How ants and aphids interact with each other. How do ants and aphids interact with each other? Crocodile and zoo

Botanists from the University of Munich studied the evolution of the symbiosis between ants and myrmecophilous plants from the group of Gidnofitovye, forming special tissue growths - domination, in which these insects settle, providing nutrients in return to the owners. This mutually beneficial cooperation, as it turned out, is the starting point for this group of plants, but was lost several times during evolution. The results of the study confirmed several existing theoretical predictions. Firstly, a return to non-symbiotic life occurs only in non-specialized plants that have not developed a strict relationship with a specific species of ants. Secondly, the loss of symbiosis occurs in conditions of a low abundance of ant partners, and not due to the loss of need for it. Thirdly, after losing contact with ants, the morphological evolution of domocians, freed from the effect of stabilizing selection, which preserves them in symbiotic species, accelerates.

Mutually beneficial cooperation - mutualism - is now often considered by experts on co-evolution as one of the main mechanisms of complicating and maintaining the sustainability of ecosystems. It is appropriate to recall the symbiosis of 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. Not so close (it is now called symbiotic), as in the above examples, the mutualism of plants and pollinators, as well as plants and animals propagating seeds, is also very important for the functioning of ecosystems. In the end, the mitochondria and chloroplasts necessary for the development of complex multicellular organisms are the descendants of bacteria that have finally lost the ability to live freely and become organelles.

Guillaume Chomicki and Susanne S. Renner from the University of Munich decided to investigate the causes of the loss of mutualism using the symbiosis of ants and plants (see Mirmecophytes). The authors dwelled on plants from the subtribe Hydnophytinae; some of them are used as ornamental plants of the Marene family (Rubiaceae). These epiphytic plants growing in Australasia provide ants with a place to build nests, forming special hollow structures - dominations on the stem, and insects supply plants with nutrients from their excrement and brought "garbage". This mutualism can be either specialized, in which one species of a plant is inhabited by one specific species of ants (the entrance to the dominions turns out to be precisely adjusted to the size of an individual of this species), or non-specialized (generalized), when one species of plants can be populated by different species of ants. In the aforementioned group of plants there are both of these variants and, in addition, some species do not enter into relationships with ants at all (Fig. 1). And the total number of species (105) provides sufficient material to verify 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 (for example, the rarity of ants or the availability of nutrients)?

3) Does the loss of mutualism affect the rate of evolution of the entrance to the domination (as long as the plant interacts with the ants, stabilizing selection, reducing variability, should act on this trait, 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 105 species of subtribe, and using two statistical methods (maximum likelihood estimates, see Maximum likelihood and Bayesian analysis, see Bayesian inference) revealed that, in contrast to their expectations, the initial state for this group of plants was unspecialized symbiosis, subsequently lost about 12 times (this tree is only an approximate reconstruction of a real evolutionary history, therefore, the obtained value may be inaccurate). 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 hydophytes - and this model built a tree much worse.

Eleven of the twelve cases of the disappearance of symbiosis occurred in non-specialized lines. The only exception is the genus Anthorrhiza, in which the ancestral state could not be established with certainty.

17 out of 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 with the rise in the mountains the diversity and abundance of ants decreases - this trend is also observed on this island. Moreover, in three of these species, rainwater accumulates in the dominions and frogs live (Fig. 1, D), six species can receive nutrients from the soil, but this is also true for two species that maintain a specialized connection with ants. All these facts speak in favor of the hypothesis that the cause of the loss of mutualism is not the loss of need for it, but the lack of potential partners. Here is the explanation and the absence of cases of loss of connection with ants in specialized species: having lost a partner, they simply die out.

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

What happens to dominations 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 affected by stabilizing selection that maintains the optimal size. Moreover, this selection should be stronger among specialists, that is, the rate of evolution should be minimal. And after the plant has ceased to interact with ants, the selection should weaken, which will lead to an increase in the rate of change of this trait.

