Open Collections

Knoerr, Sarah Alexandra

University of British Columbia

To preserve the pollination services provided by declining wild bees, we must prioritize management practices that incorporate resources for pollinators within intensely farmed areas. In particular, nesting habitat represents a critical knowledge gap in bee ecology, limiting our ability to develop and implement effective conservation strategies. Grassland set-asides (GLSAs), agricultural fields periodically removed from production and planted with grasses and forbs, have the potential to provide nesting sites for wild ground-nesting bees, such as bumble bees (genus Bombus), due to their low disturbance and minimal pesticide exposure. To assess the capacity of GLSAs to provide quality nesting sites for bumble bees, I conducted surveys across various habitat types in agricultural areas where GLSAs are a common management practice. In the spring of 2023, I recorded observations of nest-searching queens to determine their habitat preferences, mapped out workers captured throughout the landscape and collected worker tarsal samples to estimate colony density via microsatellite analysis. Nest-searching queens exhibited a strong preference for GLSAs, comparable to other similarly undisturbed habitats such as unused grassy areas, and significantly surpassing crop fields, pastures and roadsides. The presence of GLSAs in intensely farmed areas was also a strong predictor of native bumble bee worker density, and, in particular, supports higher native Bombus mixtus nest densities, suggesting that these habitat amendments support bumble bee populations in agroecosystems beyond the colony establishment stage. I also found evidence for species-level differences in nesting habitat preferences, but further investigation is needed to identify the mechanisms that underlie these differences. Overall, GLSAs were identified as quality nesting habitat for bumble bees, provided their return to production doesn’t interrupt the colony cycle.

Text

2024-12-24

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/89997

Plant Science

University of British Columbia

UBCV

http://creativecommons.org/licenses/by-nc-nd/4.0/