What drives bee foraging decisions?
And how can we better detect plant-pollinator interactions?
Pollen metabarcoding to quantify plant-bee interactions
Historically, bee foraging has either been 1) observed from bee visitations to flowers, or 2) derived from microscopic identification of pollen collected from individual bee’s bodies or nests. Instead, my collaborators and I have been championing the use of amplicon sequencing to identify bee-collected pollen and reconstruct bee foraging. Our molecular approach has improved efficiency, resolution, and throughput compared to traditional pollen identification (Bell, Turo, et al. 2022). There is also great potential to apply metabarcoding tools to understand global change.
Moving beyond observational data
Metabarcoding of bee-collected pollen can reveal longer bouts of foraging and avoid many sampling biases.
Pollen preference versus pollen use
Bees make foraging choices based on floral availability and their own nutritional needs (Vaudo et al. 2020). We assume that if bees are frequently feeding on a plant— they probably like its pollen! However, bees also forage on plants simply because they’re abundant in the environment.
Does frequency of pollen collection scale with availability of pollen? Which forest plants are used in proportion to their abundance and which are preferred pollen sources?
We are using pollen DNA to examine forest bees’ pollen preferences across deciduous forests in the Northeast United States. We have regional field collections occurring from New Jersey through Maine. We expect that some non-native plants, like garlic mustard, are frequently used because they are the dominant pollen available while other plants, like black cherry, may show a signal of pollen preference.
Andrena bisalicis on Garlic mustard
Non-native herbs may be frequently foraged on by bees, but are these plants sought out as pollen sources or are they the only understory herbs available because of deer pressure?
(C) Max McCarthy PhD student in the Winfree Laboratory
Nest provisioning in the urban landscape
Most bees can forage on many different flowers (polylectic) and bee diet breadth is highly context-dependent (Cusser et al. 2019).
So what effect do local floral resources and landscape permeability have on urban bee diet breadth? Does bee identity or greenspace design drive nest provisioning?
To answer these questions, we trap-nested bees in urban greenspaces in Cleveland, Ohio and examined their pollen provisions with DNA metabarcoding (Turo et al. in review). So far, we’ve discerned that: (1) diet breadth is influenced by both bee species identity and greenspace connectivity at a landscape scale; (2) urban bees forage on both weeds and native plants.
