In a recent paper published in Scientific Reports, Irmgard Schaffler and colleagues (Schaffler et al 2015) described an exciting communication system between oil-collecting bees and oil-producing flowers, the FIRST truly private message between a pollinator and host plant.
While most flowering plants are pollinated by a diverse array of organisms which visit it, there are some species which have developed highly specialised systems contemporaneously with one group of organism. One such example is that between oil secreting plants and their oil-collecting bee pollinators. Hooray for that!…I am of course (he says in as serious a voice as possible), completely unbiased and my interest in the paper has nothing to do with the fact that I am studying Diascia and Rediviva for my PhD. Although it is fantastic to learn something new about the group you are working on!
Schaffler and colleagues described a specialised compound which they named Diacetin (hmmmm I think Diascia may have been an influencing factor…). This fatty acid derivative was found to elicit strong antennal responses in the oil collecting bees tested.
They tested this by hooking up the antennae of melittid bees from both Europe (Macropis) and South Africa (Rediviva) and undertaking multiple electroantennograms. Basically, this involves the study of electrical impulses in the antennae of the bees, whereby the scientists are able to detect the response of a bee when exposed to different chemical compounds. Interestingly there were no significant antennal responses in non-oil collecting bees and not even in the honey bee (Apis mellifera). This suggests a private sensory channel between the bee and its host plant. What they also found is that Diacetin occurs in several families of floral oil plants around the world- which therefore suggests that this compound has evolved independently multiple times, along with the ability of unrelated flora to produce oil (which the bees use to feed their larvae and line their nests). The relationship between the bee and the flower is an example of an obligate mutualism, I.e. the bee is the sole pollinator of the plant and the oil produced by the plant often the only source available to the bee.
This finding is fascinating given that it is yet another example of the co-evolutionary relationship between Diascia flowers and Rediviva bees, along with the gigantic forelegs of the bee and spur-length in the flowers.
It allows bees to rapidly and easily locate the floral oil rewards produced by host plants, a message/cue which other potential pollinators are completely unaware of! Science at its best 🙂