Ants are the dominant macro-animal on Earth. There are over 12,400 species we know. Ants are almost everywhere, and wherever they are, whatever their species, they live in an astonishing array of symbiotic associations. These relationships range from gut symbioses with bacteria, to herding aphids, farming fungus, to welcoming butterfly larvae into their nests and feeding them, to planting seeds for many kinds of plants. Some ant/caterpillar behavioral symbioses are elaborate: the ants herd the caterpillars, lead them to feeding areas (pastures) and bring them inside the nest (barn) for the night. The caterpillars secrete honeydew when the ants massage them.
Many ant symbioses look purely behavioral and not obligatory. But if a symbiosis goes on long enough--say millions of years--it tends to become required for survival. For example, Pheidole ants are only found on neotropical pepper plants.
Several kinds of plants have co-evolved symbioses with ants. They are called myrmecophytes, or ant-plants. Some are trees, some vines, some are shrubs. The ants receive foods--nectar for carbohydrates plus special foods made just for ants that provide fats and proteins. The ants also receive domatia, specialized housing grown by the plants to keep their protectors close by. An ant from Borneo, Camponotus schmitzi, lives and swims in a carnivorous pitcher plant. Pheidole ants from Central America live in stems of black pepper plants, where they eat plant-grown pearl bodies. Pseudomyrmex ants from Central America live inside hollow thorns on acacia trees. Some tropical ants,such as Azeteca ants, live in Cecropia trees and fiercely attack intruders. Ant attacks persuade herbivores to quickly leave or die.
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Pheidole ants live in the hollow stem of a Costa Rican pepper plant. The white balls are pearl bodies, balls of proteins and fats the plant grows to feed the ants, a home restaurant.These ants are obligate symbionts that only live in pepper plants. In return for room & board, the ants fiercely attack every intruder, insect, mammal, bird or vine. Image credit J. Longino
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Entrance to a nest in the hollowed stem of a pepper plant. Some pepper stems are naturally hollow; others filled with soft pith easy for ants to excavate . Image credit J. Longino |
Pheidole ants living in hollow stems both vertical and horizontal. The vertical stem is ant excavated; the side branch is naturally hollow.
Image credit J. Longino |
Ants Live inside a Carnivorous Plant |
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Nepenthes bicalcarata pitcher plant vine eats insects, but its hollow tendrils are homes for tiny ants that have coevolved to be safe in the pitcher of water. |
The scary 'fangs' are really nectaries that give sweet treats to both ants and birds, whose droppings fall into the pitcher as fertlizer. |
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Camponotus schmitzi ant swims in the pitcher pool and hauls out drowned prey.The ant's feet have adapted over eons to climb safely from the pool. Image credit Michael Lo
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Camponotus schmitzi ant can navigate the slippery wax that slides other insects into the pool
Image credit Michael Lo
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Azteca Ants Protect Cecropia Trees |
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A young Azteca isthmica queen cuts into the soft tissue of a Cecropia tree to gain access to the hollow center. The trees welcome this intrusion. The resident Azteca colony founded by this queen will provide protection from herbivores, and will receive food and safe shelter.
photo and text credit Alex Wild click to his website
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Where stems join, symbiotic Azteca ants find hollows for housing. The brown objects seem to be scale insects that these ants "farm" for nectar. Sweets from scales, fats and proteins from the Cecropia tree--a good life. One tree will have many of these nest sites.
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Mullerian bodies grow pearls of ant food on a Cecropia tree. These provide fats and protein. |
Cecropia stem node grows pre-hollowed for its Azteca ant Symbionts |
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All Acacia trees grow thorns to repel herbivores, which works on mammals, but not on insect leaf-eaters or vines. So, in the tropics of the New World, a symbiosis with ants was eventually born.
