Against the odds: Nesting specialization and foraging ecology provide insights into climate change responses in a mountain bee

Abstract Climate change is rapidly altering temperature regimes in mountain environments, reshaping the distribution and activity of pollinators. Studies of insect pollinator assemblages in mountains show a general pattern of decreasing bee (Anthophila) activity with increasing elevation. Here we report a unique Exoneura bee, that counters this trend and thrives in cold, high‐elevation (~1500–1900 m a.s.l.) woodlands at the tree line. While other members of the genus at lower elevations nest in narrow pithy or hollow plant stems, this bee has a unique nesting biology, burrowing into the dead branches of the only tree in Australia's subalpine zone (snow gum, Eucalyptus pauciflora subsp. niphophila ). Using a combination of observational surveys, spatial mapping, temperature tolerance tests and biophysical modelling, we investigated various aspects of the bee's ecology. We found that this species' nest abundance peaked at the tree line (approx. 1900 m m a.s.l). Foraging behaviour was highly dependent on the presence of snow gums for nesting, with activity concentrated within 30 m of snow gum stands. Biophysical modelling showed that the daily and annual foraging activity window was significantly limited by temperature and that it will substantially increase under climate change projections. This study reveals several unique traits of a new bee species that show a close association with snow gums, providing insights into its flourishing in the changing conditions of subalpine Australia's high‐elevation environments.