Plant species with larger extrafloral nectaries produce better quality nectar when needed and interact with the best ant partners

Few studies have explored the phenotypic plasticity of nectar production on plant attractiveness to ants. Here, we investigate the role of extrafloral nectary (EFN) size on the productivity of extrafloral nectar in three sympatric legume species. We hypothesized that plant species with larger EFNs (i) have higher induced nectar secretion after herbivory events, and (ii) are more likely to interact with more protective (i.e. dominant) ant partners. We target 90 plants of three Chamaecrista species in the field. We estimated EFN size and conducted field experiments to evaluate any differences in nectar traits before and after leaf damage to investigate the phenotypic plasticity of nectar production across species. We conducted multiple censuses of ant species feeding on EFNs over time. Plant species increased nectar descriptors after leaf damage, but in different ways. Supporting our hypothesis, C. duckeana, with the largest EFN size, increased all nectar descriptors, with most intense post-herbivory-induced response, taking its place as the most attractive to ants, including dominant species. EFN size variation was an excellent indicator of nectar productivity across species. The higher control over reward production in plants with larger sized EFNs reflects an induction mechanism under damage that reduces costs and increases the potential benefits of indirect biotic defences. Plant species with larger extrafloral nectaries were more productive, had higher induced extrafloral nectar secretion after herbivory, and interacted more with many more protective ant species.

Automated summary

This study investigates the phenotypic plasticity of nectar production in relation to plant attractiveness to ants. The researchers examined the impact of extrafloral nectary (EFN) size on extrafloral nectar productivity in three sympatric legume species. It was found that plant species with larger EFNs had higher induced nectar secretion after herbivory events and interacted more with dominant ant partners. The results suggest that EFN size variation is an important factor in determining nectar productivity and interactions with protective ant species.