re: sub-carnivores

From: Nicholas Plummer (nplummer@duke.edu)
Date: Wed Oct 28 1998 - 05:45:18 PST


Date: Wed, 28 Oct 1998 08:45:18 -0500
From: Nicholas Plummer <nplummer@duke.edu>
To: cp@opus.hpl.hp.com
Message-Id: <aabcdefg3426$foo@default>
Subject: re: sub-carnivores

Jan Schlauer (SCHLAUER@chemie.uni-wuerzburg.de) wrote:

> Apparently none of the bromeliads has endogenous hydrolytic activity
> in their "traps". Bromeliads and similar cistern-forming monocots are
> adapted at accumulating all sorts of living and dead debris as a
> compensation for the missing substrate in their habitats (many are
> epiphytic). This is a specialized form of soil generation/
> accumulation, not carnivory in the sense we discuss it here.

The literature I've seen on Brocchinia suggests that:

1. It grows in the open, so it's not going to collect much organic
debris in the way that an epiphytic bromeliad would,

2. The tight rosette is a poor shape for generalized collecting of
debris, but it works well as a trap.

3. Young plants secrete a nectar-like fragrance similar to that of
Heliamphora.

4. The plants trap large numbers of ants, the same species that is
trapped by Heliamphora in the same habitat.

Given these observations, wouldn't it be reasonable to consider
Brocchinia "proto-carnivorous" or something similar. It seems probable
that carnivorous pitcher plants evolved from more generalized debris
traps, and intermediate stages probably had a trapping mechanism before
they evolved digestive enzymes. Brocchinia does not appear to be just
another typical tank-forming bromeliad.

I've never been a fan of strict black-and-white categories in biology.
There are almost always exceptions :-) For example, hasn't it been
suggested that Nepenthes lowii obtains much of it's nutrients from bird
droppings? If so, is it still carnivorous? Maybe post-carnivorous?

cheers,
        Nick

---------------------
Nicholas Plummer
nplummer@duke.edu
http://www.duke.edu/~nplummer/



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