Pollination ecology of lowbush blueberry (Vaccinium angustifolium Aiton) in an island ecosystem

Abstract

Plant pollination is influenced by plant traits, pollinator community, plant community, and abiotic conditions. Island ecosystems, which often have reduced pollinator communities, provide unique insights into pollination ecology. Lowbush blueberry, Vaccinium angustifolium Aiton, has predominantly been studied in managed agricultural areas with introduced honeybees. We examined diurnal and nocturnal pollination of unmanaged lowbush blueberry patches on an 80 ha island in New Brunswick without honeybees. We restricted pollinator access to blueberry stems in five different treatments. Using mesh bags, we made stems accessible to pollinators 24 h a day (positive control), only during the day, only at night, or never (negative control), with an additional sham control. Blueberry stems accessible only to diurnal visitors had 70.55% fruit set and a mean 7.33 viable seeds per fruit. Stems accessible only to nocturnal visitors had 63.76% fruit set and 5.87 viable seeds, significantly higher than the continuously bagged negative control stems. The most common diurnal insects observed visiting flowers were bumblebees and two wasp species. Insects collected from plants at night were beetles and flies. There was substantial variation between blueberry patches in fruit set and fruit size. We examined whether flower color could be driving patch differences in pollination, and quantified flower color using spectrophotometry. We found no effect of flower color on metrics of pollination. As well as demonstrating substantial nocturnal pollination, we record unusually high fruit set, especially for an island without managed bees. We discuss some of the potential drivers of this high fruit set.