Floral nectar is a vital energy resource for pollinators. Although nectar volumes and sugar concentrations have been quantified for many species of flowering plants, many questions remain regarding sources of intraspecific and interspecific variation, including the effects of abiotic factors, such as temperature and precipitation, on community nectar production. Many of these abiotic factors are being altered under climate change, limiting our ability to predict the availability of this important resource for the species that depend on it. To help address this knowledge gap, we quantified nectar resources for the majority of pollinator-visited flowering species in subalpine meadows varying in water availability. This allowed us to: (1) quantify interspecific variation in nectar resources for 22 pollinator visited plants, (2) compare nectar resources between wet and dry meadow habitats, and (3) examine intraspecific variation across years.
Results/Conclusions
We observed considerable variation in nectar traits (volume and sugar concentration) across our survey of 22 pollinator-visited subalpine plants. Nectar volume ranged from 0 μl to 51.2 μl per flower, with a mean of 1.4 μl for flowers with nectar, and nectar sugar concentration ranged from 0.06 mg/μl to 1.1 mg/μl, with a mean of 0.5 mg/μl. When comparing community nectar traits across wet and dry meadows for the entire summer growing season, we observed that nectar volume and concentration were overall greater in wet meadows. However, when looking at finer time scales, we observed that dry meadows had greater means for nectar traits in early summer; wet and dry meadows had similar means for nectar traits during mid-summer; and wet meadows had considerably greater means for nectar traits during late summer. When comparing nectar traits across years, we found that nectar volumes were higher and nectar sugar concentrations were lower in a wet year (2019) compared to a drought year (2018) for the majority of species considered. Taken together, this research provides an image of the nectar resource landscape, and how this resource landscape may respond to future climate change.