By genotyping individual pollen grains on a stigma, we measured pollen acquisition and donation using F2 hybrids between daylily (Hemerocallis fulva) and nightlily (H. citrina).

H. fulva, pollinated by butterflies, has diurnal, reddish flowers without scent and H. citrina, pollinated by hawkmoths, has nocturnal, yellowish flowers with a sweet scent. We place 24 and 12 pots of H. fulva and F2 hybrids in the field, and recorded visits of swallowtail butterflies and nocturnal hawkmoths to experimental plants with measured flower color, scent strength and morphological traits. We collected stigmas from flowers visited by a butterfly or a hawkmoth after every trip bout and then replaced those plants with new ones. We counted and genotyped pollen grains on collected stigmas using 10 microsatellite makers, determined the donors of deposited pollen grains and estimated outcross pollen acquisition and donation.

In both butterfly and hawkmoth pollination, reddish flowers acquired more frequent visits, and donated more pollen grains to others. These results showed that both butterflies and hawkmoths mediated selection on reddish color if nectar is available both in reddish and yellowish flowers.