Sweet signals: Using floral traits to predict nectar sugar availability
Floral nectar is a key energy resource for many animals, yet its availability remains poorly quantified across plant communities. We tested whether floral traits can predict nectar rewards across diverse floras. We analysed relationships between floral morphology and nectar traits in 156 flowering plant species from temperate and tropical regions. Nectar volume, sugar concentration, and total sugar content were measured, and linear mixed-effects models were used to assess floral trait-nectar relationships in tubular and non-tubular flowers. Phylogenetic signal was evaluated using Blombergs K and Pagels {lambda}. Nectar volume increased strongly with corolla size in both floral types. Total sugar content scaled approximately 1:1 with nectar volume despite variation in sugar concentration, indicating that sugar reward is driven primarily by nectar volume. Floral morphology consistently predicted nectar rewards across floras, whereas phylogenetic relatedness explained relatively little variation. These findings provide a scalable framework for estimating floral sugar resources across landscapes.