Submitted to: Journal of Kansas Entomological Society
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/3/2008
Publication Date: 7/31/2008
Citation: Wilson, J.S., Griswold, T.L., Messinger, O. 2008. Sampling Bee Communities (Hymenoptera: Apiformes) in a Desert Landscape: Are Pan Traps Sufficient?. Journal of Kansas Entomological Society 81:3 (July) Interpretive Summary: Because of concerns about the status of pollination service by bees, efficient and accurate methods of sampling them are needed. Pan trapping has become an often used method for such sampling because it requires minimal time to deploy and is thought to remove biases among collectors in net collecting, the most frequently used sampling method in the past. We used both methods on 1-hectare plots in a two-year study comparing bee communities on various parts of a complex of sand dunes in Dugway Proving Ground, in Tooele County, Utah. Pan traps of three colors detected more species except in late May and late September, times when flowering was most abundant. Similarily, they captured larger samples than nets in almost all instances. Most bees showed a preference for one color, but not typically the color of the flowers visited. The composition of species caught by the methods was complementary. It is suggested that both methods be used if a comprehensive inventory is desired.
Technical Abstract: Pan traps (colored plastic bowls) are frequently used as efficient standardized method of sampling bee faunas. We explored the utility of pan traps in three colors compared to net collecting using simultaneous sampling at biweekly intervals throughout the flowering season (May-Sep) at 11 sites in the eastern Great Basin Desert. Pan traps deployed for one day (09:00-14:00) on average captured significantly larger samples than net collections (2 hrs.) at all periods except the latter half of May. Average species richness for net collections exceeded pan traps only during late May and late September, periods with abundant floral resources. Capture rates were similar between colors. The composition of bees was also similar; Sorensen's similarity values exceed 0.7. Color preferences for pollen specialists did not match flower color of their hosts. There were significant differences in species composition between net collections and pan trap collections. Almost one-third of the species showed a strong bias toward one method and in some cases between pan trap colors. The methods appear complementary: Halictinae and Perdita were predominantly collected in pan traps (85%); three genera, Anthidium, Colletes, Epeolus were largely or entirely detected by netting. Net collecting should be used in addition to pan traps if comprehensive inventories are desired. Though pan trapping constitutes a standardized method that avoids collector bias, it may not be unbiased; capture rates were lowest when flowering plant richness was greatest.