Sampling technique affects detection of habitat factors influencing wild bee communities

Authors: RHOADES, PAUL - University Of Idaho; Griswold, Terry; WAITS, LISETTE - University Of Idaho; BOSQUE-PEREZ, NILSA - University Of Idaho; KENNEDY, CHRISTINA - Nature Conservancy; EIGENBRODE, SANFORD - University Of Idaho

Submitted to: Journal of Insect Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 7/21/2017
Publication Date: 7/20/2017
Citation: Rhoades, P., Griswold, T.L., Waits, L., Bosque-Perez, N.A., Kennedy, C.M., Eigenbrode, S.D. 2017. Sampling technique affects detection of habitat factors influencing wild bee communities. Journal of Insect Conservation. 21(4):703-714. https://doi.org/10.1007/s10841-017-0013-0.
DOI: https://doi.org/10.1007/s10841-017-0013-0

Interpretive Summary: There is concern that pollinators, particularly bees, may be in decline. This would have consequences for pollination and general ecosystem health. The extent to which declines are occuring is unknown, both in terms of what areas could be impacted and which pollinating species are affected. Accurate monitoring methods to detect changes in bee populations are necessary to guide conservation efforts. Three commonly used methods for sampling bees (blue vane traps, colored pan traps, and insect net collections) were compared at fragments of native habitat in the Palouse Prairie of eastern Washington and northern Idaho. There are differences between the three sampling methods in abundance, number of species detected, and the relative proportions across bee genera. The effect of plant diversity on these methods was analyzed since having a diversity of flowers is known to affect bee diversity. The effect of the amount of good bee habitat in the areas surrounding the fragments was also tested. Collecting with nets was most affected by the diversity of plants. Blue vane traps were most influenced by the amount of good bee habitat surrounding the patches of native habitat. Pan traps were not as affected by either plant diversity or presence of surrounding native habitat. This study can help to inform choices of the most effective ways to monitor bee populations depending on context.

Technical Abstract: 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 the 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, the proportion of captured insects representing different genera, and functional trait characteristics among the three sampling techniques. We also evaluated differences in the relationships between bee community metrics 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 underscore that effective conservation of insect communities will require sampling methods that can reliably discern the influence of habitat variables at different scales and across taxa with varying functional traits.