Which Came First: The Flower or the Bee?

April 11, 2013

As I watch spring emerge in the Bee America apiary—tiny green buds unfurl from the tips of branches, blossoms emerge from flowering trees, and honeybees swoop out of the hive on reconnaissance missions—I started to wonder about the complex relationship between bees and plants. Recently, a research group headed by Geraldine Wright, a honeybee brain researcher at Newcastle University in England, published an article in the prestigious scientific journal, Science, that the caffeine-laced nectar of citrus plants enhances a honeybee’s ability to learn and hence return to pollinate the same flowers. These findings suggest plants that naturally produce caffeine (and other addictive substances like nicotine) act to change an insect’s behavior for their own benefit, i.e., attract more pollinators to their flowers.

It has long been known that plants produce a variety of chemicals that modify animal behavior such as energy-rich sugars in their nectar, enticing fragrances, and attractively colored and patterned petals, etc. What’s fascinating about Dr. Wright’s caffeine study is that it demonstrates certain plants can influence the memory—and not just the behavior—of pollinators through the use of a psychoactive drug. And what’s even more amazing…it is the same substance that many of us drink every day in our coffee, tea and soft drinks!

Bees help flowers make new flowers by transferring pollen from one bloom to another bloom and we know that this process is enhanced by a plant’s unique properties. We have also just learned that if it is a citrus plant, it is also aided by its ability to produce caffeinated nectar. But what is much less well understood—even by entomologists and botanists—is the intricacies of the co-evolution of plants and bees. Essentially—which came first, the bee or the flowering plant? Up until recently there was a discrepancy in the fossil records…suggesting that angiosperms (flowering plants) emerged much earlier than any known pollinators. However, in 2006, the discovery of a 100-million-year old bee embedded in amber in the Hukawng Valley of Myanmar suggests that early bees and flowering plants may have been contemporaries. This discovery of the ancient bee opens the door to the intriguing possibility that such pollinators enabled the rapid expansion and diversity of flowering plants (which depend upon means other than wind to spread their seeds). Prior to the angiosperm’s ascendency, the prehistoric world was covered by gymnosperms, mainly ferns and conifer trees that used wind power for pollination.

It is conceivable that bees may have driven the evolution of early flowering plants rather than the other way around, which was previously hypothesized. Primitive angiosperms may have taken advantage of bee behavior by developing various colors and scents for their flowers as a pollination strategy to compete with gymnosperms. While coming on the scene later than the earlier gymnosperms, angiosperms—with the help of bees and other pollinating insects—have certainly ended up flourishing in modern times. To date, there are 250,000 species of angiosperms compared to less than 15,000 species of gymnosperms.

So, while it’s too early to know whether caffeinated nectar improves a bee’s memory, as Dr. Wright and her study suggest, or just encourages the bees to seek out more of the stimulant, it’s a perfect example of how flowering plants have evolved effective strategies to capture an insect’s attention and use it to their advantage. What particularly excites me about this study, and the contemplation of the evolution of bees and flowering plants, is that this knowledge may ultimately be helpful in restoring the declining honeybee population. The precipitous decrease in the number of honeybees has devastating implications for the future of our ecosystem and the stability of our food supply. Understanding what motivates honeybees to continue the essential work of pollination could lead to strategies that may ensure that these insects are able to remember and pollinate their favorite flowers.