# Increasing temperatures affect thoracic muscle performance in Arctic bumblebees

## TL;DR

Rising temperatures threaten Arctic bumblebees by affecting their non-flight muscle performance, which could disrupt pollination and communication.

## Contribution

The study reveals how increasing temperatures impact non-flight thoracic muscle performance in Arctic bumblebees, a previously unexplored area.

## Key findings

- Thorax acceleration during defensive buzzing peaks at 25 °C and declines afterward to prevent overheating.
- Vibration frequency increases with temperature and is better explained by thorax temperature than air temperature.
- Thermal responses of non-flight vibrations are consistent across species, castes, and temperature habitat specializations.

## Abstract

Increasing temperature beyond a species’ optimum is a major threat to insect biodiversity, particularly in rapidly warming regions such as the Arctic. For cold-adapted pollinators, high temperatures can disrupt physiology and ecosystem services, threatening pollinator populations and plant reproduction. In bumblebees, increased temperature disrupts the physiology of the indirect flight muscles. However, these muscles, which generate the bee’s charismatic buzz, also facilitate key non-flight behaviours including communication, defence, and buzz-pollination, where temperature effects remain unexplored. Here, we assess the thermal performance of non-flight muscle function across 15 Arctic bumblebee species by measuring thorax vibrations during defensive buzzing behaviour. Thorax acceleration is found to peak at an air temperature of 25 °C, declining after this peak as a potential strategy to prevent overheating. Conversely, vibration frequency continues to increase with temperature, and is better explained by thorax temperature than air temperature. Surprisingly, there are no differences in thermal response across species, castes, or temperature habitat specialisations, indicating that non-flight vibrations are similarly susceptible to unfavourable temperatures across bumblebee species. If such findings translate to non-flight buzzing in other contexts, such as buzz-pollination, changes in buzzes have the potential to disrupt key plant-pollinator interactions.

Increasing temperatures threaten cold-adapted pollinators such as Arctic bumblebees by disrupting their physiology. This study found that thorax acceleration during non-flight vibrations peaks at 25 °C for these bumblebees, while vibration frequency continues to increase with temperature.