Symbiosis exists between the ant. A wonderful symbiosis: ants and plants. Crocodile and plovers

Botanists from the University of Munich studied the evolution of symbiosis between ants and myrmecophilous plants from the group Hydnophytae, forming special growths of tissues - domatia, in which these insects settle, providing in return to their hosts nutrients. This mutually beneficial cooperation appears to be original to this group of plants, but has been lost several times during evolution. The study results confirmed several existing theoretical predictions. First, the return to non-symbiotic life occurs only in unspecialized plants that have not developed a strict connection with a specific species of ant. Secondly, the loss of symbiosis occurs under conditions of low abundance of ant partners, and not due to the loss of the need for it. Thirdly, after the loss of connection with ants, the morphological evolution of domatia accelerates, freed from the action of stabilizing selection that preserves them in symbiotic species.

Mutually beneficial cooperation - mutualism - is now often considered by coevolution specialists as one of the main mechanisms for increasing the complexity and maintaining the stability of ecosystems. Here it is appropriate to recall the symbiosis higher plants with fungi (mycorrhiza) and nitrogen-fixing bacteria, which largely determined the very possibility of successful settlement of land, and a huge number of animals that digest food with the participation of protozoa and bacteria. While not as close (now called symbiotic) as in the examples above, mutualism between plants and pollinators, as well as between plants and seed-dispersing animals, is also quite important for the functioning of ecosystems. After all, mitochondria and chloroplasts, necessary for the development of complex multicellular organisms, are descendants of bacteria that have completely lost the ability to free life and became organelles.

Guillaume Chomicki and Susanne S. Renner from the University of Munich decided to investigate the reasons for the loss of mutualism using the example of ant-plant symbiosis (see Myrmecophytes). The authors focused on plants from the subtribe Hydnophytinae; some of them are used as ornamental plants of the Rubiaceae family. These epiphytic plants, native to Australasia, provide ants with a place to build nests by forming special hollow structures on the stem - domatia, and the insects supply the plants with nutrients from their excrement and the "garbage" they bring. This mutualism can be either specialized, in which one plant species is inhabited by one specific species of ants (the entrance to the domatia is precisely adjusted to the size of an individual of this species), or unspecialized (generalized), when one plant species can be inhabited by different species of ants. In the above-mentioned group of plants there are both of these variants and, in addition, some species do not interact with ants at all (Fig. 1). A total number species (105) provides sufficient material to test theoretical predictions.

1) Is the loss of mutualism associated with one or another ancestral state (specialized or generalized)?

2) Is the loss of mutualism associated with certain environmental conditions(e.g. ant rarity or nutrient availability)?

3) Does the loss of mutualism affect the rate of evolution of the entrance to the domatia (while the plant interacts with ants, stabilizing selection should act on this trait, reducing variability, but after the loss it should disappear).

The authors compiled a phylogenetic tree based on six plastid and nuclear genes (Fig. 2), sequenced in 75% of the 105 species of the subtribe, and using two statistical methods (maximum likelihood estimation, see Maximum likelihood and Bayesian analysis, see Bayesian inference) found that, contrary to their expectations, the initial state for this group of plants was an unspecialized symbiosis, which was subsequently lost about 12 times (this tree is only an approximate reconstruction of the actual evolutionary history, so the resulting value may not be accurate). To further confirm the initial presence of symbiosis, the authors conducted a phylogenetic analysis in which they artificially set the absence of symbiosis in the common ancestor of all hydnophytes - and this model built the tree significantly worse.

Eleven of the twelve cases of symbiosis extinction occurred in non-specialized lineages. The only exception is the genus Anthorrhiza, for which the ancestral state could not be determined with certainty.

17 of the 23 species that do not enter into symbiosis with ants live in the mountains of New Guinea at an altitude of more than 1.5 km. It is known that the diversity and abundance of ants decreases as one ascends the mountains - this trend is also observed on this island. Moreover, in three of these species rainwater accumulates in domatia and frogs live (Fig. 1, D), six species can obtain nutrients from the soil, but this is also true for two species that maintain a specialized relationship with ants. All these facts speak in favor of the hypothesis that the reason for the loss of mutualism is not the loss of the need for it, but the lack of potential partners. This also explains the absence of cases of loss of contact with ants in specialized types: Having lost a partner, they simply die out.

