CP evolution, volume II
Fernando Rivadavia Lopes (ferndriv@usp.br)
Thu, 9 Nov 1995 17:21:01 -0300 (GRNLNDST)
A few months ago we discussed CP evolution, comparing the Drosera
in Australia, S.Africa, and S.America. The other day I was thinking about
another aspect of that discussion. What we've heard and read is that in
Western Australia, each species is adapted to a specific kind of soil.
Though numerous species may occur in a small area, each pygmy or tuberous
species has it's own microhabitat defined mostly by the type of soil.
I assume that all the differences we see in leaf shapes, sizes,
and disposition reflect a specialization for trapping different
organisms. Maybe the erect tuberous Drosera species are specialized in
trapping flying insects while the flat, rosetted tuberous and pygmy
Drosera could be specialized in small, crawling or hopping insects. In
these 2 groups, each Drosera species might be specialized in capturing a
specific insect species or a small number of species.
I also assume that the differences observed between flowers of
pygmy and tuberous Drosera, with all those colors plus varying numbers
and shapes of pistils and stamens, reflect a specialization towards
specific pollinators.
Thus, I have never heard of studies proving that there really are
specific prey or pollinators of Drosera in Australia, but I imagine this
specialization does exist. So assuming these exist and adding the habitat
specialization which is known to exist, I ask myself WHY do these exist?
Could it be that intense speciation and specilization is a
natural result of the quick and forced evolution we discussed, caused by
the changing climate in Australia over the past few million years? Why
should the species become specialists and not remain generalists? Is it a
natural step to always go from generalists to specialists? Aren't
generalists said to be better in the sense that they would more easily
adapt to changing habitats? Or is it better to have a large number of
specialists to survive constant habitat changes? Is it possible for
numerous generalist species to live together in a small area and compete
for similar necessities?
I wonder if the numerous Nepenthes species found in Borneo, for
example, are each specialized in trapping specific prey, being
pollinated by specific insects (which would be a natural barrier for
mass hybridization), and growing in specific habitats (altidudes
included)?
ANYONE??
Fernando Rivadavia
Sao Paulo, Brazil