Does urbanization favor exotic bee species? Implications for the conservation of native bees in cities

A growing body of research indicates that cities can support diverse bee
communities. However, urbanization may disproportionately benefit exotic
bees, potentially to the detriment of native species. We examined the
influence of urbanization on exotic and native bees using two datasets
from Michigan, USA. We found that urbanization positively influenced
exotic – but not native – bee abundance and richness, and that this
association could not be explained by proximity to international ports of
entry, prevalence of exotic flora, or urban warming. We found a negative
relationship between native and exotic bee abundance at sites with high
total bee abundance, suggesting that exotic bees may negatively affect
native bee populations. These effects were not driven by the numerically
dominant exotic honeybee, but rather by other exotic bees. Our findings
complicate the emerging paradigm of cities as key sites for pollinator
conservation.