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Topic: Evolution of plant-insect symbiosis (Read 30555 times)
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jucce
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No it doesn't have to evolve at the same time. It could simply be an organism changing to benefit from one of its common parasites or a parasite changing to benefit its host for example. Of course, but this is unlikely for some symbiotic pairs. and, generally, the difference between a hypothetic non-symbiotic ancestor of one of the symbionts and the symbiont itself is a bit bigger than usual for a normal mutation
All it may take is adapting to utilize a new food source or a subtle change in the waste from an organism. Basically a mutation to benefit better from the environment, directly or indirectly.
And the relationships can of course be more complex, like the example with the parasite. A parasite evolving to change its waste or feed of something different/additional thereby inadvertently benefitting its host making the host more successful and therefore making the parasite (or symbiot as the relationship is now mutualism) more successful.
(also note that this can't evolve gradually). See lichens for example.
Why couldn't it be gradual? Wikipedia says:For some algae, the symbiosis may be obligatory for survival in a particular habitat; in other cases, the symbiosis might not be advantageous for the alga. Thus, there is some controversy as to whether the lichen symbiosis should be considered an example of mutualism or parasitism or commensalism. So when it comes to the lichen for example the fungus and the bacteria/algae could very well have started separately and then evolved into a parasitic or commensalist relationship and eventually to a mutually beneficial one.
Symbiosis feels very natural to me, almost like a cheeta feeding from a gaselle, a bacteria growing on fungus. Everything in nature is really connected and feeding on and off each other. So adapting mostly means adapting to benefit better from the other organisms in the eco-system around you.
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« Last Edit: April 21, 2007, 02:54:27 am by jucce »
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Arne
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I just found this, which seems to be on topic. Enjoy.
EVOLUTION OF GALL MORPHOLOGY AND HOST-PLANT RELATIONSHIPS IN
WILLOW-FEEDING SAWFLIES (HYMENOPTERA: TENTHREDINIDAE)
http://cc.oulu.fi/~tonyman/Reprints/Nyman.etal.2000.pdf
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« Last Edit: April 21, 2007, 04:48:14 pm by Arne »
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RTyp06
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Interesting link.. Learned a few things. The attacking animal is not stinging the plant but laying eggs. The produced galls offer food and shelter for the offspring. The insects often compete for the best position on the plant.
Here's an oak tree example that gives the general synopsis:
http://members.frys.com/~bpmosley/GALLS.HTM
And here's some common types:
http://www.uky.edu/Ag/Entomology/entfacts/trees/ef403.htm
The PDF paper you linked says that galling has evolved seperately many times in different species of insect. It is also believed to have evolved from leaf rollers (or more primitive processes) What I find curious about such claims is that seperate evolution of a similar process, to me, rules out random mutation. Just like the eye evolving seperately many times or the sex organs not evolving independently. If macro evolution does exist I still believe strongly that it is somewhat guided and ,for me, this sort of evolution only bolsters that belief.
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Arne
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Yeah, I was going to mention convergent evolution. It's possible that gall in this case was just the best closest solution. It's one of the sub-peaks of mount improbable where some lifeforms tend to gather. Some exobiologists use convergent evolution as an argument for the idea that some aliens might look similar to us. Maybe not funny-forehead similar, but the overall construct with limbs branching into sub-limbs, a stereo sensory limb placed high up, etc.
This is actually a problem when using genetic algoritms. Solutions tend to flock at a 'local optimum' if the population is too small or the selection method does not allow less fit solutions to sometimes reproduce aswell.
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RTyp06
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Convergent evolution is an interesting idea. But there had to be an original evolutionary ancestor in each case to deliver the novel new genetic code to offspring . To me this brings up questions.. Lots of them. We're looking at a fairly complex breeding cycle here, not a chance, happenstance process in my view.
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« Last Edit: April 24, 2007, 02:23:54 am by RTyp06 »
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Arne
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Put evolution of galls into google.
It would appear there's has been a lot of research on the subject. None of us here are gall evolution researchers (...?) and I'm not going to pretend I am. The proper channel for refuting the existing theories would probably be peer review and scientific journals. Good luck!
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jucce
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OK Arne, fair enough.. Jucce said: What do you mean exactly? Presumably the features have arisen gradually over many generations through mutations and natural selection like evolution normally progresses. What I mean exactly is that it is too contrived and essential to have accidentally been stumbled upon irregardless of how gradual the evolutionary process. Especially in light of convergent evolution where the evolutionary feature is nearly identical in many completely different species of animal. It's difficult for me to simply dismiss this as coincidence which is basicly what evolutionary biologists are doing in these cases.
