For over a decade, invasive Asian honeybees have defied evolutionary expectations and established a thriving population in North Queensland, a major concern for the honey industry, biosecurity officials and our forests.
Research published in the new edition of Current Biology has shown the species Apis cerana has overcome what is known as a ‘genetic bottleneck’ to grow from a single swarm into a population of more than 10,000 colonies over a 10,000 sq km area, about the size of Greater Sydney.
Co-lead author Dr Rosalyn Gloag, lecturer in evolutionary biology at Sydney University’s School of Life and Environmental Sciences, says a study of this bee population shows that some species can quickly adjust to new environments despite starting with very low genetic diversity relative to their native-range populations.
“The high genetic diversity is generally assumed to be important for a population to quickly adapt to changing environmental conditions, such as when a species is translocated or experiences rapid environmental change caused by natural or climate change disasters,” Dr Gloag said.
“However, we have shown that this invasive population of honeybees has rapidly adapted since its arrival despite suffering a steep loss in genetic diversity.”
The honeybee industry contributes more than $2.89 billion annually to the Queensland economy. Much of the economic contribution is made through the increasing demand for honey beehives, which provide critical pollination and forest seed fertilisation.
Queensland beekeepers currently provide honeybees for professional pollination services to provide honeybees for professional pollination services to the almond, avocado, apple, berry, cherry, macadamia, melon, pear and pumpkin industries, to name a few.
The state’s honeybee industry is also well known for producing some of Australia’s finest honey from trees such as yellow box, ironbark, river red gum, blue gum and blackbutt.
More than 70% of honey produced in Queensland is derived from native forests, while professional beekeepers access apiary sites in national parks, state forests and other timber reserves through a dedicated permit system.
Pollinators abound in forests. However, scientific research has focused on bees living closer to the ground. This sampling bias is replicated across much of the world. For example, another related Oceanic masked bee, Pharohylaeus lactiferous or cloaked bee, was recently found in the forest canopy after 100 years in hiding.
Bee sampling in Fiji turned up only one bee from the genus Hylaeus. This bee probably belonged in the canopy, so scientists were fortunate to catch it near the ground. Targeted attempts over the next few years, using short insect nets, failed to find any more. But this changed when attention was turned to searching the forest canopy.
Such sampling is physically challenging; strength and skill are required to sweep a long, heavy net and pole through the treetops. It’s quite a workout with efforts limited to the edges of forests where branches won’t tangle the whole contraption. But by lifting their gaze, scientists discovered eight new bee species in the tree canopies.
Dr Gloag and her research team highlighted the importance of their case study for understanding population resilience in general.
“This is even more important as we observe many species dealing with anthropogenic climate change,” Dr Gloag said.
Studying the invasive population in Queensland gave the researchers a rare complete genetic timeline of a natural invasion, beginning soon after the bees arrived.
The arrival of the colony in 2007, likely from Papua New Guinea, worried Australian biosecurity because of the parasites the bees can carry.
Ultimately, these bees did not carry the most feared of its parasites, the varroa mite, which has since arrived in NSW by an unknown route, threatening the domestic honey industry.
“We were lucky to have a complete sample timeline of this invasive population thanks to the incredible efforts of the Queensland Department of Agriculture and Fisheries, which sampled the population extensively during the early years of the incursion as part of an eradication attempt,” Dr Gloag said.
“Although that attempt was unsuccessful, the biological material collected has been incredibly valuable for understanding how these invasions proceed. And that, in turn, helps us better prepare for future invasions,” she said.
Access to this comprehensive sample set allowed scientists to re-sequence entire genomes of 118 individual bees collected over ten years.
Dr Rosalyn Gloag added: “We could observe natural selection over time in a population that started with low genetic diversity. From this unique vantage point, we could see that selection acted on the variation in genomes that had arrived with the handful of original bees. It wasn’t variation that arose later by mutations. In other words, some species with very low genetic diversity can adapt quickly.”
While this might be bad news for environments coping with newly-arrived invasive species, it’s potentially good news for populations with temporary crashes due to climate change or other natural or human-induced disasters such as bushfires.”
The Queensland study was undertaken in collaboration with scientists at Canada’s York University, the IPB University and, the Bandung Institute of Technology in Indonesia, and CSIRO.
