Individual-level specialisation and interspecific resource partitioning in bees revealed by pollen DNA metabarcoding

Area of Science:

• Ecology
• Evolutionary Biology
• Behavioral Ecology

Background:

• Intraspecific variation in traits like diet is ecologically significant.
• High individual diet variation is known in predators and herbivores, but understudied in pollinators.
• Individual specialisation in flower-visiting insects can affect pollination efficiency and plant reproduction.

Purpose of the Study:

• To quantify individual specialisation and foraging preferences in three co-occurring bee species (Ceratina chalybea, C. nigrolabiata, C. cucurbitina).
• To assess interspecific resource partitioning among these bee species.
• To understand how specialisation varies across different scales, from individual foraging bouts to accumulated nest provisions.

Main Methods:

• Field experiment with artificial nesting opportunities for bees.
• Mark-recapture study combined with nest dissection for individual sampling.
• DNA metabarcoding (ITS2 locus) to identify pollen composition from bee bodies and nest provisions.

Main Results:

• Significant differences in pollen composition were found among the three bee species.
• Individual female bees exhibited consistent differences in diet specialisation and pollen composition.
• Species-level generalisation was driven by greater among-individual variation in diets, similar to other consumer types.

Conclusions:

• Individual foraging preferences and specialisation in bees vary significantly at both the individual and species level.
• Understanding multi-scale foraging behaviour is crucial for comprehending plant-pollinator community dynamics.
• This study highlights the importance of intraspecific variation in pollinator diets for ecosystem functioning.