Browsing by Author "Robinson, Samuel Victor Joseph"

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    Central-place foraging, crop yield, and population change in bees: A study in canola agroecosystems
    (2019-10-01) Robinson, Samuel Victor Joseph; Cartar, Ralph Victor; Hoover, Shelley; Harder, Lawrence D.; Bender, Darren J.; Samuel, Marcus A.; Currie, Robert William
    Canola (Brassica napus L.) is a valuable crop that occupies a large part of the Canadian prairies, and is visited by wild and managed bees. However, the distribution of foraging bees in mass-flowering crops (MFCs), the value of bee visitation, and how MFCs and semi-natural land (SNL) affect wild bee populations in the context of canola agro-ecosystems is unclear. Using three separate studies, I related pollination and yield to bee visitation, and landscape composition and canola abundance to wild bee abundance. The first study examined honey bee (Apis mellifera L.) visitation in commodity canola fields using a simulation model, and revealed that honey bees most closely followed predictions for solitary efficiency-maximizers, valuing nearby flower sources much more than distant ones. The second study related visitation rates of honey bees and alfalfa leafcutting bees (Megachile rotundata (Fabr.)) to pollen deposition and seed production using a structural equation model. Leafcutter bee visitation strongly increased pollen deposiion, but not honey bee visitation, and extra pollen deposition increased seed production in seed canola, but not in commodity canola. The final study used solitary bee abundance data from a set of landscapes across southern Alberta, and related bee abundance to landscape composition from the current and previous year. While the overall response of bee abundance to SNL was positive, individual species' response to SNL ranged from positive to negative, and canola had little effect on any species' abundances. These results reveal that insect visitation in flowering crops decay rapidly with distance, that the plant growth context of canola is equally important as the pollination context, and that while the effect of SNL on wild bee abundance is generally positive, it likely varies depending on the traits of individual bee species. This work provides mechanistic insight into the foraging behaviour and contextual value of pollination by managed bees, and sheds light on how agro-ecological landscapes shape wild bee communities.