Inventorying and monitoring crop pollinating bees: Evaluating the effectiveness of common sampling methods

Abstract

1. Wild bees provide a critical ecosystem service by pollinating globally important crops. Documented bee declines, notably in agricultural landscapes, therefore threaten future food security. Yet, evaluations of methods to inventory bees are rarely carried out in different crops or focus specifically upon crop pollinating species.2. We utilise standardised field datasets to elucidate differences in the capacity of transect walks, observation plots and pan traps to sample wild bee pollinator communities in four contrasting crops. Our results indicate that individual survey methods detect different components of crop pollinator communities, with guild and body size potentially important causal factors behind these differences.3. Transects detected half or less of the total potential pollinator community in three of our four study crops. Whilst transects were the most efficient method for sampling bumblebees, they often missed smaller solitary species, which were most efficiently sampled by yellow pan traps.4. Crop type is likely an important determinant of the most suitable survey methods to sample bee pollinator communities. Whilst transects alone are sufficient in crops pollinated predominantly by bumblebees, pan traps, and potentially observation plots, may be an important addition in some crops where smaller solitary bee species are potentially important pollinators. 5. Our results indicate that the most efficient methods to sample bee species in agricultural landscapes are dependent upon crop type and pollinator community composition. We use our findings to make a set of recommendations on the inventorying and monitoring of bee pollinator crop communities that can inform regional and national monitoring programmes.

Different Distribution Patterns of Hoverflies (Diptera: Syrphidae) and Bees (Hymenoptera: Anthophila) Along Altitudinal Gradients in Dolomiti Bellunesi National Park (Italy)

“…Several investigations compared the efficiency of different methods in sampling hoverflies and especially bees [ 53 , 56 , 57 , 58 ]. Pan traps and entomological nets along transects proved to be the most efficient methods, though not fully exhaustive.…”

“…Both hoverflies and bees were sampled by coloured pantraps: white, blue, and yellow, as suggested in current literature [ 53 , 54 , 55 ]. Pan traps and active netting along transects are considered the most suitable methods to sample bees for their efficiency, repeatability, and standardization [ 53 , 56 , 57 , 58 ]. We decided to use pan traps instead of entomological nets in order to avoid a potential sampling bias due to the collector; furthermore, given the high climate variability over time along the gradient, we preferred a sampling method that would reduce the field time.…”

Evaluating the effects of observation period, floral density, and weather conditions on the consistency and accuracy of timed pollinator counts

“…These pollinator declines are of major concern because they represent a fundamental loss of biodiversity and because of the immediate implications for food production. Consequently, much research has been generated to demonstrate and clarify relationships between pollinator communities and the 'health' of agro-ecosystems, along with repeated calls to initiate long-term monitoring programs of pollinator abundance and diversity (Lebuhn et al 2013;Dicks et al 2021;Hodge 2020;Hutchinson et al 2022;Krahner et al 2021).…”

“…Several passive and active sampling methods are used to study insect pollinators, and several previous papers have compared and contrasted the value and weaknesses of these different techniques (e.g. Westphal et al 2008;O'Connor et al 2019;Prendergast et al 2020;Hutchinson et al 2022;Krahner et al 2021;Thompson et al 2021;Leclercq et al 2022). The sampling method adopted in any given study often reflects the prior experiences of the researchers, as well as the scale of the project and the research aims, so the data set obtained is fit for purpose (Westphal et al 2008).…”

“…The sampling method adopted in any given study often reflects the prior experiences of the researchers, as well as the scale of the project and the research aims, so the data set obtained is fit for purpose (Westphal et al 2008). Additionally, consideration is often given to which and how many pollinator groups are being investigated, the level of taxonomic resolution required, and the time, labour, and resources available to carry out the research (Westphal et al 2008;Hutchinson et al 2022).…”