunk are only grown in a very narrow band located between the bark and the wood. If a mutation happens at some point during the tree's growth, it's possible that the new tissues will be more/less likely to survive given the current environmental circumstances. Those new tissues carrying beneficial mutations would be more common as the tree continues to grow. Leaves are an even more extreme example. If a given branch has tissues with a given mutation, the leaf buds on the tree will carry it, and the leaves will carry it. Branches with more productive leaves will live longer/better as a result. Given that trees can grow for hundreds of years, it's possible that the same tree may have had dozens of mutations in its genetic structure some of which were passed on to branches at different points in time, multiple of which could still be 'active' as a result.

This is less likely to be the case for animals, since their tissues undergo complete replacement over a comparatively short period of time. That means a genetic sample from an animal would almost always only reflect the *current* genetic state of the animal.

Re:Uh... Howzat? (1)

Jason Levine (196982) | more than 2 years ago | (#40974677)

Thinking of it this way, studying a single large tree (at multiple points along its growth) might reveal a lot of interesting information about how evolution works. As you head from the tips of the branches to the trunk and leaves, it would be like looking back in time.

Re:Uh... Howzat? (3, Interesting)

Rhaban (987410) | more than 2 years ago | (#40973817)

A mutation could happen in single cell, ar a group of cells during the tree growth, and then a leaf or an entire branch spawns from this cell.

If cells in tree nodes are for some reason likely to be the subject of mutations, it's easy to imagine natural selection occuring at a cell level, with a branch growing from the fittest cells.

Re:Uh... Howzat? (0)

Anonymous Coward | more than 2 years ago | (#40975967)

A human being, for example, is a single organism that is composed of multitudes of cell colonies. Those cell colonies could compete and respond to a fitness function while still being part of a "single organism." In fact, plenty of that is going on inside your body right now!

An "Organism" is just an imaginary dotted line that our minds draw around a piece of the observable universe. When that line is big enough, it will be easy to find evolution going on inside of it.

tree grafting is common practice (3, Interesting)

RichMan (8097) | more than 2 years ago | (#40973537)

The grafting of fruit trees is very common.

There are other advantages to grafting. A grafted fruit tree may be made to grow in new places. A peach likes sandy, wellsanded soil. The plum tree likes poorly drained soil. Peach can be grafted onto plum stock growing in soggy soil. Plum can be grafted ,into peach stock growing in looses sandy soil. So we get peaches and plums growing where they have never grown before.

Grafting also helps to keep down plait pests and disease. Some fruit trees cannot be hurt by this pest or that disease. These trees form fine stock, though the fruit may be poor,.

Yes, it is. (1)

intellitech (1912116) | more than 2 years ago | (#40973615)

Taking cuttings from plants in general is even more common.

I'm curious to see these examinations performed on a larger variety of plant types and species..

Re:tree grafting is common practice (1)

cygnwolf (601176) | more than 2 years ago | (#40973709)

But completely irrelevant to the article. This is talking about own-root trees.

Re:tree grafting is common practice (0)

Anonymous Coward | more than 2 years ago | (#40974933)

It's not irrelevant. Since if the top of the tree is genetically different from the bottom, it starts to look less "own root" ;).

Re:tree grafting is common practice (3, Interesting)

bennomatic (691188) | more than 2 years ago | (#40974951)

Maybe not completely irrelevant. Perhaps, in a given population of a species of tree, there is not only cross-pollination, but also cross-grafting. Maybe insects or higher animals move leaves or seeds from tree to tree, and for some reason, this species is more likely to accept the new introduction without complex grafting techniques.

To wit: Tree A spawns tree B through pollination with tree C, so B is indeed genetically unique. B is close to A, though, and a bird gathering shoots for its nest brings over something viable from B to A and sticks it in the crook of a branch and it grafts. B' is born, effectively a grandchild AND parasite of A.

I'm just letting my imagination wander here, but it certainly would be interesting if that were the case.

