Browsing by Author "Retzlaff, Jennifer Leigh"

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    How Landscape Filters Local Abundance: A Test of the Body Size-Foraging Range Hypothesis in Bumble Bees
    (2018-03-09) Retzlaff, Jennifer Leigh; Galpern, Paul; Cartar, Ralph Victor; Bender, Darren J.; Flanagan, Kyla M.; Pavelka, Mary McDonald
    For central place foragers, foraging range increases with body size. This is true for eusocial pollinators such as bumble bees, for whom body size dictates the maximum distance to which foragers can travel from their nest. Body size should therefore influence the size of landscape over which floral resources are accessible, and indirectly affect local abundance. Given this dispersal constraint, landscape should be an environmental filter for bees based on their body size, resulting in a size-based distribution of abundances in the local bee community reflecting the distance-based availability of resources. In this way, the abundance of bumble bees should reflect landscape composition. I found that the abundance of queens in Southern Alberta was related to an interaction between the amount of semi-natural land cover (a measure of foraging resources for bees) at two spatial scales: near the nest (local; 0 – 500 m) and further afield (broad; 500 – 2000 m). Small queens were more abundant when local availability of semi-natural land was moderate or high, and broad availability of semi-natural land was at low or moderate. The converse was not true: large queens were not more abundant when local resources were poor, and broad resources high. Worker abundance increased with local semi-natural land cover, but surprisingly showed no sign of this relationship being mediated by body size, suggesting that landscape composition influences the body size composition of bumble bee communities primarily during the nest establishment phase by queens. I conclude that the body size-foraging range hypothesis is generally unsupported in my system, but the hypothesis received partial support in the case of small-bodied queen bumble bees being more abundant when amount of local semi-natural habitat was high.