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There are over 20,000 bee species, but accurate data on how these species spread around the world are scarce. However, the researchers reporting in the journal Current biology on November 19, they created a bee diversity map by combining the most comprehensive global checklist of known bee species with the nearly 6 million additional public records of where individual species have appeared around the world. The team’s findings support that there are more bee species in the northern hemisphere than in the southern hemisphere and more in arid and temperate environments than in the tropics.
“People think of bees only as honey bees, bumblebees, and maybe a few others, but there are more bee species than birds and mammals combined,” says senior author John Ascher, assistant professor of biological sciences at the National University. of Singapore. “The United States has by far the largest number of bee species, but there are also large areas of the African continent and the Middle East that have high levels of unknown diversity, more so than in tropical areas.”
Many plants and animals follow a pattern, known as a latitudinal gradient, in which diversity increases towards the tropics and decreases towards the poles. Bees are an exception to this rule, having more species concentrated away from the poles and less close to 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 food sources for bees than low-lying plants and flowers.
“When it rains in the desert, there are these unpredictable mass blooms that can literally carpet the entire area,” says first author Michael Orr, a postdoctoral fellow at the Institute of Zoology, Chinese Academy of Sciences. “There’s a much higher turnover in the desert because of how uneven the resources are year after year. So there’s a lot of potential for new species there.”
To create their maps, Ascher, Orr, Hughes and colleagues compared the data on the presence of individual bee species with a huge checklist of over 20,000 species compiled by Dr. Ascher and accessible online on the DiscoverLife.org biodiversity portal . Cross-referencing multiple datasets with complementary coverage produced a much clearer picture of how the numerous bee species are distributed across different geographic areas. This is an important first step in assessing the distribution and potential decline of bee populations.
“We are extremely interested in the abundance of bees, but it is something that has to be done in relation to a baseline,” Ascher says, “We are trying to establish that baseline. We cannot really interpret abundance until we understand the species wealth and geographical models “.
Although some of these models had been hypothesized by previous researchers such as Charles Michener, they were difficult to prove due to inaccurate, incomplete or difficult to access data. The “cleansing” of this data was a major obstacle for the researchers.
“I was surprised at how terrifying most of the previous global data on bee diversity was,” says Alice Hughes (@AliceCHughes), associate professor of conservation biology at Xishuangbanna Tropical Botanical Garden, Chinese Academy of Sciences, and another. author of the article. “A lot of the data was simply too fragmented or too focused on a small number of countries that prioritized data sharing to be able to use these resources for any large-scale analysis.”
While much remains to be learned about what drives bee diversity, the research team hopes their work will help in the conservation of bees as global pollinators.
“Many crops, especially in developing countries, depend on native bee species, not honey bees,” says Hughes. “There is hardly enough data out there on them, and providing a reasonable basis and analyzing it sensibly is essential if we are to maintain both the biodiversity and the services these species provide in the future.”
The authors see this research as an important first step towards a more comprehensive understanding of global bee diversity and an important reference basis for more detailed future bee research.
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