Image credit Beverly Joubert
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An ant checks out the scene from its home in an adapted-for-ants acacia tree thorn. Bullhorn acacias adapted thorns to grow large enough to house ants. If a vine or epiphyte tries to colonize, the ants sting its leaf nodes with formic acid until it dies. Image credit P.Ironside
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Acacia gives ants more than thorns to live in. She feeds them sweet sap through special organs called nectaries. |
Here three ants sip nectar from nectaries on their host acacia tree. |
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| Beltian bodies grow at the tips of young acacia leaves and provide ants with fats and proteins. This incredible adaptation suggests how very long ants and acacias have been partners. |
East African whistling thorn acacias grow swollen thorn bases that attract four species of ant partners. The bases are hollow. Ant species compete for trees. The thorns whistle once ants cut an entrance hole, winds blow, and the tree becomes a huge flute. Image credit Martin Sharmin |
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Butterfly-ant symbioses have been found in two butterfly families. It is most common in the Lycaenidae. The Lycaenidae--blues, coppers, hairstreaks--make up about 30% of known butterflies, and within the family more than half of the species interlive as caterpillars with ants. The ants receive sugars and amino acids from the caterpillars. |
A remarkable mutualism has evolved between an ant, a butterfly caterpillar, and an acacia in the American southwest. The caterpillars have nectar organs the ants drink from, and the ants allow the caterpillars to eat acacia leaves. The ants provide protection for both plant and caterpillar. Photo © Gregory G. and Mary Beth Dimijian |
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| Ants "farm" aphids, tiny sapsucking insects. Ants feed on sweet nectar from the aphids, protect them from enemies, at times take them to the nest for the night, and even move them to new pastures. |
A single ant shepherd surveys a colony's herd of aphids |
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| Here ants farm mealybugs on a leaf, which secrete honeydew for the ants. |
Ant tending leafhopper larva,
as two adult leafhoppers
emerge from pupa stage below.
Amazing photo courtesy of Leon Higley
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ants tending a wood louse larva |
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ants tending a colony of leafhopper larvae |
an ant soliciting honeydew from mealybugs |
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ant tending leafhopper larva
Image courtesy Wikipedia
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ant tending a mealybug colony
Image credit Sebastien Lacau
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Dorymyrmex bicolor eating honeydew
from a barrel cactus
click to enlarge
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Dorymyrmex bicolor taking honeydew from newly molted leafhopper young
click to enlarge |
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Detail of nectary on mesquite. The nectar is seasonal--flowers need extra protection.
Click to enlarge |
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This honeypot ant is a living larder filled with honeydew to insure colony survival.
click to enlarge |
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ants on mesquite tend small sucking insects,
such as scales, for honeydew click to enlarge
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Leaf Cutter Ants Live in Symbiosis
with the Fungus They Garden |
Some ants, mostly tropical, but also some in SW desert US, farm fungus. Foragers carry leaves and stems to the nest. Gardeners lick it with anti-bacterial saliva, chew it into mushy pellets and innoculate it with strands of the fungus their species has depended on for around 25 million years. These fungi do not exist outside ant nests. Ant & fungus require each other to survive. Like most ant species, leafcutters or parasol ants have different sizes of workers in the nest. Leafcutters have tiny fierce minima workers that ride the cut leaves of foragers to protect them from parasitic flies that lay their eggs on ant necks so the larva can eat the ant's brain. |
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Trachymyrmex arizonensis in the Southwest U.S. take greens to nest, grow symbiotic fungus on it,
eat the fruiting bodies of the fungus.
click to enlarge
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The tiny swollen fruiting tips the fungus uses to reproduce via spores are like a micro-mini-mushroom. They are the primary food of
many leaf-cutting ants. |
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Huge Atta species queen on one fungus garden in her nest in Central America.
Some leaf-cutters have nests as deep as 18 feet with many millions of inhabitants.
All are the children of the queen ant. The queen is large as a mouse. Image credit Wikipedia
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Fungus farming ants have another symbiotic partner in their fungus farming. Recently, scientists discovered that the lower abdomens of gardeners were coated with anti-fungal bacteria which the gardeners use to kill invader fungi that
try to take over the fungus garden. |
busy Atta foragers on their way back to the nest |
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A mature leafcutter colony contains more than a million individual ants and can defoliate an entire tree overnight. Here a busy trail of Atta cephalotes carries cut vegetation back to the nest. Note the small ants riding atop the leaves- these minim warriors stand guard against parasitic flies attempting to attack and lay eggs in the leaf-carriers necks. Photo and text credit
Alex Wild. Click to his website
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Soil trail laid bare by the passage of millions of tiny footfalls as leafcutter ants forage for leaves to grow even more leafcutter ants to follow this same familiar trail, often hundreds of meters long, generation after generation.
Photo courtesy Ecolibrary
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Ants are the most common animal on earth, and at the same time uncommonly surprising. No creature is embedded so deeply in the fine web of relationships among species as is the ant, the master of symbiosis. Plants and ants of many species in every habitat are intertwined in life. Ants defend plants; plants feed ants.
Plants have learned that the key to ant cooperation is their stomachs. So some plants use ants to disperse their seeds and give those seeds a head start on germination. Such plants attach a treat to their seeds, called an elaiosome. These treats are rich in fats and proteins, just what a growing baby needs. Ants take the whole seed plus elaiosome back to the nest, where the eliasome is fed to ant larvae, and the seed itself is then deposited in the colony trash pile, which is rich in nutrients, a kind of compost bin. So the seed sits protected in a dark, relatively humid nutrient collection some inches below the soil surface. A great place to germinate and grow.
