The sheer number of the most common species in an ecosystem — rather than the level of biodiversity — determines how much the system benefits people.

Conservationists have argued that biodiversity supports ecosystem services such as crop pollination. To separate out the effects of species richness from species abundance, Rachael Winfree of Rutgers University in New Brunswick, New Jersey, and her colleagues used an equation from evolutionary biology to analyse wild-bee pollination of fruit crops.

The team counted thousands of individual bees from as many as 56 different species in fields of watermelons, blueberries and cranberries, as well as the average number of pollen grains they deposited on flowers. They calculated that pollination was dominated by a few common bee species.

Loss of rare species would not change pollination rates much, but reductions in the number of common bees would make a huge difference, the authors say.

Ecol. Lett. http://doi.org/4m5 (2015)