Evolution by Individual Trees

[Patchwork]

if a tree can mutate its own cells with hormones, dose that count as evoloution? i always wondered with symbiotic relationships (the one where the fungi is inside the tree cells rather than around them) what dose that class as? infection or mutation. sorry if i have steped into a thread that is way out of my league but this intrests me a great deal. could any one recoment any university courses that specifically deal with genetics of trees?

[ScottF]

Maybe this is being pedantic, but just for clarity's sake my understanding of what evolution is, is that it's the change in inherited traits from one generation to following generation via reproduction. I think what we're talking about in this thread is mutation which confers an adaptive advantage. Only one this advantage has been passed on to the next generation can it be called part of evolution. If you accept the conventional model of natural selection, then all of these mutations are totally random and it's very lucky if any adaptive advantage is achieved at all.

 

I don't personally believe in the conventional model of natural selection and favour the theories of "self-describing (autopoesis) systems" described my Capra and Marguilis is a really cool book called "The Web of Life".

[Amelanchier]

Sorry - I've been neglecting my own thread. Unforgivable.

 

Could that mean that ring porous trees are a successive adaptation to summer drought?

 

I would have thought ring porous trees (or at least those that can be said to remain ring porous most of the time) simply share a common ancestor that exhibited the adaption.

 

A lot of trees swap between diffuse and ring porous depending on age and environment. This hints that there is some kind of mechanism that instructs the cambium as it differentiates cells.

 

Now I'd say that that mechanism is the real adaptation that is of interest.

[Amelanchier]

Tony, is it not also possible that the top left twiggy limb bit has a better supply of nutrients than the rest of the tree, therefore retains its youthfull looks longer than the rest of the tree? Apart from that, this is waaaaaay over my head!

 

It's certainly possible Andy. Though a better supply line might not explain why it has ignore the chemical signals swimming around its vascular system telling it to prepare for dormancy. Maybe, the huge reduction cut nearby has something to do with it???

 

It was just a thought!!

[Amelanchier]

This is something that I am particularly interested in. Funnily enough it also came up on wendnesday on my tech cert course in relation to reiterations. Apparently a reasearch group in the tropics has proved that reiterations can be geneticly distinct.

 

I'd love to chase that up Phenom, if you get a chance, could you get a source???

 

When I was at University I did an experement where I tried to disprove the genetic mosaic Hypothysis. I measured various dimensions of hazel nuts and there cupules, recording which branch they came from and which tree. I measured thousands of hazelnuts in the Burren in Ireland. Then I ran a nested analysis of variance on the data set.

 

We found that you could accept that there was variety within trees and between trees. But that somatic variation was less than variation caused by sexuall recombination.

 

Hazel nuts where chosen because the nut is not influenced by the pollen that fertilizes the ovule (it is derived from the ovum) and because of its importance to the plant its form is not effected by environmental factors.

 

Obviously there are many flaws to this experiment when it comes to addressing the Genetic mosaic Hypothesis but I found it Fascinating.

 

Which I suppose partially explains why sexual reproduction still rules the roost. Unsurprisingly, the paper linked to at the start of the thread noted that somatic variation was of greater importance to those species that reproduced by vegetative cloning and suckering.

 

There was a great picture in an old (1980s) edition of nature that had a plantation of Eucalyptus that had been defoliated by insect damage. All that remained was one branch on one tree completly un touched!!!

 

Now that I want to see!

 

There are of course other stagies that plants have evolved to allow themselves to keep one step ahead of pathogens with incredibly fast life cycles.

 

Now this is coming from the back of my memory (and is not likley to be 100% accurate) but I think there is a section on it in the Agrios plant pathology book (that I sold when I was Skint:sad:). The book talks about it in relation to the evolotion of powdery mildew on barley. Protiens that are pressent in the cell membrane recognise the powdery mildew spores and then trigger a systemic response from the plant and also programed cell death in the cells imediatly surronding the inoculation site. The powdery mildew evolves to evade these protiens. The genes that code for these protiens have high quantities of "junk" DNA except that it is not junk. The repetitive nature of the junk DNA found in genes that are responsible for resistance means that when sexual recombination occurs these genes are more likely to mutate and throw up protiens that result in resistance

 

Probably a bit rambling to understand but I tried:confused1:

 

I'm with you. thanks for the input. Lots to follow up. thanks

[Amelanchier]

if a tree can mutate its own cells with hormones, dose that count as evoloution? i always wondered with symbiotic relationships (the one where the fungi is inside the tree cells rather than around them) what dose that class as? infection or mutation. sorry if i have steped into a thread that is way out of my league but this intrests me a great deal. could any one recoment any university courses that specifically deal with genetics of trees?

 

I'll try and cover your first point below Patch. As for the second. Symbiosis would be defined as a functional relationship where both (or all!) parties benefit. Interestingly, numerous parasites have ben found that cause changes to their host to facilitate their reproduction. Those changes can be so established that to eradicate a parasite can be devastating to the local ecosystem. I suppose to confuse matters -those organisms might be parasitic on the host but symbiotic to the ecosystem!

 

Maybe this is being pedantic, but just for clarity's sake my understanding of what evolution is, is that it's the change in inherited traits from one generation to following generation via reproduction. I think what we're talking about in this thread is mutation which confers an adaptive advantage. Only one this advantage has been passed on to the next generation can it be called part of evolution. If you accept the conventional model of natural selection, then all of these mutations are totally random and it's very lucky if any adaptive advantage is achieved at all.

 

I don't personally believe in the conventional model of natural selection and favour the theories of "self-describing (autopoesis) systems" described my Capra and Marguilis is a really cool book called "The Web of Life".

 

I think that the generational concept of evolution that you refer to Scott has limits when applied to long lived species. Especially modular, generating systems such as trees. A 4000 yr old Pinus longaeva might be a different entity (genetically) than when it germinated. Does it not qualify for having adapted to its environment over time despite its individuality? Remember, that it would have let rip with an unimaginable quantity of seed in that time that was sexually mixed as well. Double whammy.

 

I dispute the notion that randomness is a weakness in what you call the 'conventional model'. Randomness is a strength. I am also familiar with the work of Margulis but see her almost total denial of genetic competition limits her view. I'm happily in the middle!!

[Will Hinchliffe]

I'd love to chase that up Phenom, if you get a chance, could you get a source???

 

Here is a section from one of the papers that our lecturer put on the web. (RU means Reiterative unit)

 

"Genomic diversity

Genomic Diversity within one crown has been shown to occur in some tree species, either tropical (9) or temperate (10), in which each RU seems to have its own variant of the specific genome, the tree thus becoming a colony of genotypes. The concept is still poorly understood; in other species, such as in Quercus, RUs' genomes appear to be homogeneous. The question is therefore, are there indeed two sorts of trees with two separate forms of genomic behaviour? The answer to this great question lies in the future of tree genetics."

 

Frances M Halle'

Francis M Halle'.doc