Re:tree grafting is common practice (1)

pspahn (1175617) | more than 2 years ago | (#40976917)

Not necessarily.

If you ever look at a large nursery catalog, you may see that a specific apple tree is available with a variety of root stocks (often patented/trademarked). These various root stocks aren't necessarily from different species of trees, but instead come from different cultivars of that same tree.

What you end up with is the ability to buy a truck-load of apple trees with an apple root stock that has adapted to better survive cold winters (at the expense of larger fruit, for example).

Re:tree grafting is common practice (0)

Anonymous Coward | more than 2 years ago | (#40974189)

I guess the apple does fall far from the tree.

Re:tree grafting is common practice (1)

misterscience (2691159) | more than 2 years ago | (#40976525)

Grafting of fruit flies less so.

Re:tree grafting is common practice (1)

ChromeAeonium (1026952) | more than 2 years ago | (#40977857)

I was thinking more of the bud sports used in grafting. Sometimes plants produce a branch with a spontaneous mutation that has a useful trait, like an apple that fruits differently, a pale grape, or an earlier peach. These mutants are grafted for their useful traits, and because of this, even though there is only one umbrella variety, like Gala [] , there can be multiple different strains of sports used in different orchards (like Gale Gala or Ultima Gala). I don't see how something horticulturalists have been taking advantage of for who knows how long is news.

4 more years for Obama (-1)

Anonymous Coward | more than 2 years ago | (#40973541)

Thank, Mitt. Nice fucking pick.

ugh (0)

Anonymous Coward | more than 2 years ago | (#40973651)

offtopic :trollface:

can we (0)

Anonymous Coward | more than 2 years ago | (#40973559)

can we show a image of all the bugs and bacteria that grow on plants want to give these meat haters some squirming....
OH and post how much is in our guts we need to have to live .....


Re:can we (1)

jellomizer (103300) | more than 2 years ago | (#40973719)

They will show all the bugs and bacteria that is in meat.

Face it we are very disgusting animals.

Re:can we (1)

LeadSongDog (1120683) | more than 2 years ago | (#40973853)

Face it we are very disgusting animals.

Sounds like you need to toughen up your sense of disgust. It's eat or die. Think like a vulture, they're the ultimate conservationist animals, though of course they've got nothing on fungi.

Re:can we (1)

TheLink (130905) | more than 2 years ago | (#40974961)

Fungi are the ultimate in recyclers. There's a theory that those large coal deposits exist because back then the fungi hadn't evolved to digest dead trees yet.

Re:can we (0)

Anonymous Coward | more than 2 years ago | (#40974935)

Human body: 10tril human cells
Human body: 100tril bacterial cells

Even in our own body, there is more bacteria than us, by pure numbers.

Show that to those crazy people

Re:can we (1)

jc42 (318812) | more than 2 years ago | (#40977057)

Human body: 10tril human cells Human body: 100tril bacterial cells Even in our own body, there is more bacteria than us, by pure numbers.

Well, yeah, by cell count. But our cells average about 10 times the diameter and 1000 times the volume of the typical bacterial cell, so by mass we're only around 1% bacteria. (And these numbers are only accurate to 1 decimal place; you may be 2% bacteria by volume. ;-)

Cell count and total volume/mass are both valid measures of "size", of course, though they mean rather different things.

It's also occasionally pointed out that most of the biomass on our planet is in the form of bacteria (and archaea). Multi-celled creatures like us (and trees) are a tiny portion of the world's total biomass, whether you use cell count or mass or volume.

Re:can we (0)

Anonymous Coward | more than 2 years ago | (#40973753)

The same applies to meat though.

Re:can we (1)

dlingman (1757250) | more than 2 years ago | (#40975079)

But isn't bacteria, technically, made of meat as well?

Re:can we (1)

TapeCutter (624760) | more than 2 years ago | (#40978683)

No, meat is muscle cells from an animal or fish, muscle cells are not bacterial cells.

