Also, Tipularia discolor, native to the eastern United States, has asymmetrical flowers with the lip askew one direction and the dorsal sepal and petals skewed the other direction.
I seem to recall reading that T. discolor is pollinated by moths, and the skewed flower ensures that the pollinia are deposited on the insect's compound eye. A symmetrical flower would lead to the pollen being deposited on the moth's scaley forehead, where it would not stick well.
Can't recall where I read it, so I don't know if it is true. I'd be curious to know if Tipularia flowers always skew the same direction. If not, and if the direction is under genetic control, it could be a mechanism for reproductive isolation and, ultimately, speciation.
Nick
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Nicholas Plummer
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