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O'Neill, Erin

Biology

2020

M.S.

Most angiosperms rely on animal pollination to reproduce and the majority of these also interact with mycorrhizal fungi. Although these interactions have been studied separately, few studies have examined their combined effects on host plants. Linking above and belowground interactions has become an exciting new field of study. Ericoid mycorrhizae (ericoids) are the relationship between certain taxa of fungi and plants in the Ericaceae, including Vaccinium corymbosum, the highbush blueberry. Here, I asked whether inoculation with ericoid mycorrhizal fungi altered resource allocation to floral buds and flowers of V. corymbosum. Different fungi may vary in their ability to assist their plant partners with nutrient uptake and to address this, I inoculated plants with either a commercial or local fungal inoculum. Inoculation with ericoids may change the number of V. corymbosum buds and flowers and/or affect floral traits, by enhancing nutrient uptake. If the floral traits that are affected are important to pollinators, mycorrhizae could indirectly affect the host plant's interaction with pollinators. I hypothesized that inoculation with ericoid mycorrhizal fungi increases seed set in V. corymbosum, through its effects on floral traits and pollinator visitation, and responds more strongly to a local soil inoculum than to a commercial inoculum. To test my hypothesis, I inoculated 380, two-year old V. corymbosum plants in the spring of 2018 and randomly assigned them to one of five treatments: 1) commercial inoculum, in a peat base 2) local soil, 3) commercial inoculum and local soil, 4) a control group with no inoculum, and 5) peat base used for the commercial inoculum. Plants were then grown in a common garden. In the summer of 2019, I transported plants to blueberry farms known to differ in pollinator abundance and conducted pollinator observations throughout the flowering season. In addition, I conducted hand-pollination experiments to examine the degree of pollen limitation at each of these farms. My results show that inoculation with ericoids directly enhanced the chances of plants flowering but did not alter interactions with pollinators. My results elucidate the importance of ericoids for the development of reproductive traits.