Richard Musgrove
Dr Richard Musgrove is a zoologist and science journalist. He writes for Cosmos and Double Helix.
Feral European honeybees are outcompeting Australian native bees, reducing their fitness and number of offspring, forcing native bees into decline.
“We need to manage honeybee densities carefully, especially in areas of high conservation value or where native pollinators are already under pressure from factors such as growing urbanisation,” says native bee entomologist, Dr Kit Prendergast, of Curtin University.
About 2200 native bee species range around Australia, many of which are important pollinators of Australia’s unique flora. “Around five hundred of these are yet to be described,” says Prendergast.
There’s such a diversity, she says. “Some of them are solitary but don’t take care of their young; some share a nest entrance, but have their own little burrows within the nest. Some share a nest and rearing of offspring. Then you’ve got the sugar bag bees that make honey, like a European honeybee, with a queen, the workers and a colony.”
Nests can be lined with leaf or flower discs, and partitioned with a cellophane- or resin-like secretion. Then there’s the resin-pot bees, the Megachile, she adds.
New native bees are regularly discovered — 71 new resin pot bee species were announced this month by a team led by entomologists from the University of Adelaide.
“Despite their environmental and economic importance as pollinators of native plants and crops, the Australian bee fauna is poorly understood,” says Dr Katja Hogendoorn, of the University of Adelaide who co-authored the study published in the Australian Journal of Taxonomy.
“An estimated one-third of bee species remains unknown to science, and a dearth of funding for taxonomic work hampers our ability to assess the conservation status and undertake action to protect native bees.
“We may be losing species that we don’t even know about yet.”
The introduction of exotic European honeybees (Apis mellifera) in the 1820’s has had an under-appreciated impact on native bees. Forced to share pollen resources with a much more numerous competitor, the natives have struggled, with less food meaning lower reproductive rates, skewed sex ratios and reduced populations within this vital insect group, says Prendergast.
“European honeybees are livestock”, she told Cosmos. “Like cattle or chickens”
“They’re used to produce honey and for crop pollination but they’re not part of the environment. If they’re out in the wild, they’re a feral species.”
European honeybees are often portrayed as a symbol of the environment, which is like saying cattle represent native Australian grazers or chickens represent bird diversity, she says. “They’re a managed livestock species, and when they’re in the environment, they can cause harm through competition with native bees and with other nectar-feeding animals, like honey eaters.”
To explore impacts of honeybee numbers on native bee health and reproduction, Prendergast set up especially-designed ‘bee hotels’ in 14 urban bushland and garden sites in Perth, Western Australia.
The study, published in Frontiers of Bee Science, also included researchers from University of Southern Queensland; the University of Western Australia; the University of Guelph in Canada; and the Chinese Academy of Sciences.
“Bee hotels are more than just a way to give bees a place to nest – they’re powerful research tools that let us measure how well native bees are surviving and reproducing in different environments,” Dr Prendergast says.
“We also studied 1000 native bee nests which provided valuable insights into the fitness of at least 25 species,” she says.
Bee hotels and nests were monitored over two Spring to Summer bee seasons.
“In areas with higher honeybee densities, native bees produced fewer female offspring, had higher offspring mortality and the males that did emerge were smaller – all of which are signs of reduced fitness.”
Honeybees were also foraging from a wider range of flowers than the native species
“In some conditions, greater overlap in pollen use was associated with lower offspring numbers in native bees.”
Feral honeybees were significantly reducing the pollen available to the native bees.
“Honeybees are superior competitors, because there’s just so many of them, and they can also recruit their nest mates to the best resources,” says Prendergast.
They take so much pollen that female native bees don’t have enough, which means fewer offspring per nest, or maybe not as much food per offspring, so the larvae are more likely to die.”
Offspring body size is also tied to food supply.
“Under limited resources, females will also often produce more males, because male bees are smaller and they’re produced from unfertilized eggs,” says Prendergast.
Females can choose the sex of their offspring in Hymenoptera (the order that includes bees, wasps, sawflies and ants).
Dr Kit Prendergast, who goes by the social media title “The Bee Babette.” (image John Cobbett)
“In the short term this works because it means they can still reproduce, but in the long term, fewer females are produced, leading to a male-biassed population. That can lead to declines, and reduce genetic diversity as well.
“This shows that honey bees are not as benign as some might think – they can negatively impact local ecosystems and potentially contribute to declines in native bee populations.”
“If we want to conserve native bees, and conserve biodiversity as a whole, it can’t all be about what’s the economic return for humans, because that’s why we’re having a biodiversity crisis. Anything that doesn’t contribute to economics or food or industry tends to be, well, we don’t need to worry about it then. I feel like it’s a very egotistical perspective.”
Inside the mind of the honeybees
