New evidence that blueberry (Vaccinium spp.) has floral traits that enable pollination at night

Abstract

The role of nocturnal pollinators has been globally understudied, particularly in agriculture, but growing evidence suggests that crops often assumed to be pollinated during the day also receive additional pollination by night-active animals. In our study, we assessed six different types of evidence to determine whether blueberry flowers, which are typically associated with diurnal pollinators, could also be pollinated at night. We used observational and experimental approaches commonly used and validated for assessing nocturnal pollination, including variation in stigma receptivity and pollen viability at day and night, nectar standing crop dynamics, temporal effects of pollen germination, pollinator exclusion experiments and the presence of pollen on the bodies of potential nocturnal pollinators (moths). Stigma receptivity and pollen viability were similar between our day and night sample points. We found no negative effects of time of pollination on pollen germination. Nectar availability was strongly associated with time of day, and although nectar was available both day and night, nectar volume was highest at night. Fruit set was highest in flowers with unrestricted access to pollinators, but we are unable to determine the relative importance of nocturnal versus diurnal pollination as these treatments gave the same result as our control. Moths caught in blueberry orchards carried pollen from 25 plant species, with blueberry pollen being the fifth most abundant. Our results show that blueberry flowers have floral traits that allow pollination at night as well as during the day, and that moths, along with other nocturnal insects, may be contributing to this. However, the importance of nocturnal pollination relative to diurnal pollination remains unknown.