University Honors

Urbanization leads to the cultivation of non-native horticultural and weedy plant species, which provide abundant floral resources and may dominate pollinator diets. Flowers are major conduits of microbial transmission, shaping the potential transfer of microbes between pollinators. Studying how the abundance of microbes within floral microbiomes changes over a season may help us understand some of the impacts of global climate change on pollinators and plants. To investigate these trends, I monitored urban gardens on and around the University of California, Riverside campus, recording ambient temperatures, humidity, wind speed, and I conducted pollinator surveys at a specified time once per week. At the same time, I aseptically collected whole flower head samples for culturing on Pollen Extract (PE) medium, a modified de Man, Rogosa, and Sharpe with Pollen Extract (MRS-PE) medium, and a modified Tryptic Soy Agar with Pollen Extract (TSA-PE). I tested how bacterial Colony Forming Units (CFU) correlated with environmental factors. As temperatures lowered, CFU counts increased, while rising temperatures correlated with decreased CFU counts. Urban environments are known as heat islands due to large areas of impervious, heat retaining surfaces. Higher temperatures led to fewer culturable floral microbes, suggesting that climate change may negatively affect floral microbiomes, thereby posing an increased epidemiological risk to plants and pollinators.