16 replies to this topic

[Vic2]

I heard recently from a highly reliable source in Norfolk - no, not Norfolk, Virginia - that B. tatei is now classed as a carnivore.

Intrigued, I did a spot of research:

Most sources say don't mention B. tatei among the carnivorous bromeliads, but several sources still list it as a possible carnivore (e.g. 1, 2).

Wikipedia states that "one terrestrial population of B. tatei was discovered with heterocystous cyanobacteria in its tanks, suggesting N fixation." But the presence of bacteria could also suggest a digestive capability, as in Heliamphora?

Does anyone have an authoritative answer?

Interested of Letchworth  :)

[Dave Evans]

Vic2, on 23rd August 2010 - 17:32 PM, said:

I heard recently from a highly reliable source in Norfolk - no, not Norfolk, Virginia - that B. tatei is now classed as a carnivore.

Intrigued, I did a spot of research:

Most sources say don't mention B. tatei among the carnivorous bromeliads, but several sources still list it as a possible carnivore (e.g. 1, 2).

Wikipedia states that "one terrestrial population of B. tatei was discovered with heterocystous cyanobacteria in its tanks, suggesting N fixation." But the presence of bacteria could also suggest a digestive capability, as in Heliamphora?

Does anyone have an authoritative answer?

Interested of Letchworth  :)

AFAIK, all Sarraceniae produce digestive emzynes, just the research has been a bit spotty...  I don't believe any of them rely exclusively on bacteria for digestion, but rather manage the colonies of bacteria for better digestion and to limit the chance the prey rots and in turn rots the leaves.

So where is the line dividing plants that farm bacteria, and those which are carnivorous?  Seems like there is now a tread toward declaring all plants which farm bacteria as carnivorous...  Seems similar to painting stripes on a house cat and calling it a tiger...

Edited by Dave Evans, 01 October 2010 - 23:18 PM.

[Vic2]

Dave Evans, on 1st October 2010 - 23:17 PM, said:

So where is the line dividing plants that farm bacteria, and those which are carnivorous?  Seems like there is now a tread toward declaring all plants which farm bacteria as carnivorous...  Seems similar to painting stripes on a house cat and calling it a tiger...

This might help:

"Distinct species are not a fact of nature, but of language ... There are, it is true, differing things in nature, but the differences proceed by continuous graduations: 'the boundaries of the species, whereby men sort them, are made by men'."    Bertrand Russell (1946) in History of Western Philosophy.

Farming bacteria is just a step on Darwin's sand walk to carnivory.
It's just people who feel the need to draw a line in the sand, and give each side of the line a name.

Vic

[Dave Evans]

Vic2, on 2nd October 2010 - 06:12 AM, said:

Farming bacteria is just a step on Darwin's sand walk to carnivory.

No, not really.  Please read:

http://icps.proboard...amp;thread=4100

[RL7836]

Vic2, on 2nd October 2010 - 07:12 AM, said:

It's just people who feel the need to draw a line in the sand, and give each side of the line a name.

... but wasn't your request for a definitive status update on which side of this fabricated line B. tatei currently resides?

[Vic2]

RL7836, on 6th October 2010 - 14:59 PM, said:

... but wasn't your request for a definitive status update on which side of this fabricated line B. tatei currently resides?

Er... yes, and no!    

It wasn't the woolly 'fabricated line' about species divisions, but the clearer and more easily defined, all-or-none 'fabricated line' about carnivory.
'Does it eat on purpose, or does it not?', rather than 'Are these two plants different enough to be different species'?

I guess I should have been more specific in my question (rather like 'Deep Thought' in The Hitchhiker's Guide to the Galaxy):

What I really wanted to know whether B. tatei was known to deliberately eat anything, or just did so by chance.
E.g. Does it secrete phosphatases and proteases into the tank fluid, intentionally absorb nutrients from tank fluid which are derived from victims, make any deliberate effort to cultivate bacteria which can digest victims in tank fluid , etc.

I believe that deliberate production of enzymes involved in digestion has been demonstrated for B. reducta and B. hectioides.

Any info, anyone?

Interested of Letchworth  

Edited by Vic2, 07 October 2010 - 10:01 AM.

[Vic2]

Dave Evans, on 5th October 2010 - 23:41 PM, said:

No, not really.  Please read:

http://icps.proboard...amp;thread=4100

Hate to disagree, but deliberately encouraging digestive bacteria (symbiosis?) does seem to be a clear step towards having its own digestive processes. A step on the road to more specialised forms of carnivory.

Vic

P.S.
I read your topic. Interesting.
But more concerned with speciation than the development of carnivory?

Edited by Vic2, 07 October 2010 - 10:25 AM.

[LeeBr]

Hi Vic2,

sorry to come to this topic late but I only just noticed it and no one seems to have given you a definitive answer.
Givnish, Sytsma et. al.'s paper on Brocchinia which is referenced in the wikipedia article on Brocchinia seems to be the definitive work on their ecology and systematics, even though it is from a while ago (1997).
Parts of it are available on Google Books although unfortunately not the part discussing the ecology of B. tatei.

One B. tatei population was found with cyanobacteria forming plugs in the centre of the plants; these are nitrogen fixers and it was suggested that this was a symbiotic association.

These cyanobacteria are unrelated to the types of bacteria which aid digestion in some carnivorous plants.

None of the B. tatei populations studied were found to be carnivorous, but B. tatei was in a clade with B. reducta and B. hechtioides and was suggested to have possibly lost the carnivorous habit which the ancestor of all three species may have had.

So the short answer seems to be that B. tatei is not carnivorous.

However it is possible that more recent studies may have refuted this conclusion but I have not seen any.

Perhaps Stewart MacPherson may know something about this.

Or you could try emailing Givnish or Sytsma and asking them; scientists are often happy to discuss their work with people who are interested in it.