The size of the inlet hole in the domination varies significantly among hydrophytes: from a millimeter to more than 5 centimeters. Analysis of the distribution of these sizes between species showed that many non-dualistic species have large openings - large invertebrates (cockroaches, centipedes, peripatuses, spiders, slugs and leeches) and even small vertebrates (frogs, geckos, and skinks) can penetrate into the dominance through them. The resulting estimate of the rate of evolution of the diameter of the hole is also consistent with the hypothesis: among specialists - 0.01 ± 0.04, among generalists - 0.04 ± 0.02, among nonmutualists - 0.1 ± 0.02 (values \u200b\u200bin arbitrary units, cm DL Rabosky, 2014. Automatic Detection of Key Innovations, Rate Shifts, and Diversity-Dependence on Phylogenetic Trees).

However, the high rate of evolution of the inlet size of the domination can be explained by the fact that, in the absence of communication with ants, selection arises that favors the penetration of larger animals. However, evidence is still unknown that these tenants benefit the plant, although this possibility requires further study.

Finally, the authors showed that as they move into the mountains, the average speed of the morphological evolution of the Domoician holes increases — for this they developed a method that combines data on the phylogeny and distribution of species, which allowed them to obtain a “map of morphological evolution” (Fig. 4).

This study did not reveal something completely unexpected, but it does not become less valuable. After all, theoretical predictions should be tested on "living" material. The authors were lucky to find a successful object for research. Let's hope that other similar works will follow, which will make it possible to understand how often these or other scenarios of the evolution of mutualism are realized.

A source: G. Chomicki, S. S. Renner. Partner abundance controls 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

Botanists from the University of Munich studied the evolution of the symbiosis between ants and myrmecophilous plants from the group of Gidnofitovye, forming special tissue growths - domination, in which these insects settle, providing nutrients in return to the owners. This mutually beneficial cooperation, as it turned out, is the starting point for this group of plants, but was lost several times during evolution. The results of the study confirmed several existing theoretical predictions. Firstly, a return to non-symbiotic life occurs only in non-specialized plants that have not developed a strict relationship with a specific species of ants. Secondly, the loss of symbiosis occurs in conditions of a low abundance of ant partners, and not due to the loss of need for it. Thirdly, after losing contact with ants, the morphological evolution of domocians, freed from the effect of stabilizing selection, which preserves them in symbiotic species, accelerates.

Mutually beneficial cooperation - mutualism - is now often considered by experts on co-evolution as one of the main mechanisms of complicating and maintaining the sustainability of ecosystems. It is appropriate to recall the symbiosis of 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. Not so close (it is now called symbiotic), as in the above examples, the mutualism of plants and pollinators, as well as plants and animals propagating seeds, is also very important for the functioning of ecosystems. In the end, the mitochondria and chloroplasts necessary for the development of complex multicellular organisms are the descendants of bacteria that have finally lost the ability to live freely and become organelles.

However, the high rate of evolution of the inlet size of the domination can be explained by the fact that, in the absence of communication with ants, selection arises that favors the penetration of larger animals. However, evidence is still unknown that these tenants benefit the plant, although this possibility requires further study.

Finally, the authors showed that as they move into the mountains, the average speed of the morphological evolution of the Domoician holes increases — for this they developed a method that combines data on the phylogeny and distribution of species, which allowed them to obtain a “map of morphological evolution” (Fig. 4).

This study did not reveal something completely unexpected, but it does not become less valuable. After all, theoretical predictions should be tested on "living" material. The authors were lucky to find a successful object for research. Let's hope that other similar works will follow, which will make it possible to understand how often these or other scenarios of the evolution of mutualism are realized.

Task 1. Write down the required characteristic numbers.

Signs:

1. Consist of complex organic and inorganic substances.

2. Absorb solar energy and form organic matter.

3. Eat ready-made organic substances.

4. Most representatives reproduce only sexually.

5. The body is metabolized and energy.

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

7. The vast majority of representatives are actively moving.

8. Grow throughout life.

9. Constantly adapt to environmental conditions.

Signs of all organisms: 5, 9.

Signs of plants: 2, 6, 8.

Signs of animals: 3, 4, 7.

Task 2. Fill in the table.

Task 3. Mark the correct answer.

1. Symbiosis exists:

a) between ant and aphids.

2. Housing exists:

b) between the sticky fish and the body of the shark.

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

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

4. The largest number of species is:

a) in the class of insects.

5. Animals are different from plants:

c) the way of nutrition.

6. Of the listed animals in two environments inhabits:

b) field mouse;

c) ladybug.

