D3136: Coupled impacts of variable precipitation patterns and habitat fragmentation on native bee assemblages in a biodiversity hotspot

Monday, November 11, 2024

9:00 AM – 5:00 PM MST

Location: Phoenix Convention Center, Exhibit Hall 6, PCC

Presenting Author(s)

Jessica L. Mullins

PhD Student
University of California
La Jolla, California

Co-Author(s)

Keng-Lou James Hung (he/him/his)

Assistant Professor of Biology
University of Oklahoma
Norman, Oklahoma
JA

John S. Ascher (he/him/his)

National Univerisity of Singapore
Singapore, Singapore
DH

David A. Holway

University of California
La Jolla, California

Insect populations, including wild bees, are declining and the extent and underlying reasons are debated. Globally, land-use change through habitat loss and fragmentation and climate change are implicated in these patterns of decline. The landscape of western San Diego County, California has many preserved small habitat patches isolated by urban matrix and offers an ideal study system to assess how habitat fragmentation and climate change drive biodiversity loss. Here, we present findings related to how these synergystic stressors interact to influence native bees on an community level. Our dataset, which spans a 12-year period (2011-2023) encompasses six survey seasons from plots with similar plant communities that are classified as reserves or fragments (internal area = >500 ha or < 120 ha). Our results show that fragments support 28% fewer species versus reserves across all survey years. We compared the previous year’s accumulative annual precipitation, and found that above- or below- average precipitation preceding a survey year does not change the bee richness in fragments, however, increased precipitation leads to a 17% increase in species richness in reserves (p < 0.01). These findings confirm that reserves host a greater diversity of bee species that respond positively to large rainfall events. This research highlights the importance of preserving large, connected ecosystems and further assesses how land-use and climate change interact to alter biodiversity and underscores the importance of determining which landscape factors are responsible for local extinction events and which species are most vulnerable to anthropogenic stressors.