Changes in the bee fauna (Hymenoptera: Apoidea) of an old field site in southern Ontario, revisited after 34 years

Abstract

We investigated changes in a wild bee community by repeating a detailed historical study of bee biodiversity in Ontario. In 1968 and 1969 (period 1), an inventory of bee species was taken from an old field habitat in southern Ontario. We resampled the bee fauna in 2002 and 2003 (period 2), following the same methods. Bee species richness, diversity, and evenness were significantly greater in period 2, and this was observed in all functional guilds except wood-nesting, pollen specialist, and nonnative bees. In period 2, a total of 150 bee species were found (2002, 98 species; 2003, 143 species), whereas in period 1, a total of 105 species were found (1968, 98 species; 1969, 76 species). Although 90 bee species collected in period 1 were re-collected in period 2, bee community composition was remarkably different between periods, with an estimated community similarity of only 7.5%. Changes in the bee fauna, specifically the increase in the proportions of pollen specialist and wood-nesting bees, might be best explained by changes in the habitat as a result of succession over the intervening 34 years. We compare and contrast our findings of bee community change with the published literature and discuss the possible factors driving the change.

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