Ecological Archives E096-192-A3
María C. Rodríguez-Rodríguez, Pedro Jordano, and Alfredo Valido. 2015. Hotspots of damage by anatgonists shape the spatial structure of plant–pollinator interactions. Ecology 96:2181–2191. http://dx.doi.org/10.1890/14-2467.1
Appendix C. Description of the methodology used to estimate plant characteristics.
Methods
For each individual plant, we measured its height and two variables related to animal reward: floral nectar production and nectar sugar concentration.
Plant height (cm) was measured as the distance from plant base to the tip of the highest inflorescence. We used this biometric variable as a surrogate of floral display because it was positively correlated with the number of inflorescences (Spearman’s rank correlation, rs = 0.69, P < 0.001) and total number of floral pedicels (rs = 0.61, P < 0.001).
For the estimation of floral nectar production and nectar sugar concentration, we selected a subset of flowers located at basal positions in the inflorescences that we depleted and bagged during 24h (n = 790 flowers, range: 5-31 flowers/plant). In each flower, we used 50-μL microcapillary tubes to probe the corolla base until no more nectar could be removed. Then, we measured with dial calipers the distance nectar had migrated up the tubes and converted it to volumes (μL). We spotted the nectar within the tubes on a handheld refractometer (Bellingham & Stanley Ltd, Tunbridge Wells, Kent, UK) to record its sugar concentration (w/w% of sugar equivalents). Calculated over all flowers analyzed in the plant, we defined nectar volume as the average number of microliters produced per flower (μL/flower), and nectar sugar concentration as the average percentage of sugar per flower (w/w% sugar/flower).