My 2 cents is:
I think the plant benefits from the coevolution
in having a "magic bullet" pollinator that hatches
out at precisely flowering season, and is optimally
designed to find and pollinate the flowers...may even be
completely dependent on the plant for other reasons (in
some cases the insect's pheromones are supplied
by the flowers!).
Second, I think orchids are under two extreme
pressures. One is: life in forest canopies is
difficult and essentially "desert." Most of
the epiphytes are CAM plants and, thanks to the
respiration losses they experience in carbon
fixation, are very slow growers. This deficiency
of carbon means that nectar must be protected
from harvest by animals that cannot accomplish
the pollination. Hence a long spur. The other
pressure is lack of large population size. I
think tropical orchids are found in a very rich
environment in terms of numbers of species per
acre. Getting a pollen grain (or pollinium in this
case) to a member of the same species becomes a
significant needle-in-the-haystack problem. A
co-evolution with some species that becomes dependent
on the plant but is "intelligent" enough to be able
to seek and find other individuals in that haystack
becomes the successful solution to achieve pollination.
ross
________________________________________________
( )______________________________________________)
\ Ross Koning \
\ Biology Department \
\ Eastern CT State University \
\ Willimantic, CT 06226 USA \
\ Koning at ecsu.ctstateu.edu \
\ http://koning.ecsu.ctstateu.edu/default.html \
\ Phone: 860-465-5327 \
) Fax: 860-465-5213 )
/______________________________________________/
