Agricultural intensification favours an introduced bumble bee over its native congener through differences in foraging range, habitat association, and lineage continuity

Abstract

Agricultural intensification can enhance the expansion of introduced species which are highly adapted to human-modified landscapes, but the mechanisms by which this occurs are often unclear. Here we investigate the spatial ecology of a rapidly expanding introduced bumble bee (Bombus impatiens) and a native congener (B. mixtus) in agricultural landscapes of southwestern British Columbia, Canada. We used microsatellite genotyping and spatially explicit capture-recapture models to compare the foraging distance of the two species, and fitted hierarchical models to compare their abundance, behaviour (nest searching vs foraging), and lineage survival as a function of landscape composition and configuration. We found that B. impatiens had a broader foraging range than B. mixtus. B. impatiens colony/worker abundance were positively associated with the surrounding area of residential gardens and field edges, but decreased relative to B. mixtus abundance in response to increasing seminatural area. In contrast, B. mixtus colony abundance decreased in landscapes with a greater area of intensively managed berry crops. We observed fewer B. impatiens queens per survey in landscapes with more low-disturbance landcover, and hypothesize space use of this species could be shaped by concentration on potential nesting habitat. Consistent with this observation, nest searching behaviour was more common for B. impatiens queens, while B. mixtus queens varied in their use of certain habitat types for nest searching and were primarily observed foraging, suggesting these two species derive different value from agricultural landscapes during colony establishment. Finally, we found that the rate of lineage re-capture between 2022 colonies and 2023 spring queens was nearly 10-fold higher for B. impatiens than for B. mixtus, indicating a greater capacity of the introduced species to complete its life cycle in agro-natural landscape mosaics. Our results suggest that differences in spatial ecology may contribute to the differential success of these two species in human-modified landscapes, and provide insight into the mechanisms by which land-use change shapes community composition. Graphical abstractColoured diagrams of B. mixtus and B. impatiens are credited to Elaine Evans and the Xerces Society, with permission. O_FIG O_LINKSMALLFIG WIDTH=184 HEIGHT=200 SRC="FIGDIR/small/723627v2_ufig1.gif" ALT="Figure 1"> View larger version (60K): org.highwire.dtl.DTLVardef@136085aorg.highwire.dtl.DTLVardef@5e7b7eorg.highwire.dtl.DTLVardef@fdaa1borg.highwire.dtl.DTLVardef@1aaf4f9_HPS_FORMAT_FIGEXP M_FIG C_FIG