CP Evolution

Fernando Rivadavia Lopes (ferndriv@cat.cce.usp.br)
Thu, 8 Jun 1995 17:27:51 -0300 (EST)

> Has anyone figured out how the pitcher plants managed to
> adapt to that form. Bob suggested that the early pitcher
> plants were simply rolled leaves. That suggests that insects
> became accidentally trapped in the base of the rolled leaf
> and the plant eventually evolved to make used of this easy
> food source. Perhaps, the leaf was something like a ping,
> and had sticky hair on the inside that eventually turned into
> a slick digestive surface and dispensed with its glue.
> It puzzles me how these plants could evolve a carnivorous
> digestive tract. How did these plants make that evolutionary
> jump?

I've an idea. We observe many plants today with petioles which
connect to the stem forming a small space where water can accumulate, a
small version of what we see in bromeliads. Maybe this is where the
pitchers began to evolve, moving slowly to the tips of the leaf lamina
(or reducing these), deepening, developing the stomates into
digestive glands, etc.

> > Here's another theory. Perhaps the plants we see today are
> > the descendants of much larger, more ferocious CPs from
> > prehistory. As the climate of the earth grew less warm,
> > and became more difficult to survive in, perhaps CPs
> > evolved into a much smaller form. Could early CPs have
> > trapped much larger prey? And, exactly how old do the
> > experts think CPs are?
> Great mammoths, ground sloths, and sabertooth cats once thundered
> across the plains of primordial North America. Then they mysteriously
> disappered. Was this caused by climate change? By an asteroid impact?
> By hunting by humans who arrived from Asia over the land bridge? No.
> They were consumed and extirpated by the Pleistocene Drosera, capable of
> snaring and strangling a woolly mammoth in its prehensile tentacles!
> (The new human arrivals then killed these Drosera by overwatering and
> pouring Superthrive on the traps).

We also had giant ground sloths, mammoths, sabertoothed cats, and
others in S.America and thus we probably also had these ferocious CPs.
Only they probably didn't like thick rainforests since there have been
reports in the Amazon of a large beast which inhabits the region. It's
one of those bigfoot-type myths among the locals. Except there are some
serious studies being carried out now, after an american scientist
noticed that the stories from various distant parts of the Amazon
described a similar animal and that these descriptions, believe it or
not, match what we call Megatherium, the prehistoric ground sloths which
supposedly perished only a few thousand years ago. Well, who knows?!
After they found that new species of bovine and that new deer in the
forests of Vietnam, why not a ground sloth in the much larger Amazon?
Just a curiosity.

> There have been sporadic rumors of Nepenthes sightings
> in central Africa, but I have never heard of any substantial
> evidence. Wouldn't it be nice?

> I love these sorts of mysteries! Have any of these sightings been
> documented in books or articles?
> I'd like to find out when and where these plants were seen. It is
> too bad people don't get more
> excited about finds like this. If someone saw a giant penguin on
> the side of Mt. Kilamanjaro, it
> would at least show up in the tabloids.
> I'm serious though, I'd like to know more about these sightings.
> It seems like African nepenthes
> are within the realm of possibility.

Ivan Snyder from Los Angeles has told me that a guy he knows who
collects who knows what plant in central Africa has seen Nepenthes there.
Apparently, the guy drew the plant for Ivan, without knowing what it was,
claiming he'd seen it. But the guy claimed it had a large, single flower,
thus I believe he might've been drawing an Aristolocchia (mixing up
flowers with traps).

> Flowers can only be important in terms of evolution in species which
> produce seed sexually. This is most probably not the case in some species
> of SW AU _Drosera_. I do not doubt floral ecology is important in the other
> species. I agree that some of the AU species may be sterile or aneuploid as
> a result of hybridization events in the past.

Exactly what I was thinking. Pollinization would then be
important for most species, except those of recent, possibly hybrid,

> Almost certainly, the first region to become a desert in AU was the N part
> (as soon as it crossed the S tropic). So the now essentially tropical N AU
> species could not have existed there before N AU entered the tropical humid
> zone *beyond* the desert zone (as soon as AU had moved further N). Thus,
> the recent N AU and S AU species of _D._ did have *completely* different
> chorological histories: While the S species were formerly widespread in AU
> (and a few of them also leaving AU), their range was successively
> fragmented and concentrated by the desert successively spreading from NW to
> SE (having reached C AU nowadays), the N species could have established
> only much more recently, maybe having originated even somewhere outside AU.
> It is not at all a surprise that we meet different sets of species in
> (tropical humid) N AU and (mediterranean) SW AU.

Yes, of course! The desert would begin in the northern region!
Then this leads me further into believing that the northern species might
be descended from pygmies and tuberous species which migrated north.

> I do not think the _D.petiolaris_ group (including _D.banksii_:
> Lasiocephala) is in any way comparable with subgen. Ergaleium or subgen.
> Bryastrum. The first is a rather small and essentially tropical set of
> species which have entered the scene comparatively late in the AU history.
> The two remaining are presumably older in AU with a pronounced (more
> recent) centre of diversity in SW AU.

Sorry, you're right, I got them mixed up. It was D subtilis I
meant. Though they might not be similar nowadays, you can't help noticing
how similar they are morphologically, the petiolaris-complex with
the pygmy Drosera and the tuberous species with D.subtilis and
D.banksii. Well, at least more similarities than with other groups.

> I do not believe they knew what awaited them, but one fraction of them had
> the time to adapt and prevent extinction, the other fraction is to be
> sought somewhere in the fossil record.
> There is a tremendous difference between a drier patch in a subtropical
> savanna or campo rupestre somewhat distant from a rivulet with your buddies
> growing under optimal conditions in direct (insect-) flight distance and a
> mediterranean habitat with the desert approaching from one side and your
> buddies forced into the ocean on the other side (the ecological conditions
> in AU were much more global, involving the whole range of the species).

I don't get it, explain with more detail. If you say you believe
the Drosera we see today are relicts of a greater age of these subgenera,
when they were more widespread in Australia, then where does the above
statement fit in, with plants diversifying as they're pressed into their
small areas by the desert. How do the insects fit into this too?

> As you will find in the archives, this question (cf. subject) has been
> discussed at some length on this list in the past. I hope you will find it
> sufficient that I do *not* regard any Bromeliacea as cp (they are
> bromeliads, sometimes forming water cisterns, which is a satisfactory
> description of their features, cf. _Dipsacus_). For further discussion I
> recommend the bromeliad list, not this one.

I haven't checked the archives yet and don't know what was said,
but by what I've heard, that Catopsis produces a sweet smell to attract
bugs, it uses some kind of light trick to confuse bugs (I'm not sure if
just reflection, or UV, or whatever), and it has a fine powder on the
leaves which sticks to insects' feet and make them clumsy, which causes
them to slip and fall into the liquid where they drown.

> BTW: The statement that _Sarracenia_ is devoid of (own) digestive enzymes
> is rather certainly wrong. Endogeneous proteolytic activities have even
> been discovered in the pitcher fluid of some species of _Heliamphora_ (!)
> recently.

Wow, I hadn't heard about this one!!

Sao Paulo, Brazil