Toxic nectar to improve pollinator fidelity?

Amy L. Parachnowitsch
Plant Ecology and Evolution, Evolutionary Biology Centre, Uppsala University, Uppsala, Sweden 75236. email: amyparachnowitsch@gmail.com

Maybe because so many of us rely and enjoy caffeine (I’m sipping a large cup of tea as I write this), a recent Science paper on flowers dosing their nectar with caffeine has made quite an impact in popular media. You can find accounts of the paper at New York Times, National Geographic, ScienceNews and pretty much any news source you care to read. The blog world also is a buzz (excuse the pun) with this paper. Everything from science blogs such as Scientific American, Discover, Addiction to food/barista sites (Home-Barista, Foodbeast, Champagnewhisky) are talking about this research.

What makes this particular article so interesting to so many? On the surface, this story touches upon things which people are generally intrigued about: drugs and improving memory. It doesn’t hurt that the drug involved, caffeine, is one people are familiar with and most have directly experienced. There are plenty of good descriptions of this research (including the original article and its summary), and I suggest taking the time to read the full story. In short, Geraldine Wright and coauthors discovered that bees could remember floral cues (scent) better if the reward they received contained caffeine via the caffeine’s action of stimulating the bees’ brain cells. Moreover, plants that produce caffeine in their nectar seem to do this at a level that is active but not so high that bees will reject the nectar because of the bitter taste.

Beyond our interest in drugs and memory, I think what makes these kinds of stories resonate so strongly with non-scientists is that plants are often viewed as static things that we (or other animals) exploit. Rarely do people consider that plants might actually be exploiting us (or other animals), although Mikael Pollan popularized this concept in his best seller The Botany of Desire. Of course, those studying plants have no difficulty seeing that plants do behave, and that evolutionarily, they have been selected to exploit animals in all kinds of ways.

Image courtesy of Geraldine Wright

Bee on citrus flower. Image courtesy of Geraldine Wright

As a pollination biologist and evolutionary ecologist, I’m interested in these findings because the work adds to our understanding of the co-evolutionary interactions between flowers and their pollinators. By improving memory of pollinators these plants may increase pollinator fidelity, suggesting that an important function of ‘toxic nectar’ may be to manipulate pollinators. However, secondary compounds in nectar are common (e.g. toxic nectar), and much work remains to understand the ecological and evolutionary roles of these different components of floral reward. I am excited to see research programmes such as those of this group (and others) proceed because their work hints at the growing trend of approaching floral phenotypes in a holistic way. In this study, caffeine found in the floral nectar enhanced bees memory of floral scent. Thus, to appreciate the role of reward (nectar), secondary compounds found in the reward (caffeine) and scent, it was necessary to study all of these components together. The more we integrate different aspects of floral phenotypes into research programmes, the better we will be able to understand the amazing floral diversity we see.

References

Adler LS. (2000), The ecological significance of toxic nectar. Oikos, 91: 409–420. doi: 10.1034/j.1600-0706.2000.910301.x

Chittka L and Peng F. Caffeine Boosts Bees’ Memories. Sciences. 2013. Vol. 339 no. 6124 pp. 1157-1159. DOI: 10.1126/science.1234411

Wright GA, Baker DD, Palmer MJ, Stabler D, Mustard JA, Power EF, Borland AM, Stevenson PC. Caffeine in Floral Nectar Enhances a Pollinator’s Memory of Reward. Science. 2013. Vol. 339 no. 6124 pp. 1202-1204.

Pollan M. The Botany of Desire (2001). Random House, hardcover: ISBN 0-375-50129-0, 2002 paperback: ISBN 0-375-76039-3

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Flowering Newsletter published by the Journal of Experimental Botany
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One Response to Toxic nectar to improve pollinator fidelity?

  1. PK Read says:

    “Rarely do people consider that plants might actually be exploiting us” – Yes! I declined to go into this on my short post on this topic because this is a large conversation, but thank you for bringing it up. I think people resist the notion that plants exploit other creatures (esp. humans) because it implies (but doesn’t necessarily correlate with) the consciousness of a kind we don’t attribute to plants. I look forward to any other thoughts you have on this.

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