Thermal tolerance in the cellophane bee Colletes inaequalis reflects early spring adaptation and is independent of body size and sex

Authors: GONZALEZ, VICTOR - University Of Kansas; HERBISON, NATALIE - University Of Kansas; HERRERA, ANDRES - University Of Kansas; Oyen, Kennan; SMITH, DEBORAH - University Of Kansas

Submitted to: Ecology and Evolution
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 8/4/2025
Publication Date: 8/12/2025
Citation: Gonzalez, V.H., Herbison, N., Herrera, A., Oyen, K.J., Smith, D.R. 2025. Thermal tolerance in the cellophane bee Colletes inaequalis reflects early spring adaptation and is independent of body size and sex . Ecology and Evolution. 15(8). Article e71983. https://doi.org/10.1002/ece3.71983.
DOI: https://doi.org/10.1002/ece3.71983

Interpretive Summary: Pollinators are critical for maintaining agricultural resources. We compared the impact of temperature variation two native American pollinators. We found that pollinators which emerge earlier in spring tend to tolerate colder temperatures than those that emerge later in the summer, suggesting that the temperature tolerance of native pollinators tend to align with their seasonal activity.

Technical Abstract: 1. Colletes inaequalis Say is a univoltine, ground-nesting solitary bee and one of the first pollinators to emerge in North American springtime. As in most solitary bees, males emerge first and are smaller than females. 2. Despite its role as pollinator of early spring wild plants and crops, the thermal ecology of C. inaequalis remains largely unexplored. 3. We assessed the lower (CTMin) and upper (CTMax) critical thermal limits and chill coma recovery time, testing the effects of sex and body size (fresh body mass and intertegular distance, ITD). We compared C. inaequalis with the European honey bee, a similarly sized species active in early spring, and examined how cold exposure duration, repeated cold stress, and starvation affect chill coma recovery in C. inaequalis males. 4. We found that males and females of C. inaequalis exhibit similar thermal limits, and neither CTMin nor CTMax increased with ITD. Fresh body mass did not affect chill coma recovery time. Colletes inaequalis was significantly more cold-tolerant but less heat-tolerant than honey bees, recovering much faster from chill coma. Repeated cold stress significantly impacted recovery time, while food was the primary factor influencing mortality in C. inaequalis males. 5. These findings suggest C. inaequalis is physiologically adapted to early spring conditions, whereas honey bees rely more on social and behavioral mechanisms to cope with low temperatures. These results suggest that bee communities, on average, may exhibit thermal tolerances that align with their seasonal activity periods.