| Abstrakt: |
AbstractFor solitary bees, nesting substrate availability may limit population growth. Here, we investigate the nesting of a locally abundant bee Osmia conjunctaCresson (Hymenoptera: Megachilidae) in empty shells of exotic snails, Cepaeaspp. Held (Stylommatophora: Helicidae), in Hamilton, Ontario, Canada. A literature review determined that O. conjunctawas sparsely distributed throughout its range, with a low relative abundance except for the Niagara Region of Ontario, Canada, three sites in Maryland, United States of America, and the focal study area in Hamilton, Ontario. The Hamilton field survey of five grassland bee communities found O. conjunctato be the most abundant bee species. The average relative abundance was 18.7%, peaking at 87% on one spring day. A survey of 1088 empty snail shells was done at the site with the highest O. conjunctaabundance. It revealed an average of 10.87 empty shells per square metre with cocoons in 9.8% of the shells, averaging 1.6 cocoons per nest. The relation between shell traits and cocoon presence indicated that O. conjunctapreferred nesting in shells with intermediate size and colour and avoided shells near shrubs. The presence of Cepaeasnails increased O. conjunctapopulations with potential consequences to the local bee assemblage. |
