Influence of the Type of Pollen Diet on the Survival, Body Weight, and Expression of Immune-Response Genes of the Honeybee Subspecies (Apis mellifera scutellata)

Abstract

The honeybee species, Apis mellifera, is recognized globally for its essential pollination services to plants. Plants, in turn, reward bees nutritionally through nectar and pollen. Pollen is vital for development of larvae and young worker bees. Honeybees forage on polyfloral pollen rather than monofloral pollen to satisfy their dietary needs. Increased land use and land cover changes, in sub-Saharan Africa, is reducing polyfloral pollen habitats towards monocultures or few floral habitats. The effect of these two pollen types on Apis mellifera scutellata, the predominant honeybee subspecies, in Kenya is poorly understood. Yet this knowledge is critical because poor diet for bees implies a decreased quantity of hive products and reduced income for beekeepers. To fill this knowledge gap, caged bees were fed with two pollen diets (i) lowly diverse (LD), monofloral pollen (ii) highly diverse (HD), polyfloral diet and their effects on four parameters, namely survival, pollen consumption, body weight, and immune response was tested. HD-fed bees had significantly higher survival (p=0.001) and greater pollen consumption (14 mg) than LD-fed bees (11.5 mg). However, LD-fed bees (101.7 mg) were heavier than HD-fed bees (109.5 mg). The correlation between pollen consumption and body weight gain was expressed strongly (r=0.9) in HD-fed bees than in LD-fed bees (r=0.7). Overall, this study reveals the benefits that the highly diverse diets provide to honeybee workers and how pollen diversity influences honeybee life-history traits. This informs the need for conserving the biodiversity of environments for safeguarding the health of the honeybees and other pollinators.