Flower visitation and land cover associations of above ground- and below ground-nesting native bees in an agricultural region of south-east Australia

Abstract

How different forms of agriculture support different bee taxa through the provision of different floral and nesting resources is largely unknown. Recent studies have found wild bees that are associated with agriculture tend to nest in soil, rather than vegetation, and so are thought to be adapted to open environments where perennial woody vegetation is sparse. However, these studies do not usually distinguish different forms of agriculture, such as open pasture versus perennial woody crops. It is possible that bees that nest in wood or stems might be tolerant of agriculture with perennial woody crops, but this idea has not been tested in landscape studies. We describe foraging preferences and land cover associations of wild bees in southeast Australia to ask: Do perennial woody crops support bees that nest in wood or stems (above ground-nesting bees), while pasture supports soil-nesting (below ground-nesting) bees? We sampled bee communities using blue vane traps and flower visitor observations at 14 sites that varied in cover of remnant forest, perennial woody crops, and pasture. We found that soil-nesting bees were positively associated with pasture cover in the landscape, except for bee taxa that rarely visited crops or agricultural weeds. Above ground-nesting bees were positively associated with forest, but not with perennial woody crop cover, despite frequently visiting flowers on these crops. Our results suggest conversion of native forest to open agriculture favours soil-nesting bee taxa that forage on crops and weeds, while restricting bee taxa that depend on forests for nesting or floral resources.