Factors influencing coastal bee communities at Marin Headlands and Point Reyes National Seashore

Abstract

Coastal habitats are vulnerable to recreational use. Stressors such as habitat degradation through human activity are particularly detrimental. Although conservation efforts have been taken to preserve these unique habitats, coastal habitats are poorly understood. This project aims to understand what species of bee pollinators use these coastal habitats, what host plants they pollinate, and how they are affected by human activity. I surveyed 8 established sites using hand netting and documented the flowering plants in bloom on each visit. I used distance to a parking lot as a proxy for recreational use and determined whether sites are adjacent to grazing land. I found that with high recreational use, bee species richness and abundance and plant abundance increased on ungrazed sites but decreased on grazed sites. Of the plant-pollinator network parameters measured, only the interaction between ungrazed sites and recreational use for generality, the mean number of plant species with which bees interact, was significant. These results suggest that the effects of recreational use differ between grazed and ungrazed sites. In ungrazed areas, the impacts of recreational use on plant and pollinator communities may be important for land managers to monitor. v Acknowledgements I would like to give a big and warm thank you to my family for sticking with me the whole way on this journey on completing my thesis. I would also like to give a big thank you to Gretchen Lebuhn, this could not have been possible without her help and deep insights. A thank you to my committee members Andrea Swei and Nicole Adelstein for helping me make this paper the best that it could possibly be. Another big thank you to SEPAL, specifically Kimberly Tanner, Trisha DeVera and Lucy Luong. A thank you to OneTam for funding this project, and a thank you to Sara Leon Guerrero and Lisette Arellano. And lastly a big thank you to the Nelson Scholarship Award for Conservation Biology (2020) and the Bioluminary award (2019) for helping me cover tuition costs. vi