Bulbophyllum is the largest genus of the orchid
family, with about 2000 species that are mainly pollinated by flies. Many of
these species are known for releasing odours that humans find unpleasant. There
are, however, many Bulbophyllum species whose flowers specifically
attract true fruit fly
pollinators – especially certain fruit fly pest species – with spicy or
pleasant floral odours.
Non–nectar-producing
and non-resupinate (untwisted floral stalk) solitary flowers of Bulbophyllum
pratervisum emit pleasant floral fragrances to specifically attract and
reward male fruit flies. They have slippery surfaces on their lateral sepals that
specifically aid in pollination. Although pollinia (packages containing fine
pollen grains) removal by male fruit flies has been observed frequently, the
depositing of pollinia to complete pollination (by two males belonging to
different fruit fly pest species) has only been observed recently.
Field
observations show two previously unreported movements of floral parts – a) petals
and medial sepal during daily closing of flowers (for the night, to deter
unwelcome visitors) and reopening (to welcome fruit fly visitors/pollinators),
and b) the spring-loaded, hinged lip (a highly modified petal) during removal
and deposition of pollinia by a male fruit fly.
Additionally, a third (novel) movement has been
observed, either when the flower closes for the night to protect the stigma, or
after a fly has deposited the pollinia onto the stigma – the 'acute tooth' on
each column wall folds inwards to secure the newly deposited pollinia, like a
mother hugging an infant close to her chest.
Read the scientific publication in JPE.
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