Female‐biased nectar production is associated with the Darwin's inflorescence syndrome

Abstract

• Plant reproduction is influenced not only by individual flower characteristics but alsoby the arrangement of flowers within inflorescences. In bee-pollinated plants with protandrous flowers in vertical acropetal inflorescences — where male fertile flower structures mature before female ones and basal flowers open first (i.e., Darwin’sinflorescence configuration) — male-phase flowers are positioned above female-phaseflowers. This arrangement benefits from the upward foraging motion of bees, reducingpollen transfer between flowers of the same plant and increasing pollen export. Additionally, female-biased nectar production in these species could reinforce upward beemovement, further reducing self-pollen transfer.• We conducted a comparative study of 112 hermaphrodite angiosperm species withtemporal separation of male and female reproductive functions (i.e., dichogamy) toexplore whether female-biased nectar production is common among bee-pollinatedspecies with Darwin’s inflorescence configuration.• Our results revealed female-biased nectar production in bee-pollinated species withDarwin’s inflorescence configuration. In the absence of bee pollination, species withthis type of inflorescence exhibit male-biased nectar production. Gender-biased nectarproduction is absent in species lacking this inflorescence type.• Female-biased nectar production in vertical acropetal inflorescences with protandrousflowers likely evolved independently in different bee-pollinated species to enhance pollen export. Our study emphasizes the need for microevolutionary research on how nectar production patterns adapt to bee pollination in species with Darwin’s inflorescenceconfiguration. It also calls for investigation into the developmental biases influencingnectar production in plants with dichogamous flowers.