Bee species perform differently between sexes of a gynodioecious globose cactus

Abstract

Bee species interact differently with flowers, playing different roles in pollination. For gynodioecious plant populations, which consist of two sexes (female-non-pollen-producing flowers and hermaphroditic flowers), bee–flower interactions also have ecological implications, including the maintenance of females. We evaluated bee performance on a gynodioecious globose cactus, Coryphantha elephantidens, to determine how bees interact with different sexes and if they visit and pollinate them differently. We recorded videos of visits to both hermaphroditic and female flowers (n = 26 flowers of each sex). From these videos, we registered and analyzed bee visitation rate, handling time, and behavior using non-parametric models, generalized linear models, and chi-squared tests. Our findings revealed 15 species of visiting bees, with the most frequent being Augochlorines (59%), Ashmeadiella opuntiae (21%), and Apis mellifera (13%). Augochlorines were focused on collecting pollen and rarely touched stigmas, while A. mellifera promoted self-pollination, as they contacted stigmas after contacting the stamens. The solitary bee A. opuntiae emerged as the most effective pollinator, promoting cross-pollination by visiting both sexes with equal frequency. Since both sexes of C. elephantidens lack nectar and female flowers lack pollen, we suggest that female flowers are pollinated by deceit. This cactus species exhibits functional specialization, as only three bee species significantly contribute to pollination. Although the other remaining bees are not effective pollinators, their presence suggests this cactus is an important host for a wide variety of wild bees.