Warm Temperatures Reduce Flower Attractiveness and Bumblebee Foraging.

Area of Science:

• Plant biology
• Ecology
• Climate change research

Background:

• Plants use visual signals like size and color to attract pollinators.
• Floral signals and rewards can be altered by environmental stresses such as increased temperature.
• Rising global temperatures may impact plant-pollinator interactions.

Purpose of the Study:

• To investigate how pollinators respond to changes in floral signals and rewards under warmer temperatures.
• To determine the effects of increased temperature on starflower (Borago officinalis) and its pollinator, the buff-tailed bumblebee (Bombus terrestris).

Main Methods:

• Cultivated starflowers at 21 °C and 26 °C, measuring visual traits and rewards (nectar, pollen).
• Observed bumblebee behavior in a controlled flight arena using a binary choice experiment.
• Tracked insect visits to flowers from different temperature treatments.

Main Results:

• Plants at 26 °C had smaller floral areas (34.4 cm² vs 71.2 cm²) and greater flower height compared to those at 21 °C.
• Nectar production per flower was significantly lower at 26 °C (2.67 µL vs 4.15 µL).
• Bumblebees visited flowers from 26 °C plants four times less frequently than those from 21 °C plants.

Conclusions:

• Warmer temperatures negatively impact floral signals and reduce available floral resources.
• Climate change-induced temperature increases may decrease pollination rates and plant reproductive success.
• Reduced flower visitation by pollinators is a key consequence of elevated temperatures.