DISSERTATION RESEARCH: Flowers as hubs of nectar-microbe diversity and dispersal in flower visitor networks

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Many plants can only be fertilized when pollen is deposited on flowers by flying insects such as bees, wasps, beetles, flies, and butterflies. While these insects move around gathering nectar and pollen from flowers, they also tend to move around microbes such as yeast, bacteria, and viruses that can impact the plant or other flower visitors. For example, some of these microbes infect crops through the flowers, some infect honeybee and bumblebee colonies, and others affect whether or not an insect is attracted to the flower. While it is known that these floral microbes are moved around by insects, and affect the plant they land on, little is known about how predictable the distribution of floral microbes are in flowering plant communities. This research seeks to understand how the pattern of insect visitation to flowers affects the distribution of microbes on flowers. It is important to learn this because it could help address management of plants and insects that are critical to our food and fiber production as well as native ecosystems. Nectar-inhabiting microbes can alter floral attractiveness to pollinators and thus shape the success of pollination services. Since nectar microbes are primarily flower-visitor dispersed, they have great potential to affect and be affected by flower visitor network structure. However, the interactions of plants with their flower visitors and nectar microbes have yet to be considered in a network framework. The aim of this project is to test the hypothesis that hub plant species (plant species that have very high diversity of flower visitors) are also hubs of floral microbe diversity and dispersal in a native plant community. Network hubs are known to be responsible for a disproportionate amount of pathogen spread within animal species ("super-spreaders"). In flower visitor networks, hub plant species might function as super-spreaders of floral microbes between plant species. The project goals are to construct a dataset of plants, their flower visitors, and nectar microbe composition as well as perform a manipulative experiment on a species with high variation in flower visitors, Aquilegia formosa, in a high elevation wet meadow plant community. Simulation models will be used to evaluate the effects of visitor diversity and visitation frequency on the diversity of nectar microbes at the plant level. The researchers will empirically test the hypothesis that certain flowers are hubs of nectar microbe diversity.