Floral curve test shows what’s great for a moth is not so good for a flower

PORTLAND, ORE. — A great flower shape for a moth trying to get a drink in the dark turns out to be awful from the plant’s point of view.

Offering hawk moths (Manduca sexta) a range of 3-D printed flowers with different curvatures shows that a moderately curved trumpet shape lets moths sip most efficiently, Foen Peng reported June 24 at the Evolution 2017 meeting. That’s a win for a nocturnal flying insect searching for nectar.

Yet drinking ease wasn’t best for the plant. During swift sips, the moths did less inadvertent bumping against the artificial flowers’ simulated sex organs than moths struggling to sip from an inconvenient shape. Less contact with real flower parts would mean less delivery and pickup of pollen.

Peng, of the University of Washington in Seattle, offered the moths three other shapes besides the gently curved trumpet. The best for the plant was a flat-topped “flower” with a right angle drop to a nectar well in the center. Previous work suggested that lack of curves made it very difficult for hawk moths hovering above a flower and extending their tonguelike proboscises to tap and probe the way to nectar in dim light.

Pollination at first glance may look like an easy mutualism evolving with the best interests of both plant and pollinator. But these experiments reveal a hidden, underlying conflict, Peng said.