The venus Fly Trap

[Severian]

How did the Venus Fly Trap evolve? There seem to me to be some organisms which have features that are difficult to come by through evolution, and the Venus Fly Trap seems particularly difficult to explain.

 

To catch a fly, it needs to have 3 properties:

 

1. Attract the fly. This is presumably quite easy. All it needs to do is be a rotten flesh colour (and perhaps smell - do VFT's smell?) and flys will come. However this property has to be developed in conjunction with the other properties, otherwise there is no advantage to the plant in attracting flies. This is the same problem that flowers face in attracting bees (ie there has to be something for the bees to do). In that case, the pollen was possibly just being blown in the wind without the bees, and so the precence of bees helped carry it further. This can't work for the VFT since there seems to be no gain to the VFT unless it can digest the fly, so we need some other mechanism.

 

2. Trap the fly. To me this seems the hardest to evolve. The VFT has to sense the presence of the fly and close very quickly to trap it. The problem here is that it is all or nothing. If the fly escapes, nothing is gained. So we can't evolve a 'half-way-house' mechanism where the trap shuts more slowly. On the other hand it seems too big an evolutionary jump to move to a fast closing mechanism in one step!

 

3. Digest the fly. There is no point in trapping the fly if the VFT doesn't digest it. However, there is no point in trapping it if it isn't going to digest it. So it seems as if this would have to evolve simultaneously with property 2.

 

 

The main problem here seems to be that it seems unlikely to evolve all of these properties at once, but all three are needed for an evolutionary advantage. So I suspect that they didn not all evolve at once, and there was some other advantage to be had for each one, perhaps by having some other complimentary mechanism already in place which was later lost.

 

For example, there are other types of plant that eat flys, which catch the fly in some sort of liquid or sticky glue. There is a goblet like flower with sticky liquid in it, and why a fly comes to investigate, it gets stuck and is digested. There is no problem with this evolving because the plant could still photosynthesis normally, not using the dead flys it traps, until one day it's offspring mutates into something which absorbes the nutrients from the liquid. (It is not clear to me how the glue evolves, but presumably it had some other evolutionary use.)

 

Could a similar mechanism have evolved the venus fly trap? For example, a fly might be able to crawl out of the liquid given enough time, so a flower which closes (a chance mutation) could be more efficient. Then closing faster and faster would help the plant, eventually evolving into a VFT.

 

Does anyone know the 'official' explanation of how the VFT evolved?

 

 

The few links I could dig up, aren't very helpful:

http://www.strato.net/~crvny/sa03005.html

http://www.talkdesign.org/faqs/icdmyst/ICDmyst.html

 

The last one seems to support the proposal that there was a sticky substance which was lost. But why would a VFT without the sticky 'glue' be more efficient than the one with the glue?

 

(Disclaimer: this post is not intended to disprove evolution or in any way imply that evolution is not the correct theory for the origin of species. It is simply a non-expert asking a (presumably dumb) question about something he would like to know more about. (So that I have a good answer when arguing with creationists!))

[Newtonian]

Despite the fact some posters here would have us believe that we know all there is to know about evolution.In all honesty we actually know very little.

We can observe that it happens,and have amassed great quantities of circumstancial evidence.The geological column and phylogenetic analysis overwhelmingly point to evolution.But its many mechanisms are still beyond our comprehension.However you dont need to know the mechanism for an occurrence, to accept an occurrence.If that makes sense.(one supposes your frustration with gravity)

 

Anyway there are approx 5-600 species of carnivorous plants(approx because there are many many species of plant/animal yet to be found/recorded.A case of too many species too few taxonomists.

Regarding the VFT unfortunately we just dont know how it evolved(well no substancial evidence we can cite that would satisfy a panel of physicists).Carnivorous plants tend to be soft bodied so presently no fossils im afraid(well we have but not relevant here)!!

But it is only a plant and survives by photosynthesis.They live in nutrient poor soil and the insects are an extra source of nitrogen supplement(please dont ask what your thinking)

 

At present the discussions on evolution/ID dont merit any significant input from myself.I just thought you should be informed before the looney's reply

[[Tycho?]]

It could have evolved such that it trapped some species of insects, while allowing others to escape. This would keep the mutation in the gene pool and allow it to develop the genes to digest the fly.

 

This is just speculation of course.

[rakuenso]

god did it

[iglak]

why do they all need to evolve at once?

 

it could be that the ancestor already had the ability to digest insects in it genes already, even before it was needed.

 

it could be that the original venus fly traps migrated into or lived in an area with more bugs than any amount of plants or animals could deal with, and happened to have a sticky flower, or a flower that closed slowly with changing air pressure, temperature, or light levels. this would catch a bug every once in a while, and would negate the need to attract the bugs until more predators moved in.

 

it could also be that the soil wasn't very devoid of nutrients, but collecting the extra nutrients from a few bugs allowed it to grow slightly larger than the others, or slightly faster, slowing the growth of he others.

