Measuring Bee Diversity in Different European Habitats and Biogeographical Regions

Abstract

Bee pollinators are currently recorded with many different sampling methods. However, the relative performances of these methods have not been systematically evaluated and compared. In response to the strong need to record ongoing shifts in pollinator diversity and abundance, global and regional pollinator initiatives must adopt standardized sampling protocols when developing large‐scale and long‐term monitoring schemes. We systematically evaluated the performance of six sampling methods (observation plots, pan traps, standardized and variable transect walks, trap nests with reed internodes or paper tubes) that are commonly used across a wide range of geographical regions in Europe and in two habitat types (agricultural and seminatural). We focused on bees since they represent the most important pollinator group worldwide. Several characteristics of the methods were considered in order to evaluate their performance in assessing bee diversity: sample coverage, observed species richness, species richness estimators, collector biases (identified by subunit‐based rarefaction curves), species composition of the samples, and the indication of overall bee species richness (estimated from combined total samples). The most efficient method in all geographical regions, in both the agricultural and seminatural habitats, was the pan trap method. It had the highest sample coverage, collected the highest number of species, showed negligible collector bias, detected similar species as the transect methods, and was the best indicator of overall bee species richness. The transect methods were also relatively efficient, but they had a significant collector bias. The observation plots showed poor performance. As trap nests are restricted to cavity‐nesting bee species, they had a naturally low sample coverage. However, both trap nest types detected additional species that were not recorded by any of the other methods. For large‐scale and long‐term monitoring schemes with surveyors with different experience levels, we recommend pan traps as the most efficient, unbiased, and cost‐effective method for sampling bee diversity. Trap nests with reed internodes could be used as a complementary sampling method to maximize the numbers of collected species. Transect walks are the principal method for detailed studies focusing on plant–pollinator associations. Moreover, they can be used in monitoring schemes after training the surveyors to standardize their collection skills.

Does Landscape Complexity and Semi-Natural Habitat Structure Affect Diversity of Flower-Visiting Insects in Cucumber Fields?

“…Research by Menalled, Marino, Gage, & Landis (1999) found that complex landscape had higher diversity of parasitoids Braconidae than in simple landscape. In this study, abundance of flowervisiting insects did not differ between complex and simple landscape, a similar result to Westphal et al (2008) who found landscape complexity, characterized by the proportion of semi-natural habitat, did not affect the abundance of bees. Instead, abundance of bees was more affected by the occurrence of flowering plants in the landscape.…”

“…The weather condition were predominantly clear sky, no rain, low wind and dry vegetation (Westphal et al, 2008). In each cucumber field, four transects were selected for insect sampling (Fig.…”

Invasive plant integration into native plant–pollinator networks across Europe

“…Each transect was visited three times for 135 min per transect from July to August. Therefore, for this species, the sampling effort was different for each flowering plant species (Westphal et al 2008).…”

Impact of honeybee (Apis mellifera L.) density on wild bee foraging behaviour

“…Each study site was sampled using a variable transect walk method (Westphal et al, 2008). For this method, the surveyors walked slowly among any potentially attractive resource patches and collected bees during a 120 min observational period.…”