Sundews from Queensland

[Tim Caldwell]

I was wondering if anyone knows why sundews from tropical Queensland, like schizandra, adelae and prolifera, tend to have such sparse tentacles? D. schizandra in particular often looks like it's not even carnivorous. Are there any theories about it?

[Zlatokrt]

I have read a theory, that it is because often rains - drops of water can easily flow down from leaves. I do not know, how much is it reliable. And Stewart McPherson write in his book about possibility, that these plants are evolving away from carnivory. Who knows, what is the truth?

[jimscott]

Really?

[Zlatokrt]

Really what?

But your plants are nice

[jimscott]

Thanks.... and evolving away from carnivory.

[droseraman]

Comparison between Drosera adelae and Drosera capensis leaves:

D. capensis

D. adelae (with very little light)

While D. adelae may have less tentacles, I think it traps insects just as successfully as D. capensis, which has much more tentacles (does it not?). So maybe natural selection favored Queensland dews that devoted less energy to tentacle production if it was able to catch just as many insects as it needs to thrive? Also, what is the difference in availability of insects in the tropical forest compared to

As far as evolving away from carnivory goes, I have a question-

Could a D. capensis in full sun (or partial shade from grasses) in the Cape region use more food to keep up with photosynthesis compared to a D. adelae or D. schizandra in the shade of the forest floor, which does not get as much light? (Take a look at how red some of these Capensis are when in full sun in the wild: http://ocps.proboards.com/index.cgi?board=...mp;thread=3336) Does anyone have information describing how long it takes each species to reach flowering maturity in the wild? Maybe D. schizandra doesn't need to catch as much food in the same period of time as a D. capensis before it can catch up with photosynthesis... (As of now, I have a very basic understanding of this process, so don't rip me apart please :) )

Also, when I don't let my D. adelae catch any food (and i don't feed them), they greatly shrink in size and don't flower at all. I don't think it would be advantageous to evolve away from carnivory, since few would be able to reach flowering maturity without carnivory unless the conditions were pristine.

Edited February 5, 2010 by droseraman

[Tim Caldwell]

I think D. schizandra is the most extreme example, and I could believe that it might be evolving away from carnivory. Have a look at these pics:

http://upload.wikimedia.org/wikipedia/comm..._Darwiniana.jpg

http://www.hartmeyer.de/Bilder_allgemein/D...andra_bea02.JPG

http://upload.wikimedia.org/wikipedia/comm..._schizandra.jpg

[RL7836]

The 1st & 3rd pcs in your links both appear to have wet leaves - so the dew may have been washed off. The middle one just appears unhappy at the moment (lower humidity?). Many people have difficulty growing these plants so many of the pics you find will be plants struggling to survive.

I suspect that D. schizandra's more sparse appearance may be an adaptation to it's low-light environment (fewer glands blocking photosynthetic cells). As many have noticed, this species is able to grow & be happy in lower light levels than many other (any?) CP. While the glands are spaced further apart, in a high humidity environment, they produce copious amounts of dew. When I look over at mine, I'm often amazed at how much dew they produce (check out the 2nd photo - leaf @ ~4 o'clock)

As for evolving away from carnivory ....

[Zlatokrt]

I did not thought up this theory about evolving away from carnivory myself

If i remember well, i read it in McPherson`s "Glistening carnivores..." and only as a potential possibility. On photos from nature, plants don`t have much dew. Look at this picture - http://www.redfernnaturalhistory.com/showp..._schizandra/133 - this schizandra doesn`t seem to have much dew on the leaves. There are also mentioned arthropods stealing captured pray - if they would steal too much cought insect, carnivory would cost more than the income from prey is.

When i will go back to school on monday, i will check the book and try to find, where exactly it is written.

I do not like the idea, that any of my beloved CP is trying to become non-CP (which formulation is a nonsense, the plants don`t try to become a non-CP, they are only try to survive in given conditions), but there is a certain possibility, that it is truth

On the other hand, mine schizandra has also very dewy leaves and likes to get some food, so it is certainly a CP.

Sparse tentacles could be an adaptation on high humidity and theory that it allows better photosynthesis also sounds quite realistic. And maybe it is a combination of many factors and we do not know all of them. What if there was something in the past, what let alive only population of plants with sparse tentacles, and it is gone now? Sparse tentacles could be only a remain of former evolution...

BTW: the middle schizandra doesn`t look unhappy to me - mine have never flowered yet

Adam

Edited February 6, 2010 by Zlatokrt