Pollen-borne microbes shape bee fitness.

Area of Science:

• Ecology
• Microbiology
• Entomology

Background:

• Diverse symbiotic microbes inhabit bee pollen, offering benefits to bees.
• These microbes may constitute a significant dietary resource for developing bee larvae.
• Evidence linking pollen-borne microbes to larval health is currently limited.

Purpose of the Study:

• To investigate the effects of microbe-deficient diets on the fitness of larval mason bees.
• To determine the nutritional contribution of pollen-borne microbes to bee larvae.
• To assess the impact of microbial deprivation on larval growth, biomass, and survival.

Main Methods:

• Larval mason bees were fed diets with varying fractions of sterilized, microbe-deficient pollen.
• Amino acid and fatty acid trophic biomarker analyses were employed.
• Larval growth rates, biomass, and survivorship were measured.

Main Results:

• Trophic biomarker analyses indicated larvae derived substantial nutrition from microbial prey, occupying a higher trophic position than herbivores.
• Larvae on increasingly sterile diets showed significant adverse effects on growth, biomass, and survivorship.
• Complete deprivation of pollen-borne microbes led to a marked decline in larval fitness.

Conclusions:

• Microbes associated with aged pollen are essential for bee health, acting as both nutritional mutualists and a major dietary component.
• The conservation of bee-microbe interactions is vital for pollinator protection, especially amid global bee decline.
• These findings highlight the critical role of symbiotic microbes in sustaining bee populations.