Data: Measuring plant attractiveness to pollinators: methods and considerations

Global pollinator declines have fostered increased public interest in creating pollinator-friendly gardens in human-managed landscapes. Indeed, studies on urban pollinator communities suggest that flower-rich greenspaces can serve as promising sites for conservation. Ornamental flowers, which are readily available at most commercial garden centers, are ubiquitous in these landscapes. These varieties are often non-native and highly bred, and their utility to pollinators is complex. In this study, we used observational data and citizen science to develop a methods framework that will assist stakeholders in the floriculture industry to incorporate metrics of pollinator health into existing breeding and evaluation protocols. The results of this study support how plant attractiveness to pollinators is often dependent on variables such as climate and plant phenology, which should be considered when developing an assessment tool. Furthermore, we found that some cultivars were consistently attractive across all observations while for other cultivars, pollinator visitation was apparently conditional. We determine using multiple statistical tests that 10 min is a sufficient length of time for observation of most plant types to broadly estimate three measures of plant attractiveness: visitor abundance, primary visitors attracted, and cultivar rank attractiveness, without sacrificing efficiency or accuracy. Additionally, we demonstrate that properly trained non-expert observers can collect accurate observational data, and our results suggest that protocols may be designed to maximize consistency across diverse data collectors. 

Methods
This study includes two different datasets. The first is the dataset (A) was used to determine the minimum amount of time needed to observe a single plant to obtain accurate metrics of pollinator visitation. This data was collected by a single individual (E. Erickson), who observed a plant in the field for 30 minute increments and recorded the time the each individual visitor arrived at that plant and the taxonomic order of that visitor. The second dataset (B) was used to quantify how unique observers differed in the flower visitors they recorded on plants. Novice and experienced observers were each given unique data sheets that were either descriptive (insect morphotaxa) or simple (insect orders). Each observer watches a single plant replicate for 10 minutes and all observers observed a representative replicate of each cultivar in the study. Separate observers were used for the container annual and the in-ground perennial trials. 

Floral area measures were calculated by first photographing each cultivar in birds-eye-view with a meter stick held at the crown of the plant and calculating the area in bloom based on user defined pixel measurements in Adobe Photoshop 

All data analyses were conducted in R, and the code is included in this data archive.