COS 305-4 - Evaluating effect of formic acid treatment on foraging behaviors of Apis mellifera through pollen DNA metabarcoding using the MinION device

Abstract: Bees play a vital role in maintaining the health and productivity of terrestrial ecosystems by providing pollination to many of the world’s plants. In recent decades, many bee species, including Apis mellifera (European honeybee), have experienced worldwide population declines. Varroa destructor, an external parasite, is one of the leading causes of honeybee population declines, as they are the primary cause of colony collapse disorder.

Various methods exist to control the impact of V. destructor, including Formic Acid (FA) treatment, a well-documented solution to reducing V. destructor numbers. Yet, despite clearly established evidence that A. mellifera behaviors are very sensitive to changes in their hive environment, very few studies have looked at the effect of FA on honeybee foraging behavior. DNA metabarcoding is a powerful tool allowing ecologists to quantitatively assess differences in diet within species without the need of an extensive knowledge of pollen taxonomy or complicated fieldwork experiments.

In this study, A. mellifera hives (n=7) were split into control (n=3) and treatment groups (n=4). Pollen samples were collected from all hives before, during, and after FA treatment to compare if FA application impacted the foraging patterns of the bees in the treated colonies as compared to the control group. To compare foraging patterns between the treatments, we performed metabarcoding using the trnL (UAA) chloroplast intronic region, commonly used to barcode plant species. Amplicons were subsequently sequenced with a portable sequencer (ONT MinION Mk1C). Basecalling, quality check, demultiplexing, and filtering of the data were conducted with Guppy and Medaka. Obtained sequences (n=120 reads) were compared to a reference database with BLAST in order to determine sequence identity of visited plants.

With this information we compared absolute foraging numbers, species, and related ratios between control and experimental hives. Most sequences were assigned with high percentage identity to a sample database ( >89%), and we were able to accurately identify 10 visited plant species. Although certain species (e.g., Malus sylvestris [European crab apple] and Prunus avium [wild cherry]) were probably visited by all hives, our preliminary findings show that pollen loads differ between control and experimental conditions, indicating a variation in floral visitation.

These results suggest that FA treatment, while effective at controlling V. destructor, may impact honeybee foraging patterns. Further research is needed to understand if this behavioral change is detrimental to the health of the colony, and the consequences of variation in floral visitation to pollination networks.