Plant-Pollinator Interactions in Lowbush Blueberry Agroecosystems

Abstract

Lowbush blueberry (Vaccinium angustifolium Aiton, Ericales: Ericaceae) is a shrub native to northeastern North America. Wild bees have co-evolved with lowbush blueberry and are effective pollinators. The objective of this thesis was to describe plant-pollinator interactions in lowbush blueberry ecosystems in Maritime Canada. The specific objectives were 1) to evaluate correlations between plant richness, abundance, and diversity and bee visits to lowbush blueberry 2) determine which wild bees collected pollen from lowbush blueberry and 3) which non-crop flowers wild bees collected pollen from over the season. Interactions were characterized at 28 site-years. Observations of bee visits to flowers were recorded during transect walks and a subset of wild bees were captured for DNA metabarcoding of bee-associated pollen. Significant correlations between plant metrics and bee visits to blueberry were rare. During bloom, andrenid bee visits to blueberry were positively correlated to plant richness and diversity in the field. Bumble bee visits to lowbush blueberry were positively correlated to the mean bloom abundance (excluding blueberry) in the field. Other wild bee visits to blueberry were positively correlated to bloom abundance in the fall. Bees were observed on 55 of the 113 plant taxa recorded. The most abundant wild bees observed on blueberry flowers were the long-lived, social Bombus spp. and Lassioglossum spp. as well as the short-lived, solitary Andrena spp. At some sites, wild bees were observed on blueberry more frequently than honey bees. All wild bee taxa captured carried Vaccinium spp. pollen. In fact, 96% of captured bees carried Vaccinium spp. pollen, and 52% of captured bees had only Vaccinium spp. in their pollen loads. During bloom 86% of wild bee pollen loads had three or fewer plant genera. There were very few significant differences among bee taxa for the number of plant genera present in pollen loads. DNA metabarcoding of bee-associated pollen revealed more plant- pollinator interactions than observations during transect walks. The most common non- blueberry plant families in pollen loads during bloom were Rosaceae, Sapindaceae, and Asteraceae. Asteraceae was the most common plant family in summer and fall pollen loads. This study identified the wild bees present in lowbush blueberry fields. Observations and bee-associated pollen revealed the plant taxa wild bees visited throughout their lifecycle. These data identified plants that support wild bees in lowbush blueberry agroecosystems.