I don't think they regard it as a coincident. And this hasn't been stumbled upon accidentally, the mutations are random but natural selection really isn't.
It seems like the five sense for example are very common and beneficial evolutionery functions. Any tendency for vision for example would likely be very beneficial and have much evolutionary benefit.
Like convergant evolution says, organisms will frequently evolve similar mechanisms if they fill similar niches. For example birds, insects, pterosaurs have similar wings. And the design of wings are strictly limited by aerodynamic principles, one might even say that there's a perfect wing design that evolution will strive towards.
Sure the mutations are random, but natural selection is not.
Natural selection is random. It is an undirected process. An amimal may evolve bigger teeth but without the legs to chase down it's prey, they're useless. And if it did evolve longer legs so what if it's heart is too weak to utilize them. And none of this would matter without sensory organs and a brain to detect prey in the first place.
Natural selection is a non-random cumulative process. If an animal developes something that's neutral or detrimental it probably won't be passed on to future generations.
So to stay on topic, how can natural selection gradually fine tune the gall producing insects life cycle to what it is today? Think about how many things had to go just right to make it possible. And not only once but within many species. Just evolving the tools to break the plant skin and deposit it's eggs is improbable across multiple species let alone the larve having the nessicary tools to break out of it's cocoon.
Well like I said, natural selection is a gradual, cumulative and non-random process. Sure the end result is complicated, but it's not like it was formed from nothing instantly, the change was gradual, cumulative and over very long timespans. Gradual change can and do result in very complicated results.
Someone described it as opposed to drawing lottery numbers until you hit the exact ones you have, instead draw the numbers but keep the ones that fit. That way you'll reach your own improbably numbers much faster.
Yes here it was:
http://www.youtube.com/watch?v=EDFJviGQth4
That user has other interesting videos too:
http://www.youtube.com/profile_videos?user=cdk007
Nearly every aspect of life from DNA itself on up is just too contrived to attribute to random chance, and esentailly that is where all new novel genetic code comes from according to evolutionary scientists.
Yes the mutations themselves are random, but like I said natural selection is not.
And there are also other things than random genetic mutations that may contribute to much change in the genetic code. Hybridisation, gene flow, genetic drift and even symbiosis etc.
And other interesting ideas:
http://www.cambridge.org/uk/catalogue/catalogue.asp?isbn=0521317932
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cm....;amp;query_hl=2
http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?cm....3935&query_hl=4
Here's a text about how it may be intuitively difficult to see that so much arose through random genetic mutations selected over time. And they use the "antibody response" as an example.
http://www.talkorigins.org/faqs/fitness/
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« Last Edit: April 25, 2007, 03:04:56 pm by jucce »
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Baltar
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In a way his arguments are quite clever.
The fact that RType06 survives is evidence that natural selection does not work at all. So RType wins. QED.
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Valaggar
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The fact that RType06 survives is evidence that natural selection does not work at all. While this IS a clever insinuation, it is not an appropriate one.
Also, nobody says that NATURAL SELECTION does not exist - the thing that is argued about is whether it can produce new species or not.
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Lukipela
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Also, nobody says that NATURAL SELECTION does not exist - the thing that is argued about is whether it can produce new species or not.
Indeed. One side claims that natural selection can only allow animals to adapt, but not to change. Others claim that adaption under a sufficiently long period gives rise to new species.
Uhhh yes, it really is random. Think about it man, natural selection covers things like mass extinction. A plauge or meteor is a random event. Local phenomena. Local preadators.
Mass extinctions are part of natural selection just like everything else. It is simply rearranging the rules. Look at the dinousaur. First, natural selection fgavours huge big giants because vegetation and climate is favourable. After the meteorstrike, the rules change, and dinosaurs no longer have an advantage. There is no logical progress behind natural selection, but it isn't a random process. Those best adapted to the current enviroment whatever that might be, do well.
Isn't it random that a powerful predator will exist in any given area?
Wouldn't it be weirder to have no powerful predators? Assuming that natural selection favours those individual in a population that are best at getting sustenance and reproducing, predators are quite logical. And assuming Panagaea existed, what is now local might not always have been. It would seem more questionable from a ID standpoint, if everything is part of a plan, why place large and different predators everywhere? Why not just have one ur-predator that then adapts to local circumstances through natural selection but is still of the same species?
Biological features themseleves only benifit a species if the environment is just right. etc. etc. There are so many variables we cannot even begin to fathom them all. Just because an animal is prolific is no guarantee of survival..
Very true. Thus only biological features that are beneficial (or at the very least non-harmful) are preserved. That is natural selection. Just because there are many variables doesn't mean something is impossible. It's impossible to accurately simulate a fluid-bed reactor
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What's up doc?
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