Plant-pollinator interactions of the oak-savanna: Evaluation of community structure and dietary specialization

Pollination events are highly dynamic and adaptive interactions that may vary across spatial scales. Furthermore, the composition of species within a location can highly influence the interactions between trophic levels, which may impact community resilience to disturbances. Here, I evaluated the species composition and interactions of plants and pollinators across a latitudinal gradient, from Vancouver Island, British Columbia, Canada to the Willamette and Umpqua Valleys in Oregon and Washington, United States of America. I surveyed 16 oak-savanna communities within three ecoregions (the Strait of Georgia/ Puget Lowlands, the Willamette Valley, and the Klamath Mountains), documenting interactions and abundances of the plants and pollinators. I then conducted various multivariate and network analyses on these communities to understand the effects of space and species composition on community resilience. In addition, I evaluated the pollen composition and floral visit patterns of a mid-sized mining-bee, Andrena angustitarsata, to understand how foraging preferences and dietary specialization may change across space and with varying floral compositions. I found that spatial scales had an effect on species compositions, the interactions between plants and insects, and the foraging preferences of pollinators. I learned that some groups of pollinators may provide stability in networks by increasing generalized interactions and reducing specialization. Additionally, the foraging preferences, A. angustitarsata, were conserved across spatial scales, despite fluctuations in plant compositions and abundances. However, A. angustitarsata is likely not oligolectic, a pollen specialist, because of its ability to facultatively forage on additional plants other than its preferred host plants. Overall, my results show that spatial scales can influence the composition and interactions of plants and pollinators, thus influencing the degree to which species interact and the ability of the community to maintain structure after a disturbance.