NEPENTHES taxonomy

Matthew Jebb (
Tue, 20 Sep 94 09:47:01 +0100

Dear Jan and all other followers of Nepenthes taxonomy,

I am still interested in an informal discussion. That's why I suggested
sending you the completed descriptions in due course and before they are
published. I have already sent Andreas a set of preliminary Sumatran
drawings, since I have no desire to be secretive about my information,
taxonomy is not a matter of copyright nor one-upmanship. I regard this
forum as a place to discuss the species and their biology, but not the
nomenclatural minutae, which makes dull reading for the majority of Bulletin
board readers. I think by and large we are in agreement on what species are
present, so how about a bit of biology, and a discussion of WHY Nepenthes
are what they are...

1.Do all Nepenthes use their pitchers PRIMARILY for insect capture?

Perhaps not? N.lowii, N.ampullaria, N.infundibuliformis, N.dubia and
N.inermis have unusually wide, open mouths and tiny lids. They are poor at
preventing rainwater getting in, and many people report N.lowii as very
effective litter traps, often filled with dead leaves. Maybe the leaf-heap
is very attractive to thrips and beetles who in living their regularly
become trapped. This is analogous to the symbiotic relationship theory
proposed by JOEL, in which ants regularly feed on the nectar glands of
Sarracenia and Nepenthes, and only rarely get caught, thus ensuring that the
ant-colony continues to remain interested in the nectar source (through
communicated recruitment to the source), whilst not unduly upset to see
their aged aunties tumbling to their deaths, and thus ensuring a happy
carnivore continues to supply them nectar.
Alternatively something else may be occurring - both N.inemris and
N.infundibuliformis have very viscous pitcher fluid, but why?? The
coincidence of pitcher shape may be significant.


Nepenthes, rather than being a group of plants that has evolved to occupy
marginal environments, can be just as easily looked upon as a group of
plants TRAPPED in marginal habitats. Being a carnivore is a very energetic
lifestyle, largely because your food is so full of protein and fats, so your
cell metabolism becomes dominated by these rather than sugars (see JUNIPER,
JOEL and ROBBINS) - as a consequence high light levels become of major
importance in driving these plants with their 'animal metabolism'. Some
species, however, CAN live in very low light levels. N.ampullaria for
example appears to achieve this by separating big-bladed, pitcher-less
leaves from large-pitchered, but blade-less leaves, the former on tall
climbing stems, the latter on terrestrial or low level rosette leaves, often
in deep shade. Other species which I have encountered in shady locations
often don't make pitchers until they have grown taller, whilst rosette
plants in full sun are often dominated by pitchers and have small leaves.
N.burbidgeae is another shade-loving species. Often this species will show
relatively small pitchers to the size of its leaves, again this MAY be an
indication of the constraints of light level vs. the need to digest.

3.This leads on to the question of INDIGESTION in Nepenthes.

Sounds funny, but in fact overfeeding CPs can be lethal. Possibly plants
running below an optimum light level may be overwhelmed by an excess
quantity of prey. In low light levels it may therefore be better to
dispense with, or have very small pitchers (cf. shade grwoing plants,
N.burbidgeae). N.ampullaria separates the two. The mysterious N.mollis of
Borneo might be doing the same thing - It is only known by a single specimen
with plenty of leaves and inflorescences, but not a single pitcher - when
collecting Nepenthes this is an unusual part of the plant NOT to collect,
unless there weren't any around.

Some of these questions need plenty of controlled experiments to be
PROVED, but meanwhile circumstantial evidence by growers and people who have
seen these plants in the wild can help in answering a lot of problems. The
shape of many Nepenthes pitchers can be diagnostic for the species, but WHY
they are the shape they are can be puzzling. From my own limited data on
N.mirabilis it can be seen that there IS a difference in what upper and
lower pitchers capture, which MAY be related to their morphology as well as
their physical position, as has been shown with regard to the heights of
Sarracenia pitchers (Incidentally have people noticed how the leaves of many
of the TALL Sarracenia species are produced in pairs, one growing taller
than the other?).

Some other Nepenthes-puzzlers include:

4.Why does N.reinwardtiana have those extraordinary eye spots?

5.Why is the peristome of N.hamatus, N.edwardsiana, N.villosa, N.macrophylla
the shape it is? What do these species capture compared to other species in
the same habitats?

6.What are the lid hairs of N.lowii, N.ephippiata, N.macfarlanei for?

Answers to all these questions would be of significance to solving
Nepenthes' evolutionary history. Some species no doubt (APPEAR TO?) form
related groups: tentaculata-hamatus-reinwardtiana-murudensis,

By and large Danser's sub-groupings (not his overall groups) still hold up,
but at present we are still left with a mass of small related groups whilst
the overall picture is most unclear. Morphological characters in such a
morphologically constrained group are most unlikely to give any resolution.



Matthew Jebb,
School of Botany,
Trinity College Dublin,
Dublin 2, Tel: +353-1-702 1421
IRELAND. Fax: +353-1-702 1147