Linking leaf economic spectrum to floral resources along an environmental gradient

Leaf and floral traits are often considered independent dimensions of the plant economic spectrum. Leaf traits are assumed to be primarily determined by abiotic factors while floral traits by biotic factors, but both are influenced by a combination of these selection pressures, suggesting that leaf and floral traits may not be completely independent. Pollen and nectar, as key floral resources for pollinators, reflect the interplay between abiotic and biotic factors. Exploring correlations between leaf traits and floral resources may offer new insights into plant strategies. To investigate the potential correlation between leaf traits and floral resources, we focused on 11 animal-pollinated species growing along an environmental gradient. We hypothesised that greater quantities of floral resources would correlate with larger values for leaf area and specific leaf area and lower values for leaf dry matter content, as this combination of traits is associated with fast nutrient use and high photosynthetic capacity, facilitating greater resource allocation for pollen and nectar production. We measured leaf traits (i.e. leaf area, leaf dry matter content and specific leaf area) and floral resources (i.e. number of pollen grains and nectar volume) in 126 individual plants and tested associations using ordination methods and correlations. We also investigated how abiotic factors (i.e. environmental selection), biotic factors (i.e. pollinator selection) and phenological traits were related to the variation in leaf and floral traits and performed a phylogenetic analysis to assess the contribution of phylogenetic signal to the main trends in variation. Our study showed a significant correlation between leaf traits and the quantity of floral resources. We found that environmental selection was the primary factor explaining the main variation in leaf traits and floral resources, while pollinator-mediated selection and phenological traits were secondarily associated with variation. The phylogenetic signal showed very little influence on the main trends in trait variation. Synthesis: Although it is generally assumed that vegetative and reproductive traits are subject to different selection pressures, our results highlight their interconnectedness and suggest that their evolution may be characterised by the balance of different selection factors rather than by independent processes.