There are over 20,000 species of bees, but there is little exact data on how these species are distributed around the globe. Scientists have created a map of bee diversity by combining a global list of known bee species with 6 million public records of where certain species originated around the world. The results are published by Current Biology.
Many plants and animals follow a pattern known as latitudinal gradient, with diversity increasing towards the tropics and decreasing towards the poles. Bees are the exception to this rule. They have more species located far from the poles, and fewer – at the equator. This is called a bimodal latitudinal gradient. There are far fewer bee species in forests and jungles than in arid deserts. The fact is that trees, as a rule, do not provide enough food for bees, in contrast to low-lying plants and flowers.
The findings of the scientists confirm that there are more species of bees in the northern hemisphere than in the southern; and more in arid and temperate climates than in the tropics.
To create the maps, the senior author of the study, John Asher, an assistant professor of biological sciences at the National University of Singapore, and his colleagues compared the frequency of occurrence of individual bee species with a massive checklist of over 20,000 species. The list was compiled by Usher and is available online at the DiscoverLife.org biodiversity portal. The creation of these maps is an important first step in assessing the distribution and potential decline of bee populations.
“I was surprised at how terrible most of the previous global data on bee diversity was,” said Alice Hughes, assistant professor of conservation biology at the Xishuangbanna Tropical Botanical Garden of the Chinese Academy of Sciences and another article author. “A lot of the data was too scattered or too concentrated on a small number of countries.”
While there is still much to be learned about the diversity of bees, the research team hopes their work will help keep bees as global pollinators.
“Many crops, especially in developing countries, depend on local bee species, not honey bees,” Hughes emphasizes. “However, there is almost no data to help us preserve the species.”
The authors see this study as an important first step towards a more comprehensive understanding of the global diversity of bees and an important basis for future more detailed studies of these insects.