I don't have anything to add to this discussion, but I DO have questions
regarding the evolution of CPs that this thread, as well as the discussion
about Pietropaulo's introduction have raised, particularly around the
issue of adaptation. First of all, the general assumption I have gleaned
from the materials I've read about CPs is that CPs have evolved TOWARD
carnivory. Is there any evidence (maybe Roridula?) that plants have
evolved FROM previously carnivorous forms to their present non-carnivorous
states.
I began to ask myself this after rereading Pietropaulo's introduction,
especially the passage about the gradual and unnatural/natural conversion
of wetlands to drylands. One of the major *causes of* natural selection
is unstable habitats. Individuals which possess variations suitable for
the changing habitat survive to reproduce, and soon out-compete the parent
population. If there aren't enough individuals possessing the beneficial
variations, both populations die out as the habitat becomes more and more
inhospitable. Could this be what has happened with Roridula, only in
reverse? Did its habitat IMPROVE to the point where carnivory was no
longer necessary, its present form reflecting this adaptation? By the
same token, Brocchinia *becomes* carnivorous, because absorbing nutrients
from hapless invertebrates proved to be more efficient than absorbing them
from the environment. In this scenario, the habitats and the species are
in flux, while carnivory, as a survival strategy among all plants, remains
constant. I guess this provides a dim ray of hope for those who believe
carnivorous plants are on the decline. Unfortunately, it may not shine
down on them during their lifetimes.
I hope this stimulates discussion.
Gary