The study, published in Nature Communications, examined heat tolerance in 95 native bee species found across eastern mainland Australia, spanning locations from the tropical north to the cooler southern regions.

A team of researchers from Macquarie University, The University of Sydney, La Trobe University, Flinders University, University of Wollongong, Adelaide University, and The University of Queensland explored how heat tolerance has evolved in different bee species and assessed how vulnerable they may be to a warming climate.

How Nesting Habits Affect Heat Exposure

Australia is home to about 1,700 native bee species, and these insects generally fall into three nesting categories. Some create burrows in the ground, others use cavities in wood such as tree hollows or fallen branches, and some nest inside plant stems or small existing holes in twigs.

"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, particularly species that live in thin plant stems that offer very little insulation from the heat outside," says lead author Dr. Carmen da Silva, a Research Fellow in the Pollinator Futures Research Centre at Macquarie University in Sydney.

"Stem-nesting species appear to have the lowest capacity to escape unfavorable environmental temperatures and are likely to be the most impacted by anthropogenic climate change in the near term."

The findings indicate that nesting location can play a major role in determining how well different bee species cope with rising temperatures.

Why Bee Survival Matters

According to Dr. da Silva, protecting bees is important because of the essential role they play in both natural ecosystems and agriculture.

"Bees are critical in ecosystems all over the world because of their role as pollinators, and they're under threat from warming and drying climates," says Dr. da Silva. "Bees sustain native ecosystems and play a crucial role in agricultural crop production -- tropical native bees are vital pollinators for crops like macadamia nuts, avocados, mangos, and lychees."

Tropical Bees Face Greater Climate Risks

The researchers also identified a pattern linked to geography. Bee species living closer to the equator appeared more vulnerable to climate change, with tropical bees facing the highest overall risk.

Dr. Vanessa Kellermann, Senior Lecturer in the Department of Ecology, Plant and Animal Sciences at La Trobe University and a senior author of the study, says the results highlight the complexity of predicting which species will be most affected by global warming.

"Predicting which species will be vulnerable to climate change is one of the biggest challenges in ecology," says Dr. Kellermann. "We found bee species with the highest heat tolerance were not necessarily the safest from warming, because many of them already live in extremely hot environments."

In other words, even species adapted to high temperatures may have little room left to cope with additional warming.

Understanding Native Bee Behavior

The researchers say much remains unknown about Australia's diverse native bee populations, making studies like this increasingly important.

"We still know so little about most of Australia's amazing native bees," says co-senior author Dr. Ros Gloag, Senior Lecturer in Evolutionary Biology in the School of Life and Environmental Sciences at the University of Sydney. "This study helps us recognise that having a better understanding of native bee behavior is key to identifying the greatest threats to their wild populations."