What are extrafloral nectaries?
When you study insects, or even birds for that matter, you start to understand you have to get to know plants a bit too. It’s all connected.
Plants (including trees and shrubs) provide food and shelter for many different species of animals. Admittedly, I just don’t know a lot about the parts of plants, beyond things like a tree trunk, bark, limbs, branches, leaves, or stems or flowers, nuts, fruit. The obvious parts.
There are some not so obvious parts. Like these extrafloral nectaries. Huh? Sounds weird. Keep reading.
Extrafloral nectaries (EFN’s) are glands occurring on more than 2000 plant species in 64 families. Extrafloral literally means outside of the flower. When we think of nectar, we usually think of little bees and hummingbirds flying around, visiting pretty flowers to sip nectar and in the process, pollinate all of our plants. It’s just that plants are a bit more complex. These glands are located in various places on plants (including trees and shrubs), and may be found on the laminae of leaves, petioles, rachids, bracts, stipules, pedices, fruit, etc. (Mizell, 2019).
These glandular secretions are a fascinating part of how plants attract and sustain a diverse, ecological community, providing sustenance for a multitude of species, including both pests and predators. You can find ants, aphids, beetles (including ladybugs), bees, wasps, and possibly even birds utilizing this excretory faucet to sip what consists of mostly carbohydrate-rich sugar, but also comprised of a wide array of amino acids and other nutrients.
Why are these important? Well, scientists are still trying to fully understand all of the diverse relationships around extra-floral nectaries. It is thought perhaps, beyond attracting organisms to a food source, they play a role in orchestrating a plant’s defense strategy against predators. They also are believed to provide a source of food and/or beneficial nutrients for various organisms during the off-season – when flowering and pollen sources are not available. They may also reduce conflict between ants and other pollinators by partitioning resources (Villamil & Stone, 2019).
Bentley, B. L. (1977). Extrafloral nectaries and protection by pugnacious bodyguards. Annual Review of Ecology and Systematics, 8(1), 407-427.
Holopainen JK, Blande JD, Sorvari J. Functional Role of Extrafloral Nectar in Boreal Forest Ecosystems under Climate Change. Forests. 2020; 11(1):67. https://doi.org/10.3390/f11010067
Mizell, R. 2019. MANY PLANTS HAVE EXTRAFLORAL NECTARIES HELPFUL TO BENEFICIALS. UF IFAS Extension Bulletin. https://edis.ifas.ufl.edu/publication/IN175
Villamil, N., Boege, K., & Stone, G. N. (2019). Testing the Distraction Hypothesis: Do extrafloral nectaries reduce ant-pollinator conflict?. The Journal of ecology, 107(3), 1377–1391. https://doi.org/10.1111/1365-2745.13135