Plant Evolution & Pollinator Type Much More Intimately Associated Than Supposed

This is way out there, in relation to what we typically cover here at CleanTechnica, but is something that I decided to cover anyway because of the links to industrial agriculture and food production and the rapid decline of most bee species seen over the last few decades.

New research from the Department of Systematic and Evolutionary Botany at the University of Zurich has revealed that plant evolution is much more intimately associated with pollinator presence and type than has been commonly supposed. To put that another way, pollinator presence (or absence) and type leads to rapid and large changes in phenotype — in only a few generations, rather than over longer periods of time as was assumed.

With regard to the new work, the researchers found that even after only 9 generations, plants were considerably larger and more fragrant when pollinated by bumblebees than if pollinated by hoverflies.

In other words, with bumblebees taken out of the picture, the plants in question ended up much smaller and less productive in only a few generations’ time. Why does this matter? Well, the potential links to food production and the ongoing destruction of wild bee habitats and numbers should be pretty obvious.

The press release provides more: “For their experiment UZH professor Florian Schiestl and doctoral student Daniel Gervasi used field mustard — a kind of cabbage species and a close relative of oilseed rape (canola). The researchers allowed one plant group to be pollinated solely by bumblebees for 9 generations, another only by hoverflies and a third by hand. Afterwards they analyzed the plants, ‘which differed greatly,’ as Florian Schiestl explains. The plants pollinated by bumblebees were larger and had more fragrant flowers with a greater UV color component, which bees and their relatives see. The plants pollinated by hoverflies, on the other hand, were smaller, their flowers were less fragrant and they self-pollinated considerably more. According to Schiestl, the mechanism of evolutionary change is fact that different pollinators differ in their preferences and thus preferentially cross-pollinate specific plant individuals, much like a plant breeder using individuals with favorable properties. The flies’ considerably lower pollination efficiency is the cause of the increase in self-pollination.”

As noted by Schiestl, these findings go against common assumptions: “The traditional assumption is that evolution is a slow process.” The research summed up the findings as: “A change in the composition of pollinator insects in natural habitats can trigger a rapid evolutionary transformation in plants.”

To go over the earlier point about the rapid decline in wild bee numbers seen over the last few decades again, habitat destruction and the use of certain pesticides has resulted in wild bee numbers in many regions plummeting in recent years. A number of species are also thought to have gone extinct in recent decades.

Presuming that this decline continues, many plants may have to rely more on inefficient pollinators like the hoverflies and self pollination, which will lead directly to reduced genetic variability amongst populations and thus greater susceptibility to disease and pests. In addition, of course, the loss of bees would cause enormous problems for crop production of various staple foods.

The new findings are detailed in a paper published in the journal Nature Communications.

Photo via University of Zurich