7. Destroyers of organic substances are:

b) mold fungi.

8. The most effective way to save the animal world 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 matter from inorganic and produce oxygen.

10. White hare and brown hare belong to different species, because they:

b) have significant differences in appearance.

11. Related animal births combine:

b) in the family.

12. For all living organisms are characteristic signs:

b) breathing, nutrition, growth, reproduction.

13. The sign on which the statement of kinship between animals and plants is based:

b) feed, breathe, grow, multiply, have a cellular structure.

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

Task 4. Fill in the gaps in the text.

Between organisms in the biological community are established food and trophic  communication. autotrophic organisms are again the food chain. They use solar energy to form organic matter from carbon dioxide  and water. Herbivores feed on producers, which, in turn, are eaten by carnivores. Animals are called organisms - heterotrophs. Destructive organisms (bacteria, gryuy, 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 numbers of the names of organisms from the list.

Names of organisms:

1. Earthworm.

2. The hare.

5. Wheat.

6. White clover.

7. Dove.

8. Bacteria.

9. Chlamydomonas.

Organic matter producers: 5, 6, 9.

Organic Consumers: 2, 4, 7, 10.

Destroyers of organic substances: 1, 3, 8.

Wonderful symbiosis

The nature around us sometimes demonstrates such unusual forms of cooperation between animals and plants that even biologists shrug their hands in surprise. One of the most amazing manifestations of symbiosis is the relationship between different types of tropical ants and the plants on which they live. Unfortunately, in 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 can belong to different systematic groups, but on an ecological basis they are often united under the general name of "ant trees." These plants literally provide their residents with a table and a house. And ants, in turn, not only collect various insect pests from them, but also protect them from herbivorous mammals more reliably 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 flood level often rises several meters, so the ants simply cannot live on the earth and they have to create shelters on the "upper floors" of the rainforest. While there is no flood, the ants diligently drag pieces of soil onto the trunks, which they stick together with special secretions, creating a solid base for the nest. Together with the soil, the ants bring up the seeds of various plants, including bromeliads, which find favorable conditions for themselves in the suspension nest being built and sprout quickly. Interestingly, their roots do not destroy them, but, on the contrary, fasten the nest. Moreover, the bromeliad roots 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 the bromeliads - other tropical epiphytes, which are often called "ant epiphytes," can develop in this way. The structures resulting from their growth are beautifully called "hanging ant gardens."

Ant Garden in the Amazon Rainforest

The second version of the symbiosis between plants and ants can also be found on the shores of the Amazon - where there are numerous trees from the family Melastomataceae. On the upper surface of the leaves of many species of these trees, on their leaf petioles or on the stem under the petiole, large swellings can be seen - double bubbles separated by a longitudinal septum, opening outwards with small holes. In these hollow swellings, called formicariae (from the Latin word Formica - an ant), small but very painfully biting ants settle, which, in gratitude for the house provided, protect the plant from various pests, and most importantly, from leaf-cutting ants capable of their " agricultural "needs for a short time to completely deprive the leaves of a large tree. Local residents also avoid touching plants that carry "ant bags", as you just shake them slightly, as perturbed insects get out of their shelters and attack troublemakers.

"Ant bags" on the leaves are found not only in representatives of the family of melastomas, but also in plants from other groups. For example, excellent cottages from leaves are built by some creepers from the family Gore (Aslepiadaceae). In some of them, rounded leaves, arranged in two rows along the stem, bend and snuggle tightly against the bark of the host tree. In the axils of such leaves, roots develop that not only firmly hold the leaf in place, but also absorb moisture and nutrients, giving life to the whole vine. Under such leaves-pockets, excellent conditions are created for the life of ants, who gladly settle there.

Another funniest shelter house is given to ants by another liana family, Raffleza dischidia (Dischidia rafflesiana), which grows in Southeast Asia. This vine usually carries two types of leaves: fleshy rounded and mutated into peculiar bags or pitchers, formed by wrapped sheets on the underside and fused along the edge. The base of such a sheet turned upwards has a rather wide hole bordered by a roller, into which a highly branched air root enters. This root absorbs water falling into the jug, and also serves as an excellent ladder for ants, who often settle in these fun natural tents.