Plant-pollinator communities and interactions across diverse agricultural landscapes

Rachel Lynn Olsson

Insects pollinate around 70% of crops globally. Facing climate change and declining bee populations, it is critical to conserve pollinators to maintain an adequate food supply for a growing human population. Pollinator declines have been linked to decreasing habitat and food resources caused by anthropogenic influence like development and agriculture. This dissertation addresses these issues from several angles. The first chapter is an observational study of pollinator communities across urban and rural farms in western Washington State. This study found that flies made up 34% of floral visits and visited flower types not visited by bees. Identifying alternative pollinators may lead to improved conservation efforts. The second chapter is a review of the agricultural history of the inland northwest region of the United States and how that history may affect bee communities. Recently, many growers have added canola to their crop rotation, the inland northwest has experienced a flush of floral resources that could support bees. This chapter addresses the ways growers can support pollinators and gain financial benefit from the improved pollination of their crop. Because canola is a newly introduced crop in this region, the pollinator community has gone largely unstudied. The third chapter is a two-year observational study on the pollinator populations in canola, and an examination of landscape and environmental affects that may alter the community makeup. Increased development had a negative effect on pollinator abundance and biodiversity, while floral attributes had a positive effect on pollinator communities. These floral traits were the focus of the final chapter. Canola plants of three varieties were grown in greenhouse conditions and exposed to drought and a soil-borne fungal pathogen damaging to wheat. Plants exposed to drought produced fewer flowers, lower volume of nectar, and had smaller petals compared to control plants. Plants exposed to a fungal pathogen exhibited the opposite response. This study indicates that canola may be an acceptable alternative to wheat when pathogen is present in the soil, and that the flowers may be more attractive to pollinators through the landscape. These chapters will inform future pollination biologists and growers in this region on conservation methods.

Plant-pollinator communities and interactions across diverse agricultural landscapes

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