Re:can we (0)

Anonymous Coward | more than 2 years ago | (#40990645)

Not by most people's definition of "meat". Meat consists of muscle fiber, fat, and sometimes bone, or complex organs such as heart, liver, etc. Bacteria are none of these.

It's one reason why good meat substitutes are so hard to make. It has to have the texture of meat. Nobody wants a meat milkshake.

evolution could happen within a single organism. (1, Funny)

fustakrakich (1673220) | more than 2 years ago | (#40973683)

Yeah, but I bet it has a lousy sex life.

Say what? (2)

Hatta (162192) | more than 2 years ago | (#40973695)

The finding also challenges the idea that evolution only happens in a population rather than at an individual level. As one tree contains many different genomes, natural selection and evolution could happen within a single organism."

Nobody ever thought that. Evolution happens with any sort of imperfect replicator subjected to selection. Period. A good example of this happening within our own bodies would be cancer.

Re:Say what? (2)

timeOday (582209) | more than 2 years ago | (#40973941)

From the article:

The findings have parallels to cancer studies. Earlier this year, scientists showed that separate parts of the same tumour can evolve independently and build up distinct genetic mutations, meaning that single biopsies give only a narrow view of the tumour's diversity

However, it seems to me that cancer mutations are usually not germline, whereas these mutations in trees might well be... dare we use the term "Lamarckian"?

Re:Say what? (1)

ilguido (1704434) | more than 2 years ago | (#40974513)

However, it seems to me that cancer mutations are usually not germline, whereas these mutations in trees might well be... dare we use the term "Lamarckian"?

Poor Lamarck, after a century of darwinism his time has come.

Re:Say what? (1)

the biologist (1659443) | more than 2 years ago | (#40980127)

The cancer mutations are definitely germline, for the cancer itself.

Re:Say what? (1)

ChronoFish (948067) | more than 2 years ago | (#40974675)

You could argue (I would) that even in this example of trees (and of cancer) that evolution IS the change of populations over time. Our bodies and those of trees are made up of a population of cells. The cells genetics changes due to a number of factors, and the those changes can be replicated to new cells. Cancer is the perfect example of this in our own bodies. Now it seems that Tree's go through this as well.

It would be interesting to see if the evolution of cells in a tree keeps the tree population relatively static, Vs. if the homogeneous make up of animal cells made them more prone to rapid change at the population level.


Re:Say what? (1)

mcgrew (92797) | more than 2 years ago | (#40975129)

Have you ever read Asimov's Playboy and the Slime Gods? [] The aliens in that story reproduce asexually, which Asimov (a biochemist who did cancer research at Boston University) figured would evolve very slowly. Unfortunately (or fortunately if you want to actually read the story in the book Nightfall) the wikipedia synopsis is awful offal.

Re:Say what? (2)

I(rispee_I(reme (310391) | more than 2 years ago | (#40976077)

Those who want to read it need not settle for a wikipedia editor's summary.

The story was originally printed in the March 1962 issue of Amazing Stories. Scan available here [] .

Also, Asimov's original title for the story, "What Is This Thing Called Love?" is restored in his short story collection, "Nightfall and Other Stories".

Re:Say what? (1)

mcgrew (92797) | more than 2 years ago | (#40983943)

Thanks for the link to the scan, I didn't know any of his works were online. "Nightfall" is one of the two dozen books in my Asimov collection. I wish I had copies of all 500+ of them!

Re:Say what? (1)

mcgrew (92797) | more than 2 years ago | (#41005165)

I went to your link and saw nothing but advertising.

Cancer (3, Insightful)

Dachannien (617929) | more than 2 years ago | (#40973725)

That's essentially what cancer is, a genetic mutation in a cell that evolves it into an undying, eternally reproducing organism that parasitically gets its nutrients from its host organism/ancestor.

