Re: sub carnivores

From: Charles Clarke (clarke@hkstar.com)
Date: Wed Nov 04 1998 - 21:24:34 PST


Date: Thu, 5 Nov 1998 13:24:34 +0800 (HKT)
From: clarke@hkstar.com (Charles Clarke)
To: cp@opus.hpl.hp.com
Message-Id: <aabcdefg3514$foo@default>
Subject: Re: sub carnivores

Dear Jan and other sub-CPer's,

Sorry to set the cat among the pigeons and then disappear for several days!
Fernando is staying with us at present and we have just had a very nice day
checking out D. oblanceolata here in HK. Work is hectic and I still owe a
lot of other people e-mails. Many apologies if you are one of them!

The sub-CP debate that has been taking place since my message was posted is
far removed from the subject of the original complaint I made. I am not
trying to foment a revolution or overturn Jan's definition of a CP! All I
am asking for is some recognition by Jan (and perhaps others) of the fact
that alternative opinions exist and are yet to be rejected by the
scientific community. Anybody who thinks I am trying to do anything else
missed the point of my message (presumably).

Now, moving on to Jan's reply to my message...

>Including too many elements in a class is at least as detrimental to
>the concept as including too few. Admitting that we are discussing
>points or areas on a gray scale does not mean that there are no
>differences. The great advantage of the (oversimplifying) endogenous-
>enzyme criterion is the identification of a core group that is pretty
>on the black side of the scale.

I have no disagreement with that - your logic is fine on all counts. I
haven't responded to several other paragraphs in your reply, as I have no
disagreement with them either.

>I think even you or your fellow ecologists will admit that the
>bromeliads, _Roridula_, or even _Byblis_ are somewhat less
>consistently carnivorous than an "ordinary" CP like _Drosera
>rotundifolia_, irrespective of the amounts of prey trapped.

I don't think I would ever refer to any plant as being "less consistently
carnivorous" than another in this sense, except when referring to those
species which are carnivorous at some time during their lives, but not at
others (e.g. T. peltataum). Otherwise, the implication is simply that some
of them eat less meat than others!

>This is not quite true. First, there is an introductory text
>explaining roughly what is regarded a CP and what is not in the
>database.

Yes - this is a fair point and if my message suggested that I was not happy
with this, then it was poorly written in that respect.

>Second, some species frequently mentioned in CP texts but
>considered sub-carnivorous for some reason are nevertheless listed in
>the database, and explicitly marked as "sub-carnivorous" or "non-
>carnivorous" in the "C:" (comment) field, sometimes with a short
>explanation.

*This* is the point I am trying to make. I think a couple of very simple
qualifiers should be added to the opening remarks of the database, stating
that all the species included are treated as being carnivorous (or not)
according to the definition which *you* have constructed and applied there.
You could then add that other definitions have been published and that
readers should refer to these if they wish to investigate the issue
further. You could do the same with *your* taxonomic interpretations,
particularly those which are at variance with others which have been
formally published. By doing this, you could (for example - and this is
certainly not a debate I wish to get sidetracked into again!) continue to
recognise N. fallax as being distinct from N. stenophylla and Jebb & Cheek
could continue not to, without there being any direct, unsubstantiated
implication on the database that the alternative views are wrong (even if
you or others think they are).

The problem with the database at present is that you have nowhere to
promote, defend or provide evidence for your views, whereas authors of
papers etc do. Thus, unless you provide the qualifiers that I have referred
to above, and/or acknowledge the fact that alternative opinions have been
published, the impression is given that you have disregarded the
alternative opinions, without saying why. The result is that the scientific
value of the database is diminished. I think the power of the databse would
be magnified greatly with the few small changes outlined above. Then,
rather than appearing as a taxonomic stand-off between you and various
other scientists (and believe me, from a scientific standpoint, this is how
it looks!), it would be clear to everybody that a serious, ongoing
scientific debate is in progress and that no conclusion has been reached on
many issues yet.

So, rather than attacking you or the database, I am simply trying to air my
views and express the desire that it becomes a more useful resource to the
scientists who work with CP. What I have mentioned above would, IMHO, be a
very useful, conciliatory first step in this direction. Then, if you have
time (and this is a big "if" - I'm sure you're very busy), you could
perhaps add some little bits of text pertaining to the more controversial
elements in the database (there need not be too many of these), in which
you could state your opinions and how/why you arrived at the conclusions
you did.

>I just do not want to (and I doubt anyone ever will) add *all*
>bromeliads or *all* plants with sticky parts, because this would
>turn the database into a big mass of noise with only trace amounts of
>signal remaining (adding the bromeliads alone would inflate the
>database more than fourfold, with absolutely no gain in significant
>information).

I don't recall suggesting or implying that this would ever have to be done.

>Apart from the fact that I would no longer be able to maintain and
>update the resulting monster appropriately, with any added data of
>low relevance, the need to add further data with even less relevance
>would grow. If you want to catch even traces ow gray, you must
>include the whole scale with the only exception of pure white.

I think you have done an effective job of drawing the line between CP and
non-CP. However, because the position of this line is a matter of personal
opinion, I think that the "absolute" statements need qualification for the
reasons outlined above. It's a matter of personal preference and respect
for the views of others as much as it is about science.

OK, I've had enough for today! For the time being, at least, I don't wish
to be drawn into the debate about sub-CP for three reasons:

1. I don't think most of the subscribers to this list could stand it!

2. I don't want to run even the smallest risk of having several K worth of
carefully written text greeted simply by the word, "invalid" (something you
have done to me on at least one previous occasion, Jan)! I don't have time
for that.

3. I never entered it in the first place - I was drawing attention to the
way the debate was being conducted, that's all. If I do get involved, the
points I am trying to make here may well be lost in the ensuing melee.

Now I'm going back to the lab to watch hermit crabs fight each other! :-)

Cheers,

Charles.

PS. Richard Ellis - I think you are largely correct and the benefits of
carnivory to plants can be quantified without too much difficulty for many
species! Anybody who is interested should see the following paper:

Moran, J. and A. Moran. 1998. Foliar reflectance and vector analysis reveal
nutritional stress in prey-deprived pitcher plants. International Journal
of Plant Sciences. 159(6): 996 - 1001.



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