Re: What is a carnivorous plant?

Jan Schlauer (Jan@pbc-ths1.pci.chemie.uni-tuebingen.de)
Mon, 12 Jun 1995 12:17:25 +0100

Peter,

> I'm afraid I don't
> have the 1986 CPN with your article either, so my understanding of
> your counter-argument is also limited - please excuse me if I
> mistakenly ascribe criteria to your definition that are inaccurate.

My argument in that article was not at all detailed, I just mentioned that
certain taxa were not included in the synonym list.

There are several categories of cps (I like the term "cp syndrome" by
JUNIPER & al., i.e. a combination of criteria).

The cp in the strictest sense are all species of Droseraceae,
Cephalotaceae, Byblidaceae, Nepenthaceae, _Triphyophyllum_, and
Lentibulariaceae. These plants are able to

>>attract, catch and digest animals for some nutritional benefit<<.

_Triphyophyllum_ is a part-time carnivore with trapping leaves only on
young shoots, a remarkable parallel to _Tozzia_ (Scrophulariaceae, *not*
closely related phylogenetically!), which is a part-time subterraneous
holoparasite (for the most of the life-cycle, i.e. several years), only to
produce short-lived green flowering shoots, both being monotypic genera
within families which have some completely autotrophic members.

Next come the Sarraceniaceae (some of which lacking proteolytic enzymes),
but the family being evidently of monophyletic origin, and the trapping
device being of a remarkably uniform structure. As the family does contain
some "complete" cps (fitting the above cited criteria) in two of three
genera, I am still tempted to call the whole family carnivorous s.l..

Then come non-cps which approach cps from some side (bromeliads,
_Roridula_, _Ibicella_, _Dipsacus_, _Lathraea_, and many, many more), all
of which lack at least (own!) proteolytic enzymes (there are rumours
however that _Ibicella_ does have them, but I have not seen any of the
proof, and then there is still the question of resorption).

An finally, some very few examples of plants are known (e.g. _Poa annua_,
_Lemna minor_) which do (perhaps) not fit any of the criteria necessary to
be called a cp.

So in this concept Saraceniaceae are already on the borderline (or rather
border-zone, there are no clear cut lines, v.s.), and Bromeliaceae and
_Roridula_ are already far beyond. These plants could perhaps be called
"subcarnivorous" (they have some of the adaptations needed for carnivory
but lack some others), another term "precarnivorous" sounds too
teleological (we can not really predict the course of evolution), and
"hemicarnivorous" suggests that the others were "holocarnivorous" plants
(i.e. completely heterotrophic, without chlorophyll in analogy to
holoparasitic plants), which have not been discovered yet.

Kind regards
Jan