Neotropical stingless bees display a strong response in cold tolerance with changes in elevation.

Area of Science:

• Ecology and Evolutionary Biology
• Climate Change Biology
• Insect Physiology

Background:

• Tropical pollinators face climate change threats, yet their thermal biology is poorly understood.
• Stingless bees are crucial ecologically, economically, and culturally in tropical ecosystems.
• Understanding thermal tolerance is vital for predicting species' responses to environmental shifts.

Purpose of the Study:

• To assess the thermal tolerance (lower and upper critical limits) of stingless bees across Andean elevations.
• To investigate how body size, hairiness, and coloration affect thermal limits.
• To explore nest thermoregulation strategies in response to varying climates and potential social adaptations.

Main Methods:

• Measured critical thermal minimum (CTMin) and maximum (CTMax) for 17 stingless bee species at 200m and 1500m.
• Correlated thermal limits with intertegular distance (body size), thoracic hair length, and lightness.
• Monitored brood nest temperature and humidity in three species at both elevations over several weeks.

Main Results:

• CTMin decreased with elevation, while CTMax remained similar across elevations.
• Larger body size, longer hair, and lighter coloration weakly correlated with higher CTMin and CTMax.
• Brood nests showed greater temperature fluctuations at low elevation but stable, higher temperatures at high elevation; humidity was consistent.

Conclusions:

• Stingless bees exhibit differential thermal sensitivities and potential local adaptations to climate, supporting elevation-specific conservation.
• Brett's heat-invariant hypothesis may explain observed CTMax patterns.
• Nest thermoregulation is flexible and varies with elevation, highlighting adaptive capacity.