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Skipjack Joe
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At the risk of sounding to preachy I'll write what I think:
Two species involved in a symbiotic relationship have evolved to a degree where they interact with one another. That means that one or both seeks the
other out to perform this interaction. This is done by individuals as genetically programmed at the species level.
One straightforward way to determine whether symbiosis is occuring is by measuring the distribution of individuals relative to themselves and relative
to the other species.
If all the individuals are equally distributed in an area there is antagonistic relationship between individuals. Lobsters are like that as they are
territorial.
If the individuals are totally randomly distributed there is likely no interaction between the members.
If, however, one or both species have a clumped distribution and it's clumped around the other species you probably have some kind of interaction
between the two (even though you don't know what it is).
So the question is were the cacti clumped around the trees, or the trees clumped near cacti, or both? Or was there just a set of plants, with some
being in contact with one another and some not? If the latter, were the clumped individuals statistically significant from the non-clumped ones? One
needs to plot an area out, count them out, and do the stats.
But from where my travels have taken me I have seen miles of cactus without adjoining trees and have seen lots of arroyos with trees with a few cacti
in their midst. So that's why I don't think real symbiosis is taking place. Another words, no species is actively 'seeking' the other. In plants,
'actively seeking' are seeds more sucessfully germinating next to the other species than elsewhere. One of the two species should at least be doing
that in a symbiotic relationship to my way of thinking.
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Mexitron
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Yes, I think that's about right Skipjack...the "nurse plant" situation is more of an opportunistic luck of the draw than a real symbiosis...
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DianaT
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| Quote: | Originally posted by Mexitron
yup, the "flowering" cactus has a condition known as "cresting" and it is generally caused by a virus getting into the apical cells where cell
division starts.
its an interesting idea---that the mesquite and the cactii have a symbiotic relationship...although from what I know of, the symbiosis is mostly in
favor of the cactus...very often you will find that cacti seedlings growing in the shade of a mesquite or other plant---in these cases where the host
plant is protecting the seedlings from full sun the host plant is called a "nurse plant". But a symbiosis would imply a benefit to the mesquite which
I'm not sure there is.
Another twist though is that cacti are actually descendents of tropical vines---they evolved out of the tropics as deserts were forming millions of
years ago---in fact there are a few intermedaries still growing today--one example is Pereskia and it looks like a vining sprawling cactus...!
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Really interesting information. Being one with VERY limited scientific background, I really appreciate the scientific information.
Curious if this is an example of cresting you talk about. This one interested me as it looks like two different things growing? Ignore the
carving---I need to clone that out.
Thanks, and I really want to go to that place! Nena, I bet you have more pix of that place hiding on your computer.
Diane
Just read Skipjack's post---thanks, your description and definitions are interesting.
[Edited on 3-6-2010 by DianaT]
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Natalie Ann
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Thanks you much, Mexitron, for clearing that up about the symbiosis. I do understand now that a nurse plant does not imply symbiosis in and of
itself. Also, I'd heard that roses are descendants of cactus... now I understand cactus evolved from tropical vines. Mother nature never fails to
amaze me.
Igor - In this area which has been sanctuary for some good long time, the cactus and trees are so thickly intertwined that it's difficult to say which
came first - the chicken or the egg. You should visit the place when you're down this summer, have a look for yourself.
Diane... The 'crested' cactus image is the one you said you wanted.
nena
Be yourself, everyone else is already taken.
.....Oscar Wilde
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DianaT
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| Quote: | Originally posted by Natalie Ann
Diane... The 'crested' cactus image is the one you said you wanted.
nena |
Thanks----now I can name "my" newly acquired photo. 
Makes since to me now ---just a little slow on the draw.
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Mexitron
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Diana---that looks like an actual flower-- it looks like the old flower base is resting towards the bottom of the orange stuff...I'm not sure but it
might be a flower that fell onto that branch from higher up...???
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Mexitron
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here's a cresting cactus:
http://t0.gstatic.com/images?q=tbn:foGwwE-YOAu40M:http://ima...
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DianaT
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| Quote: | Originally posted by Mexitron
Diana---that looks like an actual flower-- it looks like the old flower base is resting towards the bottom of the orange stuff...I'm not sure but it
might be a flower that fell onto that branch from higher up...??? |
Thanks---it looked like it was growing because I did not get that close---I love cacti, but I have not had good experiences touching them. But I enlarged the picture and it does look like it is just resting.
Maybe the big storm knocked it off.
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BajaBlanca
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Your pictures are really beautiful ... and we weill surely visit the cactus sanctuary, now that we know it exists !
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ecomujeres
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| Quote: | Originally posted by DianaT
Curious if this is an example of cresting you talk about. This one interested me as it looks like two different things growing? Ignore the
carving---I need to clone that out.
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The photo you show here is a cardon that has had a stem or branch cut off and then it has healed over the wound. The little yellow balls are just the
remains of the cardon fruit sitting on top of the cut stem.
As Mexitron said, I too learned that the cresting was caused by a virus that hijacks the plants DNA and ends up causing this typical growth pattern.
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ecomujeres
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Oh, and the longer tubular thing on the bottom left of the balls is probably part of the fruit's outer layer after it lost the ball-like clusters of
spines.
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ecomujeres
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A couple of comments about the original photos of intertwining cacti and mesquite as well as the sprouting cacti in the crevices.
I would hazard to say that the tree was likely there first. As the cactus (Pachycereus pectin-aborigenum, or Cardón barbón) grew, where the tree was
pressing against its tissues, it grew to envelope the tree's branches.
If you've ever seen a Cardón that has been vandalized, meaning something jammed into it, or wrapped around it, the tissues can eventually grow to
envelope the object. Trees do this too. The result is that it looks like one or both are growing out of the other.
Next, the cactus seedlings are taking advantage of the accumulated dirt in the angle of the branches. Think of epiphytes like bromeliads and orchids
that grow in trees, clinging to the trees but not getting any benefit other than a place to live. Their roots don't penetrate the base plant's bark
nor do they steal nutrients from the base plant. These micro-environments catch and hold nutrients and water for the seedling's growth.
It would be interesting to see how large these plants could become as they begin to require more nutrients than their house can provide.
I can't wait to go back to El Santuario. It's well worth the trip.
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