'adaptation' or just 'heritable deformity'
Sept 1, 2009 23:59:27 GMT -10
Post by leilani on Sept 1, 2009 23:59:27 GMT -10
Hi Lee,
Thanks for taking the time (and having the patience) to continue discussing this with me. I want to keep to the point but the following comment calls for a momentary diversion.
I have often wondered why the band areas below the peristome have received so little study. (I think such studies might be useful in understanding the developmental history of the pitcher structure.) Except for N. albomarginata few, if any, writers have had much to say about, or even note, these structures.
I think most people assume, as you (and Clarke) state, that N. albomarginata is the only species that exhibits this band beneath the peristome. However, unless I am mis-interpreting what I have seen then, these bands, although often hidden beneath the fold of the peristome, are not singular to N. albomarginata.
Below, for example, are a series of pictures of the band beneath the peristome of N. bicalcarata.
Note the “tricome” structures in the banded area .....
In the following picture you can see that many of the “tricomes” have either fallen off or been removed from the upper portion of the band.
You will notice that “tricomes” are also found in abundance outside of the banded area but this is no different from N. albomarginata.
_________________________________________
Just why N. albomarginata, in the habitat studied, catches more termites than sympatric species of Nepenthes might be attributable to a number of factors. It is noted by Clark that the species of termite most often found in the pitcher of N. albomarginata are a “surface foraging” variety which might help to explain the discrepancy between the numbers caught by N. albomarginata and N. rafflesiana. (It would be interesting to know if these large termite catches are distributed evenly among ground and aerial pitchers or if they are primarily observed to happen in the lower ground pitchers.)
Of particular interest, regarding my hypothesis: that these large catches of termites have more to do with termite behavior than with any specialized trapping strategy by N. albomarginata, is the observation of J. Moran, noted by Clark (Nepenthes of Borneo, pg. 38), that “N. rafflesiana pitchers occasionally catch large numbers of termites”.
It is noted by Clark that that “some of the Nepenthes species studied so far seem to be rather inefficient traps” and I would assume that he considers N. albomarginata to be among these. Most reports seem to show that N. albomarginata gets by on a very small catch except on those occasions when it becomes the object of obsession for an army of foraging termites. When this happens the plant reaps the benefit of the termite mob
I think it is important to consider the dynamic of these large termite catches in order for us to better determine just what is going on here.
“After opening, many pitchers observed in Brunei caught very little prey for well over three months, then, over the next couple of months, caught large numbers of termites which sometimes filled the pitchers entirely. The contents then became putrid, slowly decomposing over a period of weeks. Some pitcher which were overwhelmed by prey died, but most seemed capable of surviving the decomposition of the termites.” Nepenthes of Borneo”, Clarke (1997), pg. 38
It would seem that we might even question whether these occasional “bonanza catches” are necessarily a good deal for the plant. An extraordinary abundance of potential nitrogen for the plant but at what cost.
Termites and ants are eusocial insects and cannot rightly be considered as individuals in the same way as most species of potential prey.
“To watch a single ant apart from the rest of the colony is to see at most a huntress in the field or a small creature of ordinary demeanor digging a hole in the ground. One ant alone is a disappointment; it is really no ant at all.” Bert Holldobler and Edward O. Wilson, Journey to the Ants, pg. 107
Testing the specificity of N. albomarginata catches.
It would seem to me that the observations and experiments conducted by Merbach and others have been ill designed to determine if N. albomarginata really produce “termite specific” traps. At best, the field experiments so far conducted show that N. albomarginata catches more termites, in its natural environment, than any other creature. This is not the same as saying that “N. albomarginata pitchers specifically target these termites”. The natural environment does not provide a level playing field for this kind of quantitative catch analysis as its insect potentials are heavily slanted by the larger abundance of eusocial termites (and ants). Also, to further level the playing field we would want to eliminate the “black swan” of the “bonanza catch”. In order to prove that the pitcher of N. albomarginata are specific in their intended catch a more controlled experiment would be necessary. One possible test would involve N. albomarginata being exposed to an environment with equal numbers of multiple species of potential prey (species from their natural habitat or not) over some period of time. A post mortum analysis of the dead might then reveal some specificity of attractant or catch. Such an experiment would be free of the “bias of the mob” and the “bonanza catch”.
