Honey bee and native solitary bee foraging behavior in a crop with dimorphic parental lines.

Insect pollination is issential for hybrid seed production systems, among which, introduced and native bees are the primary pollinating agents transferring pollen from male fertile (MF) to male sterile (MS) lines. On a highly dimorphic sunflower (Helianthus annuus) crop, we assessed the foraging behavior of solitary Melissodes bees and honey bees Apis mellifera. We found that Melissodes spp. were dominant in and showed fidelity to MF plants, gathering sunflower pollen efficiently throughout the day. In contrast, honey bees dominated on MS lines, mostly gathered nectar and exhibited high floral constancy, even after interacting with a second visitor. Also, honey bees carried sunflower pollen on their bodies while visiting MS inflorescences. This study highlights the need for a thorough understanding of the factors involved in a pollinator-dependent agroecosystem crop to assess the contribution of native bees on pollination of crops which offer resources spatially separated in two highly dimorphic parental lines.