Acacia Tree Ants
This month's mutualism is the relationship between the whistling-thorn Acacia drepanolobium and its body guard ants which protect it from the. Ants and Trees: A Lifelong Relationship. An American carpenter ant licks sugary nectar off the surface on an oak gall. Credit: Aaron M. Ellison. The relationship between acacia and ants is an example of mutualism. The following ScienceStruck article discusses the acacia-ant connection in detail.
Some people are used to summer and winter seasons, but many places in the world have a rainy season and a dry season instead.
Ants protect acacia plants against pathogens
Many trees that live in these places have leaves during the rainy season and reduce the number of leaves during the dry season, just as some trees do in the winter. If a tree goes through the dry season without leaves, it has to use the food it made in the leafy rainy season.
If the dry season is very long compared to the rainy season, the tree may run out of food and die. But this potential danger can be avoided with the help of ant aides. The experiments were conducted in Mexico and parts of Central America. Click the image to enlarge and learn more. As anyone who's ever stuck their hand in an ant nest will know, ants are good at defending themselves.
A colony of ants has many individuals, and all of them can bite. In tropical countries where it is warm all year, some trees have developed special relationships with defending ants. Ants live inside the tree, and they defend the tree against insects that eat the leaves. It's a good deal for both the trees and the ants.
So, we know that ants defend leaves, and leaves are most important to trees when conditions are dry. Scientists then asked, is leaf defense by ants better when trees live in dry places? To answer this question, the scientists looked at trees and ants in dry places and wet places.
In all these places, they measured how good the ants were at defending their tree home. Ants defended leaves better under drier conditions. This means that trees survive more in dry places because their ants protect their food supply. This is a perfect deal for trees.
But, the scientists wondered, can the trees actually encourage their ants to be better defenders when conditions are dry? Ever heard of a scale insect?
Ants protect acacia plants against pathogens | Max-Planck-Gesellschaft
These weird little insects are like plant vampires. The sugars that plants make in photosynthesis move around the plant as sap in special tubes.
The scale insects insert their mouths into these tubes and suck the sap. Insects are animals, and like all animals, they use some of what they eat to grow and make babies, and they poop out the rest. Plant sap has more sugar than the scale insects can use, so scale insects poop sugar.
This makes them a favorite of ants, which can't drink plant sap straight from the plant, but love sugar. That's right, the ants eat the sugary poop from the scale insects. When ants live inside trees, they often have herds of these sugar-pooping scale insects. It's a lot like people having herds of cows for milk. We can move our cows around a pasture, but the amount of milk we'll get depends on how much grass is growing in the pasture.
In the same way, the ants can move their scale insects around the tree, but the amount of sugar that the ants get depends on the tree. Trees Trade in Sugar The scientists found that trees in drier places had more scale insects for ants. Does the tree provide more food for ants in drier places to get better defense for their valuable leaves? The scientists answered this question by using math to ask what the trees should do with their sugar under different conditions.
They found that trees at drier sites should provide more sugary food to defending ants to avoid losing leaves and dying from starvation. Trees at wetter sites should use their sugars for growth instead of giving them away to the ants. Ants tending their scale insects. Much like keeping a heard of cows, these ants keep scale insects for their sugar poop that they use for food. Ant Insurance If your parents have a car, they buy car insurance.
Scientists at the Max Planck Institute for Chemical Ecology have now looked more deeply into the insect-plant interaction, asking whether the tiny bodyguards also provide protection against microbial pathogens. They compared the leaves of acacia plants which were inhabited by either mutualistic or parasitic ants to leaves from which ants had been removed. Intriguingly, the leaves of acacia colonized by parasitic ants showed more leaf damage from herbivores and microbial pathogens than did the leaves that had mutualistic ants.
Analysis of the surfaces of the leaves revealed that the number of plant pathogens as well as of necrotic plant tissues increased considerably when mutualistic Pseudomyrmex ferrugineus ants were absent. These plants also showed strong immune responses in the form of an increased concentration of salicylic acid, a plant hormone which regulates defence against pathogens. Detailed analysis of the bacterial composition on the surfaces of the leaves suggested that the presence of mutualistic ants changed the bacterial populations and reduced harmful pathogens.
Although far less pronounced, this effect could also be observed in parasitic ants. Pseudomyrmex ferrugineus protects the Acacia with its bacteria from pathogens. Plant pathogen Pseudomonas syringae was sensitive to the application of leg extracts of both ant species and its growth was inhibited. In the next step, the scientist isolated and identified bacteria from the legs of the ants.
In lab tests, bacterial strains of the genera Bacillus, Lactococcus, Pantoea and Burkholderia effectively inhibited the growth of Pseudomonas bacteria isolated from infected acacia leaves.
Interestingly, some of the bacterial genera associated with the ants are known to produce antibiotic substances.