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

Abstract

It is increasingly recognised that intraspecific variation in traits, such as morphology, behaviour, or diet is both ubiquitous and ecologically important. While many species of predators and herbivores are known to display high levels of between-individual diet variation, there is a lack of studies on pollinators. It is important to fill in this gap because individual-level specialisation of flower-visiting insects is expected to affect their efficiency as pollinators with consequences for plant reproduction. Accordingly, the aim of our study was to quantify the level of individual-level specialisation and foraging preferences, as well as interspecific resource partitioning, in three co-occurring species of bees of the genus Ceratina (Hymenoptera: Apidae: Xylocopinae), C. chalybea, C. nigrolabiata, and C. cucurbitina. We conducted a field experiment where we provided artificial nesting opportunities for the bees and combined a short-term mark-recapture study with the dissection of the bees’ nests to obtain repeated samples from individual foraging females and complete pollen provisions from their nests. We used DNA metabarcoding based on the ITS2 locus to identify the composition of the pollen samples. We found that the composition of pollen carried on the bodies of female bees and stored in the brood provisions in their nests significantly differed among the three co-occurring species. At the intraspecific level, individual females consistently differed in their level of specialisation and in the composition of pollen carried on their bodies and stored in their nests. We also demonstrate that higher generalisation at the species level stemmed from larger among-individual variation in diets, as observed in other types of consumers, such as predators. Our study thus reveals how specialisation and foraging preferences of bees change from the scale of individual foraging bouts to complete pollen provisions accumulated in their nests over many days. Such a multi-scale view of foraging behaviour is necessary to improve our understanding of the functioning of plant-flower visitor communities.

The value of twinned pollinator-pollen metabarcoding: bumblebee pollination service is weakly partitioned within a UK grassland community

“…CO1 DNA barcoding has potential to improve the species identification of bees for field-based studies of foraging behaviour 30 , resource partitioning 31 and ecology 32 , but first requires that species assignment is not compromised by excessive intraspecific variation within the study location. Phylogenetic trees presented in the present study included sufficient reference barcodes of the 24 UK bumblebee species to provide context for both intra- and inter-specific variation of the CO1 locus in the study area.…”

More than mesolectic: Characterizing the nutritional niche of Osmia cornifrons

“…This may indicate that there is a larger degree in dietary variability than previously observed for O. cornifrons. Indeed,Klečka et al (2022) andGaiarsa et al (2022) demonstrated that generalist bee species in genus Ceratina are composed of many specialist individuals, and with more advanced DNA metabarcoding technology to track plant-pollinator interactions, future studies can glean more insight into individual variation within a species.…”