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Topic: Evolution of plant-insect symbiosis (Read 30602 times)
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Deus Siddis
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If plants or mulitcellular euglenoids or something wanted to branch out into the territory of another kingdom, they would have to compete with already established symbiotic organism pairs in which one of the two has photosynthesis capabilities, like lichens or a lettuce leaf nudibranch.
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Death 999
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Opening them up there are small insects inside. if the insects are indeed injecting DNA to build a home as you say, how would you suspect somthing like this evolves without any sort of planning or foresight? (Not trying to derail, just one question) Well, let's see what ingredients you need:
1) a venom-injecting insect whose venom dissolves cell membranes
1a) its defense against its own poison is not perfect
2) it builds this sort of cocoon around itself normally.
step 1: the insect, building its cocoon on a handy tree, stabs the tree to hold on. This injects some of the venom
step 1a: note that this venom has bits of the insect cells in it, due to ingredient 1a, above.
probability: likely
step 2: the venom dissolves some tree cells. At some radius from the injection point, the cells are weakened but not destroyed.
probability: certainty
step 3: DNA from the venom fluid (which, as noted above, contains insect cell fragments) diffuses into the affected tree cells.
probability: kind of unlikely in any one case
step 4: the tree tries to heal up, and the affected cells (those first cells to survive the attack) are those who do most of the reproducing to replace the destroyed cells. This happens to spread the insect DNA.
probability: near certainty
step 5: the insect has been spreading the signalling proteins to turn on its 'cocoon' genes; some of these diffuse out into the tree, activate those genes
probability: depends. Could be very likely.
step 6: the infected tree cells help make the cocoon
probability: follows from the earlier steps
and there you go. Unlikely but possible to happen by accident. Leaves lots of room for gradual improvement.
By the way, you were asking for a 'just-so story', right? Cause that's all I've got, not having looked at the situation.
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« Last Edit: April 18, 2007, 04:36:43 pm by Death 999 »
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Valaggar
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This is not something that transmits genetically, and insects aren't capable of learning. Ergo, this would remain an accident and nothing more, not a species trait. No way to evolve this one (as, generally, other learning-needing traits on more "primitive" species).
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Death 999
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The ability to make this happen can be transmitted genetically.
What else could I possibly mean? The actual event itself is transmitted genetically? That makes about as much sense as the idea that having a peanut butter and jelly sandwich for lunch is transmitted genetically.
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Valaggar
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You know, in order for this to be transmitted genetically there must be a gene for it. And the gene surely won't appear out of nowhere if, by accident, such a cocoon is formed.
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Death 999
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Let's split this off...
Moderator? If I make a new thread, can the relevant posts of this thread be prepended to it?
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Death 999
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Muchas gracias.
Valaggar, did you notice that both of these 'ingredients' that I pointed out would be necessary would be things that would be genetically encoded, and moreover would be able to vary in a nearly continuous fashion towards making this process more reliable?
It doesn't have to be one gene; it can be, and usually is, a suite of genes.
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Valaggar
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Apropos, my last report said report said that meep-eep is Scottish... err, Dutch, not Spanish.
Ah, I hadn't noticed. Anyway, the evolution of all sorts of symbiosis (especially mutualism) is unlikely - both sides must evolve cooperation at the same time, which is practically impossible.
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RTyp06
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I wonder if Arne's example is "symbiosis" because I'm not seeing the benefit to the plant itself. i do question as to why would an insect sting a plant leaf in the first place, let alone inject DNA that forms a cocoon.
A better example of animal/plant symbiosis might be somthing like orchids that mimic female wasp colors and pheremones to attract a specific sort of wasp to pollinate it. The wasp benefits by collecting pollen for food although he doesn't get to breed.
Seems most true symbiosis between animals and plants take place in the sea.
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Valaggar
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Symbiosis is not necessarily mutualism. It may be commensalism, amensalism, neutralism, parasitism or even competition.
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Draxas
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However, it's general good practice to use symbiosis only when discussing mutualism, and the other terms when discussing them specifically. It halps keep your point clearer.
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Valaggar
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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 (also note that this can't evolve gradually). See lichens for example.
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