COS 166-1 - Tropical urban bees and their response to Hurricane Fiona

Abstract: Background

Natural disasters and urbanization are two distinct types of disturbance that have profound impacts on biodiversity. The frequency and intensity of extreme weather events, such as hurricanes, are projected to increase due to climate change. The world is also quickly becoming more urban, which increases the likelihood of extreme weather events occurring in cities and other urban areas. Since some cities can support higher levels of biodiversity than expected, it is important to understand how urban biodiversity responds to such events. In September 2022, Hurricane Fiona struck Puerto Rico while we were in the middle of a study surveying bee community assembly in the San Juan metropolitan area. This provided us with the unique opportunity to assess the response of bee communities to a large-scale natural disturbance in an urban environment. We compared bee community composition and structure pre- and post-hurricane in both urban and peri-urban areas.



Results

We found a significant difference (p< 0.0001) in the species richness of the urban bee communities in the four months prior (S = 5 ± 2.16) versus the four months after (S = 3.25 ± 2.5) the hurricane. When comparing the three months pre- and three months post-Hurricane Fiona, the significance was still detected (p=0.0002). We also observed significant differences (p=0.0039) in bee species richness at the per-urban sites two months before (S = 4.5 ± 0.71) and two months after (S = 2.5 ± 2.12) the hurricane. Bee abundances also decreased by half in both the urban (n=172 vs 70) and the peri-urban (n=30 vs 15) sites. All species experienced population declines after the hurricane, but Lasioglossum enatum, the dominant species in both the urban and peri-urban sites, experienced the greatest decrease. As of January 2023, L. enatum has not been observed at any peri-urban site. As we continue to observe bee communities in San Juan, we will be able to compare their post-hurricane compositions and abundances to those at the same time last year. We will also assess bee floral resource utilization to see how floral diversity influences bee diversity and abundance after the hurricane.