Re:Cancer (2)

LeadSongDog (1120683) | more than 2 years ago | (#40974039)

Well, cancers aren't very good at hijacking the reproductive mechanisms to make immortal babies. (SF plot idea, anyone?) There are lots of viruses and even bacteria that will do things like that. Ticks pass Rocky Mountain spotted fever to their eggs. River blindness is a bacterium passed by nematodes through biting flies and humans that give a reproductive advantage to the flies from the bug they carry. Malaria promotes the reproduction of the mosquitos that carry it (in competition with uninfected mosquitos).

Re:Cancer (4, Informative)

wierd_w (1375923) | more than 2 years ago | (#40974833)

Not entirely true.

There exists a naturally occurring "disease" in dogs that is a sexually transmitted cancer. []

It could be considered a highly successful parasitical mutation of the canid genome, which has evolved to make use of the reproductive behaviors of its host organism to perpetuate itself.

IIRC, genetic analysis of the genome for the tumor suggests that it is several thousand years old.

Re:Cancer (1)

LeadSongDog (1120683) | more than 2 years ago | (#40975401)

That CTVT example is one of just three TVTs, which rather makes my case. But the real point is that TVTs don't help the host propagate better, just the tumor. They're purely parasitic, not symbiotic. In that sense, they're less successful adaptions than malaria, RMSF, or river blindness are.

Re:Cancer (1)

TapeCutter (624760) | more than 2 years ago | (#40978815)

The Tasmanian devil population is currently suffering through a plague of transmissible mouth cancers, from reports it appears to be a relatively new disease, not sure how it is transmitted though.

Re:Cancer (2)

the biologist (1659443) | more than 2 years ago | (#40980241)

Analysis of the tumors suggests it was derived from a Schwann cell tumor. The transmission is mediated by the tendency for Tasmaninan Devils to bite each other on/around the head in their frequent and loud squabbles.

The few other observed transmissible cancers cover a range of mechanisms (venereal [] ; mosquito [] ).

Re:Cancer (0)

Anonymous Coward | more than 2 years ago | (#40974869)

There are sexually transmitted cancers (and I don't just mean cancers caused by viruses that are sexually transmitted):
canine transmissible venereal tumor

Re:Cancer (2)

Hentes (2461350) | more than 2 years ago | (#40974109)

Evolution is a combination of mutation and selection, the latter which isn't really present in cancer because it is a product of a single dramatic mutation, not normal cells slowly evolving into cancer cells. It couldn't have a continuous evolution anyway for its time is limited: either it dies or its host, killing both of them. Clonal tree colonies, on the other hand, can live for eternity.

Re:Cancer (1)

Daniel Dvorkin (106857) | more than 2 years ago | (#40974717)

Depends on your POV: you could think of potentially cancerous cells as being species of one-celled organisms, with the successful ones being those which go on to form actual tumors, which do of course reproduce within the body. Eventually, they do kill the host and thus themselves, but this is really no different from a species going extinct when it uses up the resources available in its local ecosystem.

Re:Cancer (0)

Anonymous Coward | more than 2 years ago | (#40975231)

If cancer is a genetic response to environmental cues, as much research leads us to believe, then it's expression is based on preexisting definition which has successfully been passed, through sexually recombination, from one generation to the next. However it does not help the species to survive, unless there is an advantage to 'early' death. It is either an artifact without evolutionary advantage, like your appendix, or it is a trait, the value of which we may be loath to acknowledge. Perhaps one tied to the advantage of the limited lifespan it helps ensure.

After all, in a finite world with limited resources, immortality would have resulted in a state of global population long before man ever had the opportunity to develop complex technologies. Thus the importance of symbolic representation of local knowledge. Without the written word and its ability to convey data, information and knowledge from one generation to the next, we would never have the opportunity to develop with wisdom we need to avoid our own extinction.

Perhaps we owe cancer a debt of gratitude. As medicine holds the ability to keep all of us alive for longer spans, even as we are reaching for the carrying capacity of the Earth, cancer occurs with increasing frequency, for reasons we do not seem to understand.

