Pollination Plasticity

Pollinators are great -- that is, unless they also feed upon the plant they are pollinating. In the arid regions of western North America, Nicotiana attenuata, sometimes referred to as coyote tobacco, has this very problem. 

Blooming at night, its white flowers are heavily scented in order to attract its pollinator, a species of hawkmoth. Female hawkmoths do a little bit more than just grab a sip of nectar. Their larvae feed on members of the tobacco family and, as anyone with tomatoes can tell you, they have a voracious apatite. Visiting female moths take the meal break as a chance to lay their eggs. Researchers noticed a strange thing about N. attenuata plants that had feeding damage from hawkmoth caterpillars, their flowers seemed to change.

And change they did. Plants with caterpillars begin producing flowers that open during the day, instead of at night. The plants also stopped producing a scent. What's more, the flowers didn't open very far either. What was the reason for these drastic changes? Are the plants stressed out from the caterpillar attack?

Not exactly. In fact, the answer is quite remarkable. As it it turns out, plants with caterpillars munching on them were intentionally shifting their entire reproductive strategy to avoid the larvae of their intended pollinators. Flowers that open during the day no longer attracted the attention of moths, which may lay eggs on the plant. Instead, the flowers became quite attractive to hummingbirds. Hummingbirds are quite effective as pollinators and their offspring don't eat the plants that their parents feed on. 

So, how does the plant know when its being fed upon? As it turns out, chemicals in the saliva of the caterpillar trigger a chemical response within the plant that tells it to start ramping up defenses (of which nicotine is such a defense). This signaling cascade also tells the plant to start producing day opening flowers instead of night opening flowers. It just goes to show you how a little attention to detail can uncover some amazing aspects of the world around us. 

Photo Credit: Danny Kessler, MPI chemische Ökologie

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