High rates of nectar depletion in summer grasslands indicate competitive conditions for pollinators

Competition among pollinators for floral resources is a phenomenon of both basic and applied importance. While competition is difficult to measure directly under field conditions, it can be inferred indirectly through the measurement of floral resource depletion. In this study, we conducted a pollinator exclusion experiment to calculate nectar depletion rates in summer across 16 grassland sites in the German regions of Franconia and Saxony-Anhalt. Overall depletion rates were estimated at 95% in Franconia and 79% in Saxony-Anhalt, indicating strong nectar limitation and likely competition among pollinators for nectar. Despite being ubiquitous in our study regions, honey bees were scarce at our sites at the time of nectar sampling. This demonstrates that wild pollinators alone are capable of massive nectar depletion, and the addition of managed honey bees to wild pollinator communities may intensify already competitive conditions. Nevertheless, the manifest diversity of the pollinator co..., Our study was set in the German regions of Franconia and Saxony-Anhalt **(Figure 1A)**. In each region, we selected eight semi-natural grassland sites for sampling, ranging in size from 0.1 to 32.0 hectares in Franconia and from 2.3 to 12.5 hectares in Saxony-Anhalt. The sites in Franconia were calcareous grasslands, while those of Saxony-Anhalt were set in the distinctive porphyry substrate of that region and ranged from 2.3 to 12.5 hectares. In both regions, semi-natural grasslands are highly fragmented and embedded in a predominantly agricultural matrix characterized by field crops, vineyards (in Franconia), deciduous forest patches, and small settlements. Neighboring sites were separated by a minimum of 2.6 km in Franconia and 5.7 km in Saxony-Anhalt.
Sampling protocols differed across regions to accommodate local floristics and field work logistics. In Franconia, we sampled from 4-19 July, 2022. On each sampling day, we arrived at a given site around sunrise (5:00-6:00), prior to t..., , # High rates of nectar depletion in summer grasslands indicate competitive conditions for pollinators

## [https://doi.org/10.5061/dryad.sf7m0cgf7](https://doi.org/10.5061/dryad.sf7m0cgf7)

## Description of the data and file structure

All data files are provided in `.rds` format for convenient handling in `R` (and to avoid any nasty tricks Excel might try to play with a regular spreadsheet file). To load an `.rds` files into your `R` environment as a data frame, use the `readRDS()` command. Data frames can easily be exported to `.csv` format using `write.csv()`. Each `.rds` data file is used in one or more of the accompanying RMarkdown files listed in the Code/Software section.

### `wue_nectar.rds`

Nectar sampling data from Lower Franconia; 13 columns

1. `site_name`: Name of sampling location; a grassland site
2. `date`: Date of sampling
3. `species`: Species of sampled flower
4. `genus`: Genus of sampled flower
5. `plant`: Individual plant to which sampled flower belonged
6. ...