Re:Cancer (2)

wierd_w (1375923) | more than 2 years ago | (#40975147)

The sexually transmitted cancers, like canine venereal tumor, move from host to host before being destroyed by the host's immune system. This places it firmly in the realm of natural selection for reproductive fitness:

It has to easily detach from the host tissue.
It has to easily integrate into the new host tissue.
It has to withstand the host's immune response for extended periods until it can reproduce itself in a new host.

This, in addition to energy consumption fitness and other evolutionary pressures.

Normal cancers cant make that claim, but transmissible ones can.

Re:Cancer (1)

pscottdv (676889) | more than 2 years ago | (#40974661)

That's essentially what cancer is, a genetic mutation in a cell that evolves it into an undying, eternally reproducing organism that parasitically gets its nutrients from its host organism/ancestor.

Cancer is caused by a small number of mutations and does not behave in a way that is healthy to the entire organism. These cottonwood trees, on the other hand have "variation within a tree... as great as the variation across unrelated trees" all within a healthy organism.

Some monkeys are similarly troublesome... (4, Informative)

fuzzyfuzzyfungus (1223518) | more than 2 years ago | (#40973759)

Some marmosets [] are naturally chimeric some substantial portion of the time. This leads to wacky fun for researchers because it is perfectly possible(depending on how the different cell populations ended up distributed in the mature monkey) for an individual to show one genotype on blood tests; but produce offspring that appear to be genetic descendants of their brother or sister....

Just to be sure, we'll probably have to homogenize any animals and/or small children we wish to study in the future. []

Re:Some monkeys are similarly troublesome... (5, Informative)

wonkey_monkey (2592601) | more than 2 years ago | (#40974351)

And if anyone's wondering, it happens in humans too. One woman [] nearly had her kids taken away when DNA tests indicated she wasn't their mother, until it was determined that her reproductive system was from one of her constituent maternal "twins" while her hair and skin (which were sampled for the tests) were from another.

Mmmm... soup-like homogenate...

In my opinion, (1)

inquist (2489806) | more than 2 years ago | (#40973899)

This is one of the coolest things ever.

2 means of reproduction; 2 genomes (1)

misterscience (2691159) | more than 2 years ago | (#40973913)

No big surprise that an organism that reproduces by seed as well as by rhizome cloning has evolved two distinct ways of coding these strategies. I would not be surprised if many plants that reproduce underground like this have tailored their genes to do so.

What about humans? (1)

tompaulco (629533) | more than 2 years ago | (#40974343)

I wonder if they did a sample from a toe and a sample from the head if they would come up with different genetics. My assumption would be that there would be slight differences.

Re:What about humans? (2, Interesting)

Anonymous Coward | more than 2 years ago | (#40974827)

The current theory, is that you would not in a "normal" human. The gene sequences should be identical in all healthy cells, with only the pattern of currently active genes changing between cells. Mutations later in life tend to result in cancer, not functional human tissue.

However, there are known ways for this to not be true. Typically it has to do with the subject having absorbed siblings while in the womb. It would be interesting to find out how common that actually is in humans.

Re:What about humans? (0)

Anonymous Coward | more than 2 years ago | (#40976543)

A human cell introduces some number of mutations when it divides. The number is uncertain; some put it at around one, some at 100+. Most of these are in non-coding DNA; at the upper bound, one or two mutations are in actual genes (the coding, non-junk part), and since all genes are not activated in all cells (cells in your eye may not need to synthesize proteins used in your skin), even differences in genes can result in nothing happening. And then many mutations result in the same protein (see codon aliasing) or a protein that is close enough not to matter. So yes, you should find quite a few differences between your own cells. Google for: human cell division mutations.

Paraphrasing the Jurassic Park novel (2)

GodfatherofSoul (174979) | more than 2 years ago | (#40974783)

People think that nature is a bunch of animals running around a green backdrop. But, plants have their own pretty interesting evolution. I took a botany class in college and it gives you a whole new appreciation for the "scenery" in your nature documentaries.

