Difference in pollen specialisation in spring bees Andrena vaga (Andrenidae) and Colletes cunicularius (Colletidae) during their nesting season
Abstrakt
Andrena vaga and Colletes cunicularius are solitary bees distributed in Europe in regions with sandy substrate. They both nest in large aggregations and often together.
Both species occur in early spring and collect pollen usually from willows (Salix). We studied the pollen loads carried into nests by females of both species during the whole nesting season in one locality (Lazne Bohdanec, Czech Republic).
Additional material was collected in 24 other localities but usually not during the whole nesting season. The results showed that Andrena vaga is monolectic on Salix but C. cunicularius collected 11 pollen types, and one type usually dominated in each pollen load.
The pollen of Salix represented 60% or more, especially in the second half of the nesting season, when was collected less frequently. Although C. cunicularius is certainly polylectic, individual specialisation to one pollen type was revealed during foraging bouts.
The pollen diet of C. cunicularius partly corresponded with other polylectic bees in the studied locality. The main difference was pollen of Taraxacum (Cichorioideae), which was the most represented pollen type in pollen loads of polylectic bees but nearly absent in pollen loads of C. cunicularius.
Andrena vaga is probably behaviourally specialised on pollen collected on Salix only and is unable to collect pollen from flowers of other plants, contrary to C. cunicularius.