Data from Pollinator effectiveness and importance between female and male mining bee (Andrena)

Bees are often considered to be effective pollinators in both agricultural
and natural ecosystems, but could be ‘ugly’ pollinators in that they
collect large quantities of pollen for food provision but deliver little
to stigmas. Male bees do not collect pollen to feed larvae, and their
pollination role has been underappreciated. Here we compare pollination
transfer efficiency and effectiveness between female and male individuals
of a mining bee, Andrena emeishanica, visiting a nectariferous spring
flower (Epimedium pubescens). Female bees were observed to forage for both
pollen and nectar, but male bees foraged only for nectar. Female bees had
large hairy hind tibiae with conspicuous scopae, and nearly 90% of the
pollen grains they collected went onto the hind legs. Male bees removed
less pollen from anthers than female bees but deposited more pollen on
stigmas per visit. The higher pollen transfer efficiency of male bees was
due to 48.4% of pollen grains remaining ungroomed on the thorax and
abdomen, available for stigma contact, but their visitation rate to
flowers was much lower. Our results indicate that male solitary bees could
be more efficient than females (more pollen transfer per visit), but less
effective (less pollen transfer in total, because fewer visits per unit
time).