Heterostylous morph differences in pollen transfer and deposition patterns in Primula sieboldii on a visitation by a queen bumblebee, measured with a semi-natural experimental system

Abstract Under a semi-natural setting the between-morph pollen exchange patterns were studied in distylous Primula sieboldii flowers by measuring pollen removal from the anthers on a single visit by a Bombus diversus tersatus queen, and stigmatic pollen deposition along the sequence of the visitation of the opposite-morph flowers by the bee. Despite the twofold larger number of pollen grains produced in a single flower of the long-styled morph compared to that of the short-styled morph, no significant difference in pollen removal from a flower was found between the morphs. The stigmas of the long-styled morph received significantly more opposite-morph pollen grains than those of the short-styled morph on a single visit by the bee. Sufficient legitimate pollen grains, surpassing the ovule number, were loaded on the stigmas of 27% and 17% of visited flowers of the long- and short-styled morphs, respectively. The short-styled morph could more efficiently donate pollen to the opposite morph stigmas than the long-styled morph.