The effect of fire disturbance on bee community composition in oak savannah habitat in Southern Ontario, Canada
Pindar, Alana N.
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Determining how bee communities respond to environmental disturbance is crucial for ensuring that the pollination service that bees provide is sustained. Studies have reported that bee communities respond to environmental disturbance; however they have not experimentally tested whether environmental disturbances are important for maintaining bee diversity. Unlike other studies of the impact of fire upon bees, this thesis is based upon experimental tests. I investigate whether fire disturbance plays a significant role in maintaining bee community diversity and composition, and how individual species occupy various ages of post-burn habitat. Freshly burned (< 4 years since fire), intermediate burn (5-10 years since fire), mature burn (15-20 years since fire) and control (no fire) plots were used in two oak savannah remnants in Southern Ontario. Results show fire to be an important environmental disturbance for maintaining bee diversity in the temporal sense, as bee diversity was at its highest in intermediate age burns. Bee diversity increased significantly immediately post fire in fresh habitat but high diversity was short lived whereas mature site bee diversity declined over time. Rank abundance plots and community composition analyses revealed bee communities differed in species composition among replicates of the same age since fire within localities and over time. Bee communities within localities showed similarities in composition. Functional nesting guilds examined were solitary and social ground nesters, cavity nesters, Bombus spp. and cleptoparasites. The relative proportional abundance of species within functional nesting guilds also varied over time and burn site. An examination into how bee species within functional guilds occupy burned habitat indicated that bee species of the same functional guild occupy burned habitat differently. Occupancy modeling of the 12 most common bee species suggests the need for more thorough assessments of the ecologies of individual species in order to fully determine how bee communities respond to environmental disturbances.