The Impact of Secondary Metabolites in Nectar and Pollen on Bee Behavior

There are secondary metabolites in nectar and pollen known as nectar secondary compounds (NSCs). NSCs are complex chemicals influencing everything from insect foraging habits to plant reproductive success. These compounds shape the behavior of pollinators in subtle, sometimes surprising ways, impacting not only the health of individual plants but the entire ecosystem.

In this blog, we’re going to explain:

• The functions of NSCs and how they manipulate pollinator behavior, including bees.
• The different types of NSCs and their roles in plant-pollinator dynamics.
• How expanding information on NSCs may influence the future of planting and gardening.

Let’s start by covering the essential functions of NSCs.

The Function of Secondary Metabolites in Nectar and Pollen

NSCs were initially thought to play a defensive role for plants. Early studies suggested they served primarily to deter inefficient pollinators or nectar thieves, such as ants, and to protect the nectar from microbial contamination. However, newer research has uncovered a more nuanced picture of how these compounds function. 

As a research review published by MDPI explains, NSCs don’t just have defensive properties. They actively manipulate pollinator behavior, affecting how insects forage, remember floral traits, and even communicate. 

Studies have shown that these chemicals can:

• Enhance learning and memory: Pollinators are more likely to return to flowers with certain NSCs, reinforcing plant-pollinator relationships.
• Modulate foraging behavior: NSCs influence which flowers pollinators visit and how long they stay, increasing pollination efficiency.
• Affect insect physiology: NSCs can alter locomotion, sensory perception, and even arousal in insects, all of which play roles in ensuring the success of pollination.

By understanding these sophisticated interactions, farmers, gardeners, and conservationists can better appreciate the subtle but powerful impact NSCs have on pollinators.

Types of NSCs and Their Roles

NSCs come in various forms, each serving unique functions in the plant-pollinator relationship. Among the most studied NSCs are phenols, terpenoids, and alkaloids.

Phenols

Phenols can deter undesirable visitors like ants while simultaneously attracting effective pollinators. Interestingly, phenols have been found to enhance pollinator memory, making it more likely that insects will return to the same flower, reinforcing plant-pollinator fidelity.

Terpenoids

While their scents can attract pollinators, terpenoids also act as repellents for less efficient nectar thieves. Additionally, terpenoids have been shown to boost insect immunity, helping pollinators ward off diseases as they forage.

Alkaloids

These nitrogen-based compounds have potent effects on pollinator behavior, particularly learning and memory. Alkaloids also act as attractants and repellents, similar to the other two compounds we mentioned.

Together, these compounds create a dynamic system where plants can optimize pollination by shaping the behavior of their pollinators, often enhancing both plant reproduction and ecosystem stability.

Behavior-Shaping Biogenic Amines

Biogenic amines, a class of nitrogenous compounds, profoundly affect pollinator behavior. These chemicals, recently discovered in the nectar of several plant species, act as neurotransmitters that can influence everything from foraging to communication in insects, particularly bees. 

Two key biogenic amines found in floral nectar are octopamine and tyramine.

Octopamine

This compound plays a critical role in enhancing foraging and social behaviors in pollinators like bumblebees. Studies have shown that octopamine increases the likelihood of bees performing the “waggle dance,” a behavior that helps communicate the location of food sources to other colony members. 

However, octopamine also appears to make bees more faithful to specific plants, even when better food sources are available, suggesting it may shape pollination patterns in favor of certain species.

Tyramine

While less studied than octopamine, tyramine is another biogenic amine that can modify pollinator responses to food sources. Interestingly, when combined with octopamine, tyramine has been shown to reduce bees’ aversion to less desirable substances, like caffeine, hinting at a complex interaction between these chemicals.

These compounds don’t just impact honeybees; they have also been shown to affect the behavior of bumblebees, enhancing their ability to learn and adjust foraging patterns based on changing environmental conditions.

Future Research of Secondary Metabolites in Nectar and Pollen

While our understanding of NSCs has grown significantly, much remains to be explored. 

Expanding The Number of Species

Current research primarily focuses on a few key species and pollinators, such as honeybees and bumblebees. However, the effects of NSCs on a broader range of plant species and pollinators are still largely unknown. 

Expanding research to include other pollinator groups, such as birds, butterflies, flies, and solitary bees, will provide a more comprehensive picture of how these compounds influence pollination across different ecosystems.

Studying More Complex Interactions

Additionally, the majority of studies examine the effects of individual NSCs in isolation, but in nature, pollinators encounter complex mixtures of these compounds. 

Future research will focus on understanding the interactions between multiple NSCs and how these combinations affect pollinator behavior. These studies offer more realistic insights into how NSCs function in natural environments and how plants may use them to optimize pollination.

Understanding the Effect on Plants

Finally, there is a need to investigate the direct links between NSCs and plant reproductive success. 

While we know these compounds influence pollinator behavior, more research is required to confirm how this translates to improved plant fitness and long-term ecosystem stability. As climate change alters environmental conditions, the role of NSCs may become even more critical in supporting resilient plant-pollinator relationships.

Stay Up to Date with Ernst

NSCs are pivotal in shaping pollinator behavior. They go beyond simple food rewards to influence learning, memory, and foraging patterns. These compounds not only help plants optimize pollination efficiency but also contribute to the broader stability of ecosystems. 

While research has made significant strides in understanding NSCs, there is still much to uncover. As this field of study continues to evolve, further research will deepen our understanding of the complex relationships between plants and pollinators, offering valuable insights for both conservation and agriculture.

If you want to learn more now about how to support pollinators and contribute to a healthy landscape and environment, the experts at Ernst have decades of experience helping to reclaim natural landscapes across the northeastern United States.

Let us know what questions you have, or talk to us about your next landscape project.