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Roulston, Terrell Trever

University of British Columbia

Global biodiversity is under threat from a variety of factors, including habitat loss, land use change, climate change, and invasive species. Pollinators are crucial for biodiversity maintenance and global food security and are experiencing declines. One pollinator, the Western honey bee (Apis mellifera L.; Hymenoptera: Apoidea) is nearly ubiquitous in human altered landscapes. Despite honey bees being geographically widespread, knowledge of their impacts on plant-pollinator communities is incomplete. My study represents the first macroanalysis of honey bee competition in plant-pollinator networks from around the globe. Using an open-access database, I summarized bipartite network statistics for 123 plant-pollinator networks to test whether the proportion of interactions with honey bees in a network is associated with changes in network topology. Specifically, I calculated the normalized degree of interactions with honeybees (NDHB), defined as the total number of interacts divided by the richness of plant species. I predicted higher NDHB would be associated with (1) increased connectance (the realized proportion of possible interactions), (2) decreased modularity (degree of compartmentalization of subcommunities), and (3) increased nestedness (the amount of redundancy of interactions between specialist and generalist) of networks. I quantified these associations for entire networks containing all pollinators, as well as for Hymenopteran sub-networks. I also investigated whether honey bee normalized degree was associated with increased plant generalization (i.e., the mean number of links per species), and decreased pollinator generalization within Hymenopteran sub-networks. Overall, I found that honey bees were widespread, present in 77% (95/123) of networks worldwide. Results revealed that higher honey bee normalized degree was associated with decreased modularity, as well as increased plant generalization and increased pollinator generalization. Contrary to expectations, honey bee introduction was not associated with changes to network connectance or nestedness. While the results are correlational, they suggest that this widely introduced species is capable of modifying the structure of plant-pollinator networks leading to the homogenization of interactions, which could impact the persistence and coexistence of native plants and pollinators.

Text

2024-01-04

Attribution-NonCommercial-NoDerivatives 4.0 International

http://hdl.handle.net/2429/87073

Plant Science

University of British Columbia

UBCV

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