Hidden Allies: The Mighty Impact of Small Ants in Ecosystems
Hidden Allies: The Mighty Impact of Small Ants in Ecosystems
Tiny insects like ants are sometimes overlooked, although they can considerably affect ecosystems. When ants have a special relationship with plants, where both benefit from each other, it is called a mutualistic relationship. According to a recent study, this ecological interaction can facilitate the growth and defense of nearby trees and increase overall productivity in ecosystems.
Staab, Michael, Pietsch, Stefanie, Yan, Haoru, Blüthgen, Nico, Cheng, Anpeng, Li, Yi, Zhang, Naili, Ma, Keping, and Liu, Xiaojuan. 2023. “ Dear Neighbor: Trees with Extrafloral Nectaries Facilitate Defense and Growth of Adjacent Undefended Trees.” Ecology 104(7): e4057. https://doi.org/10.1002/ecy.4057
Facilitation is a critical ecological process where one species increases the performance of another. For example, woodpeckers make holes in trees that later can be used as nesting places for other birds or animals. Facilitation can also occur when mutualistic relationships improve the environment for other individuals. Most plants produce nectar within their flowers, but some make it in different structures, like leaves. Plants with extrafloral nectar glands (EFNs) called nectaries have a mutualistic relationship with ants. Ants eat the sugary nectar and, in exchange, protect these trees from herbivores.
In a recent study published in Ecology, Michael Staab and his colleagues analyzed the effects of three native tree species with extrafloral nectaries in China. They assessed this investigation as part of the wider Biodiversity-Ecosystem Functioning (BEF) experiment established in 2009. The researchers look at variables such as tree growth, herbivory (leaf consumption), leaf traits, and the invertebrate community (spiders and insects). They compared these variables in two tree pairings: a non-EFN tree with an EFN tree neighbor and two neighboring non-EFN trees. Of all the data collected, the most significant finding was on biomass, meaning the total weight of all the living parts of a tree.
The authors discovered that trees growing next to EFN trees grew faster than those not paired with EFN trees. In addition, they found an increased number and abundance of ant species, which may have contributed to the decline in herbivore populations (caterpillars). A lower number of caterpillars would have allowed the trees to invest more energy in growing rather than developing chemical defenses. The findings imply that the mutualistic interaction between ants and EFN plants facilitated the growth of trees next to EFN trees.
Previous studies evaluated the facilitation effect of EFN trees on crops but not in a natural ecosystem. The authors showed that a similar facilitation effect can happen in a subtropical plantation. Trees with EFN attract more ants that can spread to trees with no extrafloral nectaries. The increased number of ants reduces the number of herbivores, raising biomass production as trees perform better.
This is just one example of how some animals, usually overlooked or considered non-consequential, can significantly impact their environment. This study highlights how mutualistic relationships between ants and plants can benefit not only the participants of this relationship but also the individuals that surround them. The mutualistic relation between ants and extrafloral nectar-producing trees can facilitate the growth of surrounding trees in a subtropical forest. The results suggest that incorporating EFN trees in tropical and subtropical restoration and reforestation in the early phase can foster tree growth and increase biomass production.