Re:Paraphrasing the Jurassic Park novel (1)

TapeCutter (624760) | more than 2 years ago | (#40979085)

The time I appreciate plants the most is when a drought breaks, we had a deep and long drought here in Oz recently that lasted several years. My house is near the beach so for most of that time the yard was just bare sand. When the drought broke a couple of years ago, somehow the grass "knew" and instead of coming up in patches like it did after a storm during the drought, it came up like a carpet of barely perceptible green fuzz, within a month the city had their lawn mowers out again. I've been through several droughts and seen the greenery come back in spectacular fashion, but this one I noticed very early and the speed and synchronicity of the response blew me away. Looking at those tiny green-yellow shoots push up through the desert sands in my yard really made me appreciate just how tough ordinary grass is.

Shades Of Those Other Amazons (1)

rmdingler (1955220) | more than 2 years ago | (#40975057)

With innovations in the introduction of parthenogenesis to new species' perhaps this discovery is good news for only about 50% of the population.

This is news? (2)

tilante (2547392) | more than 2 years ago | (#40975663)

I'm sure that I remember reading about most trees being genetic mosaics more than ten years back. And I know for certain that I heard about a case of it happening in people at a conference on Neurofibromatosis more than ten years ago.

(Presentation at the conference had a bit about a family where several of the children had NF Type 1, even though neither of the parents did. NF1 is a genetically dominant mutation, but having two copies of the gene is lethal -- thus, if one parent has NF1, you expect that roughly half the children will... but if neither parent has it, the chance of a child having it should be very small. In this case, though, about half the children had NF1, even though tests said neither of the parents had the gene.

Eventually, it was discovered that part of the father's body had NF1 -- including the testes. Most of his body, however, did not have the gene. Thus, while tests using cells taken from other parts of his body showed him as not having NF1, for reproductive purposes, he did.

As I recall, at the time, the prevailing belief among the geneticists working on the disease was that neurofibromas - lumps on the nerves associated with NF1 - were themselves manifestations of cellular-level mutations. Essentially, when a nerve cell in the body mutated in such a way as to lose its working copy of the NF1 gene, a neurofibroma resulted. Not sure if that's still what's believed, though, since that was over a decade ago.)

As Carl Sagan said (1)

lt.cyx (1376331) | more than 2 years ago | (#40975985)

'How lovely trees are.'

Evolution Of A Population? (2)

Kozar_The_Malignant (738483) | more than 2 years ago | (#40976245)

> The finding also challenges the idea that evolution only happens in a population rather than at an individual level.

I'm not sure where this statement comes from. Evolution by means of natural selection has always been understood to act at the individual level. You are favored in reproduction or not. There are all kinds of nifty mathematical ways to describe the effect of this on populations that lead to talk of "populations evolving," but that is a sloppy way of describing the cumulative effect of individual evolutionary events.

Possible resistance to fungi and insects? (1)

climb_no_fear (572210) | more than 2 years ago | (#40976827)

Maybe a plant biologist could weigh in here but I wonder if this diversification couldn't lead to different parts of the plant being more or less resistant to various pests? I mean, these trees get pretty old so it seems like a good way to ensure survival of the whole tree since some parts of it may have resistance. Also, if the tree is hermaphroditic (sorry, I don't know enough about cottonwood to know) the resistant parts could cross-fertilize, resulting in seeds potentially even more resistant, right? Would be interesting to see if they are different enough to eliminate self-incompatibility []

It happens in you! (1)

robi5 (1261542) | more than 2 years ago | (#40977243)

The human brain itself is famous for its mosaic aneuploidy (, which is similar to having different genes in that the number of chromosome copies have a lot of gene expression significance (think of trisomy 21, for example). So as wonderful it sounds, it's nothing out of the ordinary. In biology, you can start research by going against something like the central dogma and finding counterexamples. Retrovirus, platypus, photosynthetizing animals ad nauseam. Also, as radiation causes mutation, presumably at the cell level, it would be a small wonder if genes were the same in a multibillion-cell organization.

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