New research shows that nesting behavior drives vulnerability to climate change – and may disrupt which species are considered most vulnerable.
(CN) – Australia’s native thin-nest bees face the greatest short-term risk from rising temperatures, even though they have evolved the highest heat tolerance among their peers, according to the authors of a comprehensive new study.
The researchers tested the maximum critical thermal temperature at which bees lose coordinated movement in 95 native bee species collected across eastern Australia, from tropical northern to cooler southern latitudes. The work, involving nearly 3,500 individual bees, shows that nest behavior shapes how these essential pollinators adapt to heat, more than just broad climate patterns.
The collaborative team from Macquarie University, University of Sydney, La Trobe University, Flinders University, University of Wollongong, University of Adelaide and University of Queensland found that sticklebacks experience hotter nesting microclimates and, despite their superior heat tolerance, end up with narrower buffers between what they can withstand and the temperatures they actually encounter.
In contrast, ground-nesting bees, which burrow into soil that prevents extreme heat, have evolved lower heat tolerances but enjoy greater protection in their cooler underground homes. In between fall the hollow nests, which burrow into the wood like tree hollows.
“Bees that nest underground can hide from extreme heat – as a result, they don’t experience temperatures as high as those that live above ground, especially species that live in thin plant stems that offer very little insulation from the heat outside,” said lead author Carmen da Silva of Macquarie University’s Pollinator Futures Research Centre, in a press release.
The study, published Monday in Nature Communicationspoints out the “Bogert effect”, where behavior such as choosing a nest site affects the strength of natural selection on physiological traits such as heat tolerance. Macroscale climate data explained little variation in heat tolerance, but inclusion of nest microclimate temperatures doubled explanatory power.
Australia is home to around 1,700 species of native bees, vital to wildlife ecosystems and crops such as macadamia, avocado, mango and lychee in tropical regions.
“Bees are critical in ecosystems around the world because of their role as pollinators, and they are under threat from a warming and drying climate,” explained da Silva. “Bees support native ecosystems and play a crucial role in the production of agricultural crops.”
The research also revealed a latitudinal gradient. Tropical bees near the equator are generally more vulnerable, as they already live closer to their thermal limits.
Senior author Vanessa Kellermann of La Trobe University noted a key nuance: “Predicting which species will be vulnerable to climate change is one of the greatest challenges in ecology,” Kellermann said. “We found that the bee species with the highest heat tolerance were not necessarily the safest from warming, because many of them already live in extremely hot environments.”
Co-author Ros Gloag from the University of Sydney highlighted the knowledge gap.
“We still know so little about most of Australia’s amazing native bees,” Gloag said. “This study helps us realize that better understanding the behavior of native bees is key to identifying the biggest threats to their wild populations.”
Importantly, the team ruled out major roles for body size or short-term adaptation to known changes in the environment in driving the patterns. They also demonstrated that ignoring nesting behavior changes the ranking of vulnerability, such that ground nests appear most vulnerable when only air temperatures are considered, but stem nests rise to the top when real nest microclimates are considered.
While all bees forage outside their nests and will feel long-term climate impacts, the authors say short-term conservation priorities should focus on stem nests, whose limited margin of error for how much heat they can withstand leaves them with the least capacity to survive adverse conditions in the coming decades.
Subscribe to our free newsletters
Our weekly newsletter Closing arguments provides the latest on ongoing trials, major litigation and decisions in courts around the US and the world, while monthly Under the lights feeds legal dirt from Hollywood, sports, Big Tech and the arts.
