Cold Tolerance Differences Between Declining Native and Invasive Bumblebees in Patagonia.

Area of Science:

• Ecology
• Evolutionary Biology
• Zoology

Background:

• Temperature significantly influences insect establishment and spread.
• Thermal tolerance differences can explain geographical distribution and invasion success.
• The native bumblebee Bombus dahlbomii is being displaced by the invasive Bombus terrestris in Patagonia.

Purpose of the Study:

• Investigate the role of cold tolerance in the displacement of B. dahlbomii by B. terrestris.
• Determine if cold tolerance differences correlate with the species' geographical distribution.
• Explore potential mechanisms underlying cold tolerance in both bumblebee species.

Main Methods:

• Assessed minimum temperatures across the South American distribution of both species.
• Measured chill coma onset and recovery temperatures to quantify cold tolerance.
• Examined morphological traits (body size, hair length) as potential adaptations to cold.

Main Results:

• Both species encounter similar minimum temperatures in their ranges.
• B. dahlbomii exhibits superior cold tolerance, entering chill coma at lower temperatures and recovering faster than B. terrestris.
• Larger body size and longer hairs in B. dahlbomii may aid in heat conservation but do not confer a foraging advantage in Patagonia.

Conclusions:

• Cold tolerance alone does not explain the dominance of the invasive B. terrestris in Patagonia.
• Native B. dahlbomii possesses greater physiological and morphological adaptations to cold environments.
• The success of B. terrestris is likely attributed to other factors such as heat tolerance, disease resistance, or life history traits.