[Pollinator] Faithful Bee but orchid "Pre-ejaculates"

[Peter Bernhardt]

Dear Jack:

Here's a recently published paper that takes an odd twist to the story of
the flower "waiting" for the faithful bee.  The orchid self-pollinates in
the bud stage (not too unusual) but then it opens its flowers and is
visited by Apis cerana.  The bee is useless as a pollinator as the orchid
has already pollinated itself.  Once the pollinium is on the stigma it
can't be re-affixed to the bee.

The situation is probably not unique to this orchid species.  Dr. Meier and
I have been continuing my older interest in Thelymitra in Australia.  It's
a vernal-flowering genus. Small-flowered species in this genus often
self-pollinate in the mature bud but then open rather pretty petals on hot
spring days.  Nevertheless, recurrent hybrids have been recorded between
several self-pollinating species and between self-pollinating and
cross-pollinated (large-flowered) species.  Observations by earlier
naturalists noted visitation by syrphid flies that consume stigmatic fluids
and l"nibble" the crumbling pollinia on the stigma.  Hybrids then are
supposed to occur when a fly visits an open self-pollinated flower
transfrring a few grains to the "virgin stigma" of a second species with
open flowers.   We found that syrphids certainly do carry Thelymitra pollen
on their mouth parts although we never found a fly carrying the whole
pollinarium (viscidium, caudicles and pollinia pairs) of a large-flowered
or small-flowered species to date.

Peter
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