Re: Drosera and ants

Bob Beer (bbeer@u.washington.edu)
Thu, 25 Aug 1994 10:01:38 -0700 (PDT)

> Carnivorous plants, on the whole, are somewhat disappointing in the
> way they set seed. Most CP seeds are heavy and don't go far when
> carried by the wind. You'd think a better survival trick, other than
> evolving to eat insects, would be to have seeds with little parachutes
> (like Dandelions) that float in the air for miles, or even hundreds of
> miles.

Such a characteristic is favaroable for a plant like a dandelion, which
can survive in just about any kind of soil, with this ability being its
edge for survival. However, carnivorous plants have evolved an ability
to live in a more specific type of habitat that not as many plants could
survive in. This was the edge they had to help them survive (until
habitat destruction became a recent problem), and it would be
counterproductive for them to scatter seed extremely widely, with 99
percent of it landing in areas unsuited for their growth. As the seed
that fell close to the mother plant has a better chance of surviving,
because of falling into suitable ground, it is the heavier seed character
that is more likely to be passed on. This is also true for many other
plants that inhabit specific localized habitats, such as many alpines. It
would do them no good to spread their seed into areas where it would have
no ecologicla advantage.

As it is, CP growth tends to be very localized and in clumps.
> And their seeds tend to be poor germinators except under absolutely
> ideal conditions. I would think a better survival trick would be
> for CPs to become epiphytic, grow in trees where there are more
> insects

Oh, but there are *lots* of insects at ground level in their habitats.
Ever visit a coastal bog? :0 Especially flies, ants, and some wasps, which
eat just about anything and are attracted to their traps as well.

, have bulbous roots like seaweed in which to store water for
> periods of drought, a vining nature to spread rapidly through
> forests,

Well, you almost have Nepenthes there, though the bulbous roots aren't
much of a necessity in rain forests. Some of them do grow in areas that
experience occasional quite dry periods. But also, a plant growing in
soils that are quite fertile in the first place, such as that of
temperate forest, would have little ecological advantage in trapping
insects, so it is unlikely that a plant with such a character would show
any more liklihood of increased seed production and survival than its
non-carnivorous sister plants.

poisonous leaves to keep insects away,

But they want to attract insects! But it is an interesting thought:
does anyone know if any insects regularly eat Nepenthes leaves in its
habitats?

and pitchers with
> little trap doors that open when an insect triggers a hair and close
> after capture (Like utricularia).

Well, that works for Utricularia, but Pitcher plants would actually lose
prey if their leaves closed after each capture. Since the pitfall works
so well, they can catch a lot more if it is always open.

Nature provides different CPs
> each with a different scheme. Why not all CP schemes into one plant?

Because such a plant (elaborate trapping mechanisms working against each
other) would not be as likely to survive and propagate as the ones with a
single very efficient trapping device.

> I wonder if genetic engineering can create a commercially successful
> CP plant that farmers can grow as an annual between crops?

Maybe, but it would be a very different plant than those existent now.
What would be the attractive mechanism? I would certainly buy a plant
that attracted and devoured mealy bugs!

Bob