Bee species that nest in plant stems appear to be at the greatest short-term risk from increasing temperatures due to climate change, while those that nest in the ground are more able to evade extreme heat, according to new research from Australian evolutionary ecologists.
The study, published today in the international journal Nature Communications ( link ), assessed heat tolerance in 95 different native bee species in eastern mainland Australia, at all latitudes from north to south.
Researchers from Macquarie University, The University of Sydney, La Trobe University, Flinders University, University of Wollongong, Adelaide University and The University of Queensland investigated the way tolerance to heat has evolved across diverse bee species and compared their sensitivity to climate change.
Australian native bees – of which there are some 1700 species – have three main nesting behaviours: some nest in burrows in the ground, some in wood cavities like tree hollows or fallen dead branches, and others in plant stems or existing holes in small 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 unfavourable environmental temperatures and are likely to be the most impacted by anthropogenic climate change in the near term."
"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."
Dr Vanessa Kellermann, Senior Lecturer in the Department of Ecology, Plant and Animal Sciences at La Trobe University, says the research also found a clear trend for increasing vulnerability to climate change closer to the equator, with tropical bees at the greatest risk.
"Predicting which species will be vulnerable to climate change is one of the biggest challenges in ecology," says Dr Kellermann, a senior author of the study. "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."
"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 behaviour is key to identifying the greatest threats to their wild populations."