Since the specialized myrmecophiles among the Hydnophytinae interact with ants of two genera of the subfamily Dolichoderinae, found at different altitudes, while the generalists interact with more than 25 unrelated species whose diversity decreases with altitude, the authors suggested that if the partner-scarcity hypothesis is correct, both main reason loss of mutualism, then generalists should be found mainly at low altitudes, the distribution of specialists should not depend on altitude, and plants that have lost mutualism should be found mainly in the mountains. Several independent statistical analyzes confirmed these expectations (Fig. 3).

What happens to domatia after the loss of mutualism? Theoretical predictions say that as long as the symbiosis exists, the size of the entrance to them, which allows the plant to “filter out” the desired ants, is subject to stabilizing selection, maintaining the optimal size. Moreover, among specialists this selection should be stronger, that is, the rate of evolution should be minimal. And after the plant has stopped interacting with ants, selection should weaken, which will lead to an increase in the rate of change in this trait.

The size of the entrance hole in the domatia varies significantly among hydnophytes: from a millimeter to more than 5 centimeters. Analysis of the distribution of these sizes between species showed that many non-mutualistic species have large openings - through them large invertebrates (cockroaches, centipedes, peripatus, spiders, slugs and leeches) and even small vertebrates (frogs, geckos and skinks) can penetrate into the domatia. The resulting estimate of the rate of evolution of the hole diameter is also consistent with the hypothesis: for specialists - 0.01 ± 0.04, for generalists - 0.04 ± 0.02, for non-mutualists - 0.1 ± 0.02 (values ​​in arbitrary units, cm D. L. Rabosky, 2014. Automatic Detection of Key Innovations, Rate Shifts, and Diversity-Dependence on Phylogenetic Trees).

However high speed The evolution of the size of the entrance hole of domatia can also be explained by the fact that in the absence of communication with ants, selection occurs that favors the penetration of larger animals inside. However, there is currently no evidence that these residents benefit the plant, although this possibility requires further study.

Finally, the authors showed that as one moves into the mountains, average speed morphological evolution of Domatacian apertures - to do this, they developed a method that combined data on phylogeny and species distribution, which allowed them to obtain a “morphological evolution map” (Fig. 4).

This research did not reveal anything completely unexpected, but that does not make it any less valuable. After all, theoretical predictions must be tested on “living” material. The authors were lucky to find a good subject for research. Let's hope that other similar works will follow, which will make it possible to understand how often certain scenarios for the evolution of mutualism are realized.

Source: G. Chomicki, S. S. Renner. Partner controls abundance mutualism stability and the pace of morphological change over geologic time // PNAS. 2017. V. 114. No. 15. P. 3951–3956. DOI: 10.1073/pnas.1616837114.

Sergey Lysenkov

Anyone who is interested in gardening, growing vegetables, various fruits, berries, herbs and flowers, in general - everything that can be grown in a garden plot, they know that if ants appear on a plant, it means that aphids will soon appear. And this is not surprising. These insects “take care” of each other and help them survive in such a difficult and unsafe world. Let's take a look at how the symbiosis of aphids and ants is organized.

A short excursion into the life of ants

Ants are one of those few insects that are almost constantly in search of food for their ant queen and her offspring. In nature, there are approximately 12,000 species of them and all of them belong to the family of social insects. This means that they live in large individual colony families, for example, like termites.

The diet of ants consists of food rich in carbohydrates and proteins. They can safely be called a sweet tooth, and if you don’t take into account human food, which they happily “steal” and absorb, then their favorite delicacy that they can get in nature is honeydew, produced by aphids, scale insects, scale insects.

The hierarchy in the ant community is structured very simply and correctly. One family-colony of ants lives in one anthill. This is a kind of society in which everyone has their own role. The queen is the leader of this community. Its only function is to give birth to offspring. And worker ants take care of this “mother of many children” and her children. They are asexual, their main function is to search for food. In search of food, they can overcome all possible obstacles (except insecticides) and go quite far from their anthill or nest. There are also ants - soldiers. They perform the corresponding function - they guard and protect their anthill. It's simple!

Information from the life of aphids

In addition to the ability to damage plants purely mechanically, aphids can transfer to plants various diseases- viral and fungal, for example - sooty fungus. With this disease, the leaves become covered with an unpleasant sticky liquid, disrupting all vital physiological manifestations in the tissues of the affected plant.

The essence of the symbiosis between aphids and ants

The relationship between ants and aphids is very similar to the relationship between humans and productive farm animals. The ants “take care” of the aphids, and in return they receive sweet honeydew, which they simply adore.