[PhDP]

It's an interesting species, and the speculation about it's evolution is also interesting, but I think an honest answer would be; we don't know exactly. I don't think we'll ever be able to understand the exact evolution of all organisms.

[Deathby]

I don't know, but here's a guess.

 

Property 1 evolved first. Plants already need to attract insects to pollinate themselves, not too tricky. A plant evolved with some funky smell (I assume a single gene could produce this so its not too great a co-icidence) and flies were attracted. I believe other plants are pollinated by flies and could have been adapted by the VFT. But I don't know if it evolved from pollinating plants.

 

The second part is most difficult, considering we don't know how it works. I remember reading something recently in New Scientist about high speed cameras capturing it switching from concave to convex (or the other way around) as soon as it felt movement.

 

However, it jsut occured to me that we are assuming the VFT is the first carniverous plant. What about the honeydew (I forget the name) which is just a little bowl of sap which the fly falls into and gets stuck in? That would reasonably solve the top 2 problems. Plants often have sticky, tasty stuff to attract insects, it wouldn't be too difficult to adapt that to catch the insect instead. I don't know about point 3, my knowledge of enzymes is mostly restricted to "they help activation energy" but is it possible that they already had enzymes to squeeze as much nitrogen out of the soil as possible, then simply used those on insects?

[zyncod]

Venus flytrap is a member of the sundew family - all these (carnivorous) plants have tenticles on their leaves that secrete a gluelike substance. Insects get trapped and then digested. So imagine that a sundew evolved the ability to close one of their leaves on their prey (let's say that moving one of the tentacles caused a thigmotropism-like reaction). It wouldn't need to close the leaf lightning-quick because the insect was already stuck. But it would provide a selective advantage in that the insect couldn't really struggle away any more once the leaf was closed. And evolution provided for a quicker and quicker mechanism until the flytrap no longer needed to use the glue to capture the organism but could simply clap shut on the insect.

 

As far as point 3 goes, I'm not sure what the ancestors of sundews are, but if you looked it up, you could probably imagine a fairly convincing mechanism for how the glue/digestive capabilities evolved (perhaps the leaves' tentacles were used to secure the plants to surfaces, like ivy, and the plant may have evolved the capacity to digest insects that kept getting stuck on their leaves anyway - probably not right, but just a thought).

[Daecon]

Just imagine what they would have been like if they existed in the precambrian period.

 

It'd be like the Little Shop of Horrors.

 

I love Venus Fly Traps, I've had two at different times before, and they both grew stems of white flowers, that reminded me of a miniature hyacinth. It's cos they loved me back.

[slur]

Evolutionary conundrums like the Venus Fly Trap fascinate me the most. But a VFT is orders of magnitude simpler than a spider, so I imagine the answers are a bit simpler to deduce. There are several things I try to remind myself when approaching such a puzzle:

 

1. Those that can win over those that can't.

 

2. Mundane features get readapted to new uses.

 

3. Evolution doesn't happen in a vacuum. Organisms co-evolve systematically. Or, ecosystems evolve as a whole. In the long run, organisms that fit tend to win over those that predominate.

 

4. Selection gains momentum: static features of organisms reflect and encourage developmental tendencies. To put it another way, the process of evolution doesn't just evolve forms but also evolves mechanisms that accelerate and improve evolution itself. Those organisms which adapt more quickly and more appropriately across successive generations are favored over those which mutate more slowly and in a more random manner (up to a point - it's a balance).

 

So let's get down with the Fly Trap puzzle!

 

There is nothing novel about plants being able to absorb nutrients, so it's just a matter of root capabilities drifting into leaf capabilities. There's nothing novel about the production of nectar, and there's nothing novel about plants producing all manner of caustic substances. All these elements got readapted in the VFT.

 

I would draw history this way for precursors of the VFT:

 

- Precursors with stickier leaves caught more flies and so ended up with more nutrient-rich soil once trapped insects decayed.

 

- Precursors with bowl-shaped leaves trapped more insects.

 

- Precursors that accelerated the decay of insects won over those that didn't, so leaves with more caustic digestive chemicals were selected over leaves with less caustic digestive chemicals.

 

- Leaves that closed reduced the amount of digestive enzyme required, thus saving even more energy for the plant.

 

- Precursors that used less energy in the production of sticky nectar were more energy-efficient and thus could produce a greater number of viable seeds.

 

- Leaves which lay open a certain amount were selected over those which were folded a certain amount... sometimes. Dependent on their shape.

 

- Leaves which folded in response to touch were selected overall, in a very gradual manner, because openness and folded-ness both brought competing advantages. Eventually, the quick-snapping trap-leaf was "hit upon." (It is likely that precursors had varied leaf types, and even increased variation within the same plant for many generations.)

 

- Leaves with interlaced spikes were selected over leaves with no spikes, or spikes that didn't interlace.

 

The specific order of these developments is certainly wrong, but without a doubt all these sorts of selections had to have occurred to give us the modern Flytrap.