Sampling technique affects detection of habitat factors influencing wild bee communities

Reliable and consistent monitoring is essential for bee conservation. Correctly interpreting the influence of habitat characteristics on native bee communities is necessary to develop effective strategies for bee conservation and to support the provision of pollination services to agricultural crops or natural plant communities. Biases imposed by different sampling methods used to monitor bee populations can affect our ability to discern important habitat characteristics, but the extent of this bias is not well understood. We used three common sampling methods (blue vane traps, colored pan traps, and aerial net collection) to assess bee communities in fragments of Palouse Prairie in eastern Washington and northern Idaho. We determined differences in abundance, species richness, proportional representation of different genera, and functional trait characteristics among the three sampling techniques. We also evaluated differences in the relationships between bee species richness and diversity and two key habitat variables known to mediate bee populations: local plant species richness and the amount of suitable bee habitat in the surrounding landscape. Community metrics for bees collected using blue vane traps were correlated with the amount of suitable habitat in the landscape but not with plant species richness. Conversely, community metrics for bees collected using an aerial net were correlated with the local plant species richness but not with the amount of suitable habitat. Our results indicate that effective conservation of insect communities will require a combination of sampling methods to reliably discern the influence of habitat variables at different scales and across taxa with varying functional traits.