Looking from the outside at the accumulation of a bunch of aphids in one place, surrounded by ants, the association with grazing a herd of cows really comes to mind. But this is not entirely true. In fact, aphids, like herd animals, always feed in the company of their “relatives”, and where there is more than enough food, a very decent number of these “sweet producers” can “feast”. Ants always come to such “herds” to feast on honeydew. Therefore, it seems that the ants are herding aphids.

Sometimes it happens that an ant is not averse to snacking not only on the honeydew, but also on the aphids themselves. Manifestations of such symbiosis are expressed:

• In genuine “guardianship” of aphids by ants. These are fences built around aphids from small particles of plants held together with sand, very reminiscent of corrals for cows. Although the real reason Such concern among ants lies in a banal sense of ownership of aphids, like any other food.
• "Grazing" of aphids by ants. In fact, the actions of ants that resemble “grazing” are normal communication. Ants “talk” to their own kind through their antennae and the exchange of fluids.
• Transferring aphids to a specific place, where “grazing” will later take place, is a safety measure. Ants do the same with their fertilized eggs and already hatched larvae.
• Selected species ants learned to store honeydew for future use. However, not only her. The method of storing honeydew is very original - inside itself. As a result of many years of effort, such reservoir ants have greatly developed a goiter, like the muscles of an athlete - a bodybuilder. Every ant has a goiter, as an anatomical part of the body, but it is developed only in those who retain a supply of fluid. The abdomen of such an ant swells so much that any movement becomes almost impossible. As a result, the life of such a living “tank” takes place purely inside the anthill and is intended exclusively for the benefit of all other members of the colony. This is such sacrifice.
• Since ants love to eat honeydew, they have learned to “milk” aphids at any convenient time. For this you only need to “tickle” the aphids!
• From such a symbiosis, the aphid receives reliable protection and care, in which nature has infringed upon it. Ants reliably protect their charges from the encroachments of various ladybugs, lacewings, mites, birds and other entomophages wanting to feast on aphids. Sometimes you even have to “fight” with “foreign” ant invaders.

When attacking the entrusted “herd,” the ants even help the aphids remove their proboscis from the plants, drive them to a safe place, and sometimes carry them in their jaws. The grateful aphid, in order not to interfere with the savior’s movement at such a crucial moment, tucks its paws and does not move.

• This is how ants work throughout the summer, carrying their “nurses” from plant to plant, from leaf to leaf. In the fall, they place aphids in their anthills so that they spend the winter in comfort and do not freeze. Even the eggs of aphids in ants undergo careful and careful care.
• But ants also regulate the number of aphids. If the population is too large, the ants destroy some of them.
• Sometimes, when moving to a new habitat, ants take their aphids with them.

Here is a wonderful video where you can see an ant “begging” for sweet honeydew from an aphid (if the language is not clear, you can turn off the sound):

Based on everything that was written earlier, it becomes obvious that when defending against aphids, there is no need to rush at the ants. And remember that aphids are the source of sweet honeydew, which attracts more than just ants. If it is not present in your garden lands, then the risk of other sweet-hunting insects will be much lower. For today, this is all that gardeners need to know about the symbiosis between aphids and ants.

Wonderful symbiosis

The nature around us sometimes demonstrates such unusual forms of cooperation between animals and plants that even biologists throw up their hands in surprise. One of the most surprising manifestations of symbiosis is the relationship between different species of tropical ants and the plants on which they live. Unfortunately, in our temperate latitudes, you will not find examples of such a community, but in the tropics the so-called myrmecophilous plants are very numerous and diverse. They may refer to different systematic groups, but on environmental grounds they are often combined under common name"ant trees" These plants literally provide their residents with both a table and a home. And the ants, in turn, not only collect various insect pests from them, but also protect them more reliably from herbivorous mammals than the sharpest and most numerous thorns.

The simplest example of such cooperation is the relationship between some South American ants and plants from the bromeliad order(Bromeliales). In the floodplain forests of the Amazon and its tributaries, the level of flood waters often rises by several meters, so that ants simply cannot live on the ground and they have to create shelters for themselves on the “upper floors” of the tropical forest. While there is no flood, the ants diligently drag pieces of soil onto the trunks, which they glue together with special secretions, creating solid foundation nests Along with the soil, the ants also bring seeds up various plants, including bromeliads, which find favorable conditions in the hanging nest being constructed and quickly germinate. It is interesting that their roots do not destroy them, but, on the contrary, hold the nest together. Moreover, the roots of bromeliads cover the trunk of the host tree with a strong ring, creating an additional frame for the ant house. It should be noted that such a symbiosis is not the privilege of bromeliads - other tropical epiphytes, which are often called “ant epiphytes,” can also develop in this way. The resulting structures as a result of their growth are beautiful name"hanging ant gardens"

