Blueberry floral morphology influences pollinator visitation and behavioural patterns

The blueberry is a globally important fruit crop with growing demand that depends on insect pollinators for market-quality fruits. However, pollination is far from a simple process and is affected by several interacting factors. Among these, flower morphology plays a key role in determining which visitors are pollinators, the visitation rates and the occurrence of nectar robbing. In this study, we seek to identify the main pollinators for several blueberry cultivars, and relate insect floral visitors and visitation rates to flower morphology. To this end, we conducted a study in an experimental field in the Centro region of Portugal, with 19 blueberry cultivars growing under the same conditions. Flower visitors were observed, and their identity and the number of flowers visited were recorded in 5 min periods distributed throughout the day. Flower morphological traits related to pollination were measured using 6–10 flowers per individual bush. Analysis of flower morphological traits reveals variation among cultivars. Data also indicate that flower morphology influences the behaviour of insect visitors. We found three main visitors: Apis mellifera, which tended to visit cultivars with smaller flowers; Anthophora plumipes, which tended to visit cultivars with larger flowers; and Bombus terrestris, which visited cultivars with intermediate-sized flowers. Overall, our findings indicate that cultivar flower morphology and pollinator proboscis size are important in blueberry pollination, and corolla size variation should be considered in the selection of cultivars for field design. Selecting cultivars that best suit local pollination services and pollination management strategy (managed pollinators or a natural pollinator community) is key to improving production.