In any case their paper is definitely worth reading if you can get it; even the partial bit on Google Books is worth looking at.

LeeB.

Edited by LeeBr, 17 October 2010 - 22:23 PM.

[Vic2]

Many thanks, Lee!  

I recall that cyanobacteria are toxic, too. Which would make the rosette tank fluid toxic...   Hmmm... Probably just coincidence, till proven otherwise!  

When I get a round tuit*, I'll give the authors a mail.

Cheers,

Vic

*"Around to it";
A very old (and very bad) joke, which should remain in the Northern Hemisphere, where it belongs!  

Edited by Vic2, 18 October 2010 - 08:39 AM.

[Amar]

here you go, matey.

http://img.geocachin...425a2df2766.jpg

[Vic2]

Amar, on 18th October 2010 - 08:56 AM, said:

here you go, matey.

http://img.geocachin...425a2df2766.jpg

Trust you to have one, Amar...!!!  

I'm putting it on my machine screen as the Wallpaper.

Cheers,

Another Northern Hemisphere Joker  

[Dave Evans]

Vic2, on 6th October 2010 - 18:37 PM, said:

Hate to disagree, but deliberately encouraging digestive bacteria (symbiosis?) does seem to be a clear step towards having its own digestive processes. A step on the road to more specialized forms of carnivory.

I agree with that too, but I'm not sure that using nutrients freed by bacteria makes a plant a carnivore.  All plants use nutrients that were made available to them by bacteria and fungi digesting something.  Killing and eating make a carnivore.  If the plant is trapping (killing) prey and using bacteria for digestion it is a carnivore.  Killing without digestion and direct absorption of nutrients via the leaves (eating), then it is a non-carnivore.

[Vic2]

Dave Evans, on 3rd November 2010 - 21:02 PM, said:

I agree with that too, but ...  Killing and eating make a carnivore.  If the plant is trapping (killing) prey and using bacteria for digestion it is a carnivore.  Killing without digestion and direct absorption of nutrients via the leaves (eating), then it is a non-carnivore.

Good point, Dave...
Deliberate killing and eating define a carnivore.

But I'd suggest that deliberate killing and passive absorption of nutrients is still a carnivore.
Deliberate killing and no absorption of nutrients is a non-carnivore: It's just a method of plant defence against predation.
E.g. the trichomes on the leaves of wild potatoes, which trap aphids, Colorado beetles, etc. wandering over the leaf. (Refs 1, 2). Contact with two types of these hairs, and some incredible specialised chemistry, is needed to coat the attacking insect with a layer of phenolic resin (similar to the black, plastic-like 'Bakelite' once used as handles for frying pans) and kill it. There's no evidence that the potato plant can absorb anything from the icky goo that results; it's not like Drosera mucilage, but something like the visco-elastic polymer produced by Roridula. And it's unlikely that Roridula gets any nutrients directly from its polymer-trapped prey, otherwise why would it need Pameridea...

Either way, on the evidence - no loose wax, no honey smell, no digestive enzymes or bacteria, unlike other members of Brocchinia - it's unlikely that B. tatei deliberately kills and eats anything, so I'm more than happy to accept Lee's interpretation that the plant is non-carnivorous.

What do you guys think?  


Vic

[johns]

Vic2, on 4th November 2010 - 14:10 PM, said:

Good point, Dave...
Deliberate killing and eating define a carnivore.

I think the word deliberate may be a bit off, considering that we're talking about plants. From the perspective of evolution and of the plants themselves, mechanisms for trapping and digesting result in increased fitness (i.e. more resources to spend on growth and reproduction), but at no stage are the plants or the evolutionary process that produce them aware that they're killing animals, just as the plants are not aware that producing beautiful flowers attract pollinators.

[Vic2]

johns, on 4th November 2010 - 14:56 PM, said:

I think the word deliberate may be a bit off, considering that we're talking about plants. From the perspective of evolution and of the plants themselves, mechanisms for trapping and digesting result in increased fitness (i.e. more resources to spend on growth and reproduction), but at no stage are the plants or the evolutionary process that produce them aware that they're killing animals, just as the plants are not aware that producing beautiful flowers attract pollinators.

I think you mean 'deliberate' in the sense of 'deliberation', involving conscious thought.
Perish the thought!! (and please excuse the pun...)  

I was using 'deliberate' in the sense of 'purposeful'. (The antonym in this case would be 'accidental').
A carnivorous plant isn't trapping insects by accident.

Vic

[agustin franco]

Hi all:

Even the word "purposeful" is misused in this context. there is no purpose as opposed to function.  Purpose, again is mediated by rational thinking.
Function, on the other hand, is what most biological structures have. If they don't have it, they lose it. ie, limbs in lizards as opposed to no limbs in snakes.

Gus

[Vic2]

agustin franco, on 19th December 2010 - 00:59 AM, said:

Hi all:

Even the word "purposeful" is misused in this context. there is no purpose as opposed to function.  Purpose, again is mediated by rational thinking.
Function, on the other hand, is what most biological structures have. If they don't have it, they lose it. ie, limbs in lizards as opposed to no limbs in snakes.

Gus

This has moved an awfully long way from the thread subject...  

I think you've misunderstood "purposeful", Gus.   It by no means has to imply rational thought.
To descend into semantics - with many apologies to those who aren't this sad - 'purposeful'  can mean 'to fulfil a purpose'.  And 'purpose' - a polysemous word - can mean 'function'! See this dictionary definition.

Now, guess which  meaning I meant?  

I hope this is the end of this nitpicking, 'cos it  was fun to start with, but even I am getting bored with it.     

Current consensus is that Brocchinia tatei isn't carnivorous. 'Nuff said.

Merry Xmas to Gus and everybody,

Vic