"Ant garden" in the tropical wetlands of the Amazon Basin

The second version of the symbiosis between plants and ants can also be found on the banks of the Amazon, where numerous trees from the Melastomataceae family grow. On top surface leaves of many species of these trees, on their leaf petioles or on the stem under the petiole you can see large swellings - double bubbles separated by a longitudinal partition, opening outward with small holes. In these hollow swellings, called formicaria (from the Latin word Formica - ant), small, but very painfully biting ants settle, which, in gratitude for the provided home, protect the plant from various pests, and most importantly, from leaf-cutter ants, which are capable of " agricultural needs for short term completely remove leaves a big tree. Locals They also avoid touching plants that carry “ant bags”, since as soon as you shake them slightly, indignant insects get out of their shelters and attack the troublemakers.

“Ant bags” on the leaves are found not only in representatives of the Melastoma family, but also in plants from other groups. For example, some vines from the swallow family (Aslepiadaceae) make excellent houses from leaves. Some of them have rounded leaves, arranged in two rows along the stem, arched and pressed tightly against the bark of the host tree. In the axils of such leaves, roots develop, which not only firmly hold the leaf in place, but also absorb moisture and nutrients, giving life to the entire vine. Under such pocket leaves, excellent living conditions are created for ants, who happily settle there.

Even more amusing shelter houses are given to ants by another liana from the family of swallowtails - Rafflesiana (Dischidia rafflesiana), which grows in South-East Asia. This vine usually bears leaves of two types: fleshy, rounded and modified into peculiar bags or jugs, formed by leaf blades folded on the underside and fused along the edge. At the upward-facing base of such a leaf there is a rather wide hole, bordered by a ridge, into which a highly branched aerial root enters. This root absorbs water that enters the pitcher and also serves as an excellent ladder for the ants that often take up residence in these funny natural tents.

Task 1. Write down required numbers signs.

Signs:

1. They consist of complex organic and inorganic substances.

2. Assimilate solar energy and form organic matter.

3. They feed on ready-made organic substances.

4. Most representatives reproduce only sexually.

5. Metabolism and energy occur in the body.

6. The essential elements of cells are: cell wall, chloroplasts, vacuoles.

7. The vast majority of representatives actively move.

8. Grow throughout life.

9. Constantly adapt to environmental conditions.

Signs of all organisms: 5, 9.

Plant characteristics: 2, 6, 8.

Signs of animals: 3, 4, 7.

Task 2. Fill out the table.

Task 3. Mark the correct answer.

1. Symbiosis exists:

a) between an ant and an aphid.

2. Tenancy exists:

b) between the sticky fish and the shark’s body.

3. If the number of prey increases, then the number of predators:

c) first increases and then decreases along with the number of victims.

4. Largest number There are:

a) in the class of insects.

5. Animals differ from plants:

c) way of eating.

6. Of the listed animals, the following live in two environments:

b) field mouse;

c) ladybug.

7. Destroyers of organic substances are:

b) molds.

8. Most effective way conservation of wildlife is:

c) adoption and mandatory compliance with effective laws on the protection of wildlife.

9. The main importance of producers in nature is that they:

b) form organic substances from inorganic ones and release oxygen.

10. The white hare and the brown hare are classified as different types, because they:

b) have significant differences in appearance.

11. Related genera of animals are combined:

b) into families.

12. All living organisms are characterized by the following characteristics:

b) breathing, nutrition, growth, reproduction.

13. The sign on which the statement about the relationship of animals and plants is based:

b) eat, breathe, grow, reproduce, have a cellular structure.

b) use other animals as a habitat and source of food.

Task 4. Fill in the gaps in the text.

Between organisms in a biological community there are established food and trophic communications. again the food chain are autotrophic organisms. They use solar energy to form organic matter from carbon dioxide and water. The producers feed on herbivores, which in turn are eaten by predatory animals. Animals are called heterotrophic organisms. Destroyer organisms (bacteria, bacteria, etc.) decompose organic substances into inorganic ones, which are again used by producers. The main source of energy for the circulation of substances is sun, air and water.

Task 5. Write down the necessary numbers of the names of organisms from the list.

Names of organisms:

1. Earthworm.

2. White hare.

5. Wheat.

6. White clover.

7. Dove.

8. Bacteria.

9. Chlamydomonas.

Producers of organic substances: 5, 6, 9.

Organic consumers: 2, 4, 7, 10.

Organic Destroyers: 1, 3, 8.