Using a uniquely comprehensive checklist of bee distributions and over 5,800,000 public bee occurrence records, a team of researchers from China, the United States and Singapore has described global patterns of bee biodiversity. Their results show that there are more bee species in the northern hemisphere than the southern hemisphere and more in arid and temperate environments than in the tropics.
Many plants and animals follow a pattern, known as a latitudinal gradient, where diversity increases toward the tropics and decreases toward the poles.
Bees are an exception to this rule, having more species concentrated away from the poles and fewer near the equator, a pattern known as a bimodal latitudinal gradient.
There are far fewer bee species in forests and jungles than in arid desert environments because trees tend to provide fewer sources of food for bees than low-lying plants and flowers.
“People think of bees as just honey bees, bumblebees, and maybe a few others, but there are more species of bees than of birds and mammals combined,” said co-lead author Dr. John Ascher, a researcher at the National University of Singapore.
“The United States has by far the most species of bees, but there are also vast areas of the African continent and the Middle East which have high levels of undiscovered diversity, more than in tropical areas.”
To create their map, the scientists compared data about the occurrence of individual bee species with a massive checklist of over 20,000 species compiled by Dr. Ascher and accessible online at the biodiversity portal DiscoverLife.org.
Cross-referencing multiple datasets with complementary coverage resulted in a much clearer picture of how the many species of bees are distributed in different geographic areas.
This is an important first step in assessing the distribution and potential declines of bee populations.
“We’re extremely interested in abundance of bees, but that’s something that has to be done in relation to a baseline,” Dr. Ascher said.
“We’re trying to establish that baseline. We really can’t interpret abundance until we understand species richness and geographic patterns.”
While there remains a lot to learn about what drives bee diversity, the authors hope their work will help in the conservation of bees as global pollinators.
“Many crops, especially in developing countries, rely on native bee species, not honey bees,” said co-lead author Dr. Alice Hughes, a researcher in Xishuangbanna Tropical Botanical Garden at the Chinese Academy of Sciences.
“There isn’t nearly enough data out there about them, and providing a sensible baseline and analyzing it in a sensible way is essential if we’re going to maintain both biodiversity and also the services these species provide in the future.”
The team’s paper was published in the journal Current Biology.
Michael C. Orr et al. Global Patterns and Drivers of Bee Distribution. Current Biology, published online November 19, 2020; doi: 10.1016/j.cub.2020.10.053