Abstract
Pollen metabarcoding is emerging as a powerful tool for ecological research and offers unprecedented scale in citizen science projects for environmental monitoring via honey bees. Biases in metabarcoding can be introduced at any stage of sample processing and preservation is at the forefront of the pipeline. While in metabarcoding studies pollen has been preserved at - 20°C (FRZ), this is not the best method for citizen scientists. Herein, we compared this method with ethanol (EtOH), silica gel (SG) and room temperature (RT) for preservation of pollen collected from hives in Austria and Denmark. After ~ 4months of storage, DNAs were extracted with a food kit, and their quality and concentration measured. Most DNA extracts exhibited 260/280 absorbance ratios close to the optimal 1.8, with RT samples from Austria performing slightly worse than FRZ and SG samples (P < 0.027). Statistical differences were also detected for DNA concentration, with EtOH samples producing lower yields than RT and FRZ samples in both countries and SG in Austria (P < 0.042). Yet, qualitative and quantitative assessments of floral composition obtained using high-throughput sequencing with the ITS2 barcode gave non-significant effects of preservation methods on richness, relative abundance and Shannon diversity, in both countries. While freezing and ethanol are commonly employed for archiving tissue for molecular applications, desiccation is cheaper and easier to use regarding both storage and transportation. Since SG is less dependent on ambient humidity and less prone to contamination than RT, we recommend SG for preserving pollen for metabarcoding. SG is straightforward for laymen to use and hence robust for widespread application in citizen science studies.
Highlights
Pollen collected by honey bees (Apis mellifera L.), and further sampled from hives equipped with pollen traps, is frequently investigated in order to understand the floral environment (Bilisik et al, 2008; Danner et al, 2017; Drummond et al, 2018; Jones et al, 2021; Requier et al, 2015; Tosi et al, 2018)
This was lower than the water content obtained for pollen dried at room temperature (RT) (14.8%) and almost half of the value obtained with 1 g of silica gel (SG) (18.0%) for the same period
While pollen metabarcoding studies have typically worked with samples preserved at − 20 °C, this is the first study to examine how different preservation methods affect molecular identification of mixed pollen samples by high-throughput sequencing
Summary
Pollen collected by honey bees (Apis mellifera L.), and further sampled from hives equipped with pollen traps, is frequently investigated in order to understand the floral environment (Bilisik et al, 2008; Danner et al, 2017; Drummond et al, 2018; Jones et al, 2021; Requier et al, 2015; Tosi et al, 2018). Numerous studies have sought to gain a broader understanding on honey bee biology and health by examining botanical diversity of pollen loads transported by foragers into the colony (Avni et al, 2014; Danner et al, 2016; Di Pasquale et al, 2013; Smart et al, 2016). This goal has been addressed by identifying honey bee–collected pollen loads through visual inspection of the grains’ exine under a light microscope. Because this method is time consuming, Environ Monit Assess (2021) 193:785 labour intensive, expert-knowledge dependent and frequently lacks taxonomic resolution, it is gradually being replaced by alternative approaches (Dunker et al, 2021) of which DNA metabarcoding is gaining increasing popularity (e.g. Bell et al, 2017; Cornman et al, 2015; Danner et al, 2017; Jones et al, 2021; Keller et al, 2015; Macgregor et al, 2019; Potter et al, 2019; Richardson et al, 2019; Smart et al, 2016)
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
