Bearing fruit: flower removal reveals the trade-offs associated with high reproductive effort for lowbush blueberry

Past studies have shown that taxa from disparate groups often respond similarly to reduced reproductive effort. These common responses imply that high reproductive effort trades off with a consistent set of other life functions for most angiosperms, albeit modulated by their growth form and life history. However, many questions remain about reproductive trade-offs in plants, including just how many other life functions they involve, how diverse these functions may be, and how the severity of these trade-offs may vary through time. To address these questions in a long-lived, iteroparous shrub, we performed flower removal on plots of lowbush blueberry, Vaccinium angustifolium (Ericaceae), over 3 years. We found significant physiological differences between removal and control plots for ten diverse traits. Vegetative phenology was shifted earlier by about 20% in removal plots, and removal plots had about 15% more vegetative biomass by mid-season as well. Removal plots produced about 10% more ripe fruit per reproductive node by harvest than control plots, and reproductive nodes in removal plots produced at least one fruit by harvest about 6% more often. While fruit water content and titratable acidity were increased by removal, other fruit traits, such as sugar content and fresh mass, were not. The strength of the removal effect varied significantly by year for seven traits; for many, such as vegetative mass/stem and ripe fruit production/node, the effect was stronger in years with more stressful abiotic conditions. Our results demonstrate that there are tangible but variable costs to high reproductive effort for flowering plants.