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

Abstract

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.

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

“…, Templ et al. ), this was not the case in the present study. In fact, the largest‐bodied taxon had the lowest number of bees netted relative to that of bees observed.…”

“…), which may alter the relative efficacy of different sampling methods (Templ et al. ). Urban areas often have a high diversity of plant associations across the region, which contrasts with often large monocultural fields in agricultural areas, and fairly uniform habitat types even in natural areas, which, however, differ from urban areas in having large, contiguous patches of native vegetation (Kaluza et al.…”

Native bee communities vary across three prairie ecoregions due to land use, climate, sampling method and bee life history traits

“…In most fields, canola grows much taller and denser than vegetation in rangelands or at field margins, and therefore pan traps placed on the ground within the canola crop would have been less visible to bees compared with the other transects. The abundance of bees captures in pan traps is affected by vegetation height and cover (Templ et al ., 2019). Similarly, pan trap height can also affect the abundance and composition of insects sampled (Tuell & Isaacs, 2008; Harris et al ., 2016).…”

Assemblages of flower-visiting insects in clear-cuts are rich and dynamic

“…Insects were caught using colour pan traps, a method designed for fl ower-visiting insects and often recommended because of its selectivity (compared with passive traps) and ability to trap over a long period of time (compared with netting). Like all methods of catching insects, it involves some bias, most notably involving fl ower abundance (Baum & Wallen, 2011;Saunders & Luck, 2013;Templ et al, 2019;Westerberg et al, 2021). The taxa studied were (i) social Apoidea, (ii) solitary Apoidea, (iii) "other Hymenoptera" (Pompilidae, Tiphiidae, Chrysidoidea), (iv) Lepturinae, (v) Cetoniinae and (vi) Syrphidae.…”