Thanks for taking the time (and having the patience) to continue discussing this with me. I want to keep to the point but the following comment calls for a momentary diversion.
So we have a Nepenthes that produces a structure (the trichomes) that other Nepenthes don't .... leeb
I have often wondered why the band areas below the peristome have received so little study. (I think such studies might be useful in understanding the developmental history of the pitcher structure.) Except for N. albomarginata few, if any, writers have had much to say about, or even note, these structures.
I think most people assume, as you (and Clarke) state, that N. albomarginata is the only species that exhibits this band beneath the peristome. However, unless I am mis-interpreting what I have seen then, these bands, although often hidden beneath the fold of the peristome, are not singular to N. albomarginata.
Below, for example, are a series of pictures of the band beneath the peristome of N. bicalcarata.
Note the “tricome” structures in the banded area .....
In the following picture you can see that many of the “tricomes” have either fallen off or been removed from the upper portion of the band.
You will notice that “tricomes” are also found in abundance outside of the banded area but this is no different from N. albomarginata.
_________________________________________
And furthermore no other Nepenthes in the same areas catch these termites in anything like the same numbers. leeb
Just why N. albomarginata, in the habitat studied, catches more termites than sympatric species of Nepenthes might be attributable to a number of factors. It is noted by Clark that the species of termite most often found in the pitcher of N. albomarginata are a “surface foraging” variety which might help to explain the discrepancy between the numbers caught by N. albomarginata and N. rafflesiana. (It would be interesting to know if these large termite catches are distributed evenly among ground and aerial pitchers or if they are primarily observed to happen in the lower ground pitchers.)
Of particular interest, regarding my hypothesis: that these large catches of termites have more to do with termite behavior than with any specialized trapping strategy by N. albomarginata, is the observation of J. Moran, noted by Clark (Nepenthes of Borneo, pg. 38), that “N. rafflesiana pitchers occasionally catch large numbers of termites”.
It is noted by Clark that that “some of the Nepenthes species studied so far seem to be rather inefficient traps” and I would assume that he considers N. albomarginata to be among these. Most reports seem to show that N. albomarginata gets by on a very small catch except on those occasions when it becomes the object of obsession for an army of foraging termites. When this happens the plant reaps the benefit of the termite mob
I think it is important to consider the dynamic of these large termite catches in order for us to better determine just what is going on here.
“After opening, many pitchers observed in Brunei caught very little prey for well over three months, then, over the next couple of months, caught large numbers of termites which sometimes filled the pitchers entirely. The contents then became putrid, slowly decomposing over a period of weeks. Some pitcher which were overwhelmed by prey died, but most seemed capable of surviving the decomposition of the termites.” Nepenthes of Borneo”, Clarke (1997), pg. 38
It would seem that we might even question whether these occasional “bonanza catches” are necessarily a good deal for the plant. An extraordinary abundance of potential nitrogen for the plant but at what cost.
Termites and ants are eusocial insects and cannot rightly be considered as individuals in the same way as most species of potential prey.
“To watch a single ant apart from the rest of the colony is to see at most a huntress in the field or a small creature of ordinary demeanor digging a hole in the ground. One ant alone is a disappointment; it is really no ant at all.” Bert Holldobler and Edward O. Wilson, Journey to the Ants, pg. 107
Testing the specificity of N. albomarginata catches.
It would seem to me that the observations and experiments conducted by Merbach and others have been ill designed to determine if N. albomarginata really produce “termite specific” traps. At best, the field experiments so far conducted show that N. albomarginata catches more termites, in its natural environment, than any other creature. This is not the same as saying that “N. albomarginata pitchers specifically target these termites”. The natural environment does not provide a level playing field for this kind of quantitative catch analysis as its insect potentials are heavily slanted by the larger abundance of eusocial termites (and ants). Also, to further level the playing field we would want to eliminate the “black swan” of the “bonanza catch”. In order to prove that the pitcher of N. albomarginata are specific in their intended catch a more controlled experiment would be necessary. One possible test would involve N. albomarginata being exposed to an environment with equal numbers of multiple species of potential prey (species from their natural habitat or not) over some period of time. A post mortum analysis of the dead might then reveal some specificity of attractant or catch. Such an experiment would be free of the “bias of the mob” and the “bonanza catch”.