Tiny bees are better than large ones at pollinating

Long-distance relationships can be difficult when you’ve put down roots and have no ability to move. For trees, as with most flora, this means relying on matchmakers – bees – to facilitate the fruitful liaisons required for propagation of the species. 

In this botanical sex-work it has generally been presumed that bigger is better, on the basis larger bees can carry more pollen and fly further. Not so, according to conservation biologist Shalene Jha and her fellow investigators of pollination diversity at the University of Texas at Austin, and the University of Panama. 

Their latest research, looking at the pollination services provided by bees within the Panamanian landscape, shows the most productive work is done by native species barely bigger than rice grains.

“Size isn’t everything,” says Jha of the scientists’ finding that tiny bees visit more flowers than their larger counterparts, and cover equally long distances during their foraging – equivalent, in terms of body size, to a human travelling more than 1800 kilometres. 

The study shows small bees were responsible for the bulk of successful pollination between trees more than two kilometres apart. As with humans, the fruitful reproduction between geographically distant trees contributes to genetic diversity and promotes adaptation to disease and environmental changes.

The research project, which took about four years, mapped trees and bees in three sections of tropical rainforest. The researchers calculate the area of study was about 10 times bigger than previous projects also seeking to track bee pollination services. 

“If you work in a small portion of forest you’re only capable of measuring pollen movement in a small area,” Jha explains. “We picked up the signal about how far these little bees move because we started doing work that was commensurate with the scale at which they’re actually flying.”

With most research having focused on bigger bee species, Jha expresses hope that better understanding and appreciating the role of small pollinators can lead to better agricultural conservation practices. It could be particularly useful for restoring degraded ecosystems, since smaller bees have often shown more resilience in the face of habitat destruction.

The research is published in Proceedings of the National Academy of Sciences.