Pan traps and bee body size in unmanaged urban habitats

Mózes

Journal of Apicultural Science

et al. 2019

Bees are the most important group of flower visitors providing an essential ecosystem service, namely pollination. Due to the worldwide decline of bees, there should be standardized sampling methods in place to ensure consistent and comparable results between studies. We compared the two commonly used sampling methods of yellow pan traps and transect walk to determine (i) which habitat variables affect the species composition, abundance and species richness of sampled bee communities, (ii) which method potentially contains sampling bias towards some individuals or groups of bees and (iii) the efficiency of sampling in various habitats. We conducted fieldwork in different agricultural habitats distributed along landscape heterogeneity and topography gradients. Our results showed that the height of vegetation, the average number of flowers and the amount of woody vegetation had the greatest influence on the sampling efficiency. Our survey also demonstrated that sampling by transect walk captured less bees in general, especially in stubble, maize, and cereal fields. We found that Apis mellifera and Bombus spp. were well represented in samples collected by the transect walk method, while the abundance of other genera, especially Dasypoda, Hylaeus and Panurgus was higher in pan traps. Based on the results, we suggest (i) the transect walk method to compare samples of flower-visiting wild bee communities from various habitats of different vegetation and flower characteristics, (ii) application of the transect walk or pan traps to compare similar habitats and (iii) adoption of a comprehensive method which would incorporate both sampling techniques to gain a more complex insight into wild bee species composition.

Section: Discussionmentioning

confidence: 77%

Habitat-Dependency of Transect Walk and Pan Trap Methods for Bee Sampling in Farmlands

Mózes

Journal of Apicultural Science

et al. 2019

“…Our results suggest context-dependent effects of the DCF, as umbel height influenced the attractiveness of the DCF in the studied population of D. carota. At least one study, using pan-traps, demonstrated that height, even as small as 70 cm above ground, may play a significant role in the kinds of bees collected, especially in their average body size (Gonzalez et al 2016). In natural systems, distinctions have even been made between large-and small-bodied bees and the plant -D, respectively).…”

Section: Resultsmentioning

confidence: 99%

Attractiveness of the dark central floret in wild carrots: do umbel size and height matter?

et al. 2018

The function of the dark central floret (DCF) in the wild carrot, Daucus carota L. (Apiaceae), is uncertain. It has been suggested that it is a vestigial structure without a function, that it serves as a long or short distance signal to attract pollinators, or that it might function as a defense mechanism against herbivores. We experimentally assessed the role of the umbel size and height in the attractiveness of the DCF to insects in a coastal population of D. carota in western Turkey. We did not find differences in the number of insect visits between umbels with a DCF and umbels in which the DCF was removed when they were of average diameter (10 cm) and were placed either at the average inflorescence height (120 cm) or at 147 cm above ground. Similarly, we did not find differences in the number of insect visits before and after the removal of the DCF from an umbel or between umbels of small (5–7 cm) and large (11–13 cm) diameters. However, umbels of average diameter with DCF received more insect visits than those without it when we placed them at 81 cm above ground. These results suggest that umbel height, not diameter per se, influences the attractiveness of the DCF in the studied population. Thus, our study supports the hypothesis that DCF function depends on ecological context, reliant on both the visitor community and the predominant flower phenotype.

“…However, the sampling method used may be biased toward bees of a particular lineage or functional group, meaning that the appropriate sampling method varies depending on the taxonomic group or question at hand (Gonzalez et al. , Sircom et al. , McCravy et al.…”

Section: Introductionmentioning

confidence: 99%

The relative performance of sampling methods for native bees: an empirical test and review of the literature

et al. 2020

Many bee species are declining globally, but to detect trends and monitor bee assemblages, robust sampling methods are required. Numerous sampling methods are used, but a critical review of their relative effectiveness is lacking. Moreover, evidence suggests the relative effectiveness of sampling methods depends on habitat, yet efficacy in urban areas has yet to be evaluated. This study compared the bee community documented using observational records, targeted netting, mobile gardens, pan traps (blue and yellow), vane traps (blue and yellow), and trap‐nests. The comparative surveys of native bees and honeybees were undertaken in an urbanized region of the southwest Australian biodiversity hot spot. The outcomes of the study were then compared to a synthesis based on a comprehensive literature review of studies where two or more bee sampling methods were conducted. Observational records far exceeded all other methods in terms of abundance of bees recorded, but were unable to distinguish finer taxonomic levels. Of methods that captured individuals, thereby permitting taxonomic identification, targeted sweep netting vastly outperformed the passive sampling methods, yielding a total of 1324 individuals, representing 131 taxonomic units—even when deployed over a shorter duration. The relative effectiveness of each method differed according to taxon. From the analysis of the literature, there was high variability in relative effectiveness of methods, but targeted sweep netting and blue vane traps tended to be most effective, in accordance with results from this study. However, results from the present study differed from most previous studies in the extremely low catch rates in pan traps. Species using trap‐nests represented only a subset of all potential cavity‐nesters, and their relative abundances in the trap‐nests differed from those in the field. Mobile gardens were relatively ineffective at attracting bees. For urbanized habitat within this biodiversity hot spot, targeted sweep netting is indispensable for obtaining a comprehensive indication of native bee assemblages; passive sampling methods alone recorded only a small fraction of the native bee community. Overall, a combination of methods should be used for sampling bee communities, as each has their own biases, and certain taxa were well represented in some methods, but poorly represented in others.