Fundamentals of population ecology. Fedoruk A.T. Short course of lectures on ecology Age structure of plant populations

INTRODUCTION

Russian hazel grouse ( Fritillaria ruthenica Wikstr.) is a species from the Liliaceae family. F.ruthenica listed in the Red Book of Russia, in the regional Red Books of Saratov, Volgograd, Samara, Penza, Lipetsk, Tambov, Bryansk regions. Study of age states of coenopopulations F. ruthenica in the Balashovsky district, as a rare and protected species of plant is relevant, which determines the purpose of this study.

This is a perennial bulbous herbaceous plant with drooping flowers (life expectancy up to 20 years). The perianth is simple, corolla-shaped, six-membered. The fruit is a capsule. This is a Eurasian species. Leaf growth begins in the second ten days of April and continues until the second ten days of May. Growing season duration F. ruthenica at different age periods from 30 to 80 days. Depending on the timing and time of soil thawing, fluctuations between the dates of the beginning of the growing season in some years can reach 20-22 days. During the summer dormancy period, only the bulb is preserved. F. ruthenica reproduces both by seeds and vegetatively (by renewal buds from bulbs or adventitious brood buds). F. ruthenica- xeromesophyte. Demanding on soils.

Category and status F. ruthenica V Saratov region 2 (V) - vulnerable species. It grows in steppe meadows, among shrubs, on the edges and clearings of deciduous forests, in steppe oak forests, and on rocky chalk slopes. The limiting factors are collection by the population and violation of the integrity of habitats.

MATERIALS AND METHODS OF RESEARCH

To study the state of coenopopulations F. ruthenica Test plots measuring 1x1 m were laid out. At each trial plot, the total number of individuals per 1 m 2 was taken into account. U F. ruthenica The following biometric indicators were measured: height, number of lower, middle and upper leaves, number of flowers, length of tepals. When analyzing these indicators, the age states of individuals were determined and ontogenetic spectra were compiled. When determining the age structure of the population, individuals of seed and vegetative origin were taken as the accounting unit. Age conditions were determined according to the Works of M.G. Vakhromeeva, S.V. Nikitina, L.V. Denisova, I. Yu. Parnikoza. Recovery, age and efficiency indices were determined according to the method of A.A. Uranova. The recovery index shows how many descendants there are per generative individual in this moment. The age index evaluates the ontogenetic level of CP at a specific point in time; it varies in the range of 0-1. The higher its indicator, the older the CPU under study. The efficiency index, or average energy efficiency, is the energy load on the environment, called the "average" plant. It also varies from 0 to 1, and the higher it is, the older the age group of the “average” plant.

With age, an individual's requirements for the environment and resistance to its individual factors naturally and very significantly change. At different stages of ontogenesis, changes in habitats, changes in the type of food, the nature of movement, and the general activity of organisms can occur. Often, age-related ecological differences within a species are expressed to a much greater extent than differences between species. Grass frogs on land and their tadpoles in ponds, caterpillars gnawing leaves and winged butterflies sucking nectar, sessile sea lilies and their planktonic doliolaria larvae are just different ontogenetic stages of the same species. Age-related differences in lifestyle often lead to the fact that certain functions are performed entirely at a certain stage of development. For example, many species of insects with complete metamorphosis do not feed in the adult state. Growth and nutrition are carried out during the larval stages, while adults perform only the functions of dispersal and reproduction.

Age differences in a population significantly increase its ecological heterogeneity and, consequently, its resistance to the environment. The likelihood increases that, in the event of strong deviations of conditions from the norm, at least some viable individuals will remain in the population and it will be able to continue its existence. The age structure of populations is adaptive in nature. It is formed on the basis of the biological properties of the species, but always also reflects the strength of the influence of environmental factors.

Age structure of plant populations. In plants, the age structure of the cenopopulation, i.e., the population of a particular phytocenosis, is determined by the ratio of age groups. The absolute, or calendar, age of a plant and its age state are not identical concepts. Plants of the same calendar age can be in different age states. Age, or ontogenetic state of the individual - this is the stage of its ontogenesis, at which it is characterized by certain relationships with the environment. Complete ontogenesis, or the large life cycle of plants, includes all stages of the development of an individual - from the emergence of the embryo to its death or to the complete death of all generations of its vegetatively arising offspring (Fig. 97).

Rice. 97. Age conditions of meadow fescue (A), Siberian cornflower (B):

R- sprouts; j- juvenile plants; im- immature; v- virginal; g 1- young generative; g 2- middle-aged generative; g 3- old generative; ss - subsenile; s - senile

Sprouts have a mixed diet due to the reserve substances of the seed and their own assimilation. These are small plants, which are characterized by the presence of embryonic structures: cotyledons, an embryonic root that has begun to grow, and, as a rule, a uniaxial shoot with small leaves that often have more simple form than in adult plants.

Juvenile plants begin to feed themselves. They lack cotyledons, but the organization is still simple, they often remain uniaxial and the leaves are of a different shape and smaller in size than those of adults.

Immature plants have characteristics and properties that are transitional from juvenile plants to adult vegetative ones. Their shoots often begin to branch, which leads to an increase in the photosynthetic apparatus.

U adult vegetative In plants, features of a life form typical of the species appear in the structure of underground and above-ground organs, and the structure of the vegetative body fundamentally corresponds to the generative state, but reproductive organs are still absent.

The transition of plants into the generative period is determined not only by the appearance of flowers and fruits, but also by a deep internal biochemical and physiological restructuring of the body. In the generative period, Colchicum splendid plants contain approximately twice as much colchamine and half as much colchicine as in young and old vegetative individuals; in the eastern sverbiga, the content of all forms of phosphorus compounds sharply increases, as well as the activity of catalase, the intensity of photosynthesis and transpiration; in the reznikovaya gill, the RNA content increases 2 times, and total nitrogen increases 5 times.

Young generative plants bloom, form fruits, and the final formation of adult structures occurs. In some years there may be breaks in flowering.

Middle-aged generative plants usually reach their greatest vigor, have the greatest annual growth and seed production, and may also have a break in flowering. In this age state, clone-forming species often begin to exhibit disintegration of individuals and clones arise.

Old generative plants are characterized by a sharp decrease in reproductive function, weakening of the processes of shoot and root formation. The processes of death begin to prevail over the processes of new formation, and disintegration intensifies.

Old vegetative (subsenile) plants are characterized by the cessation of fruiting, a decrease in power, an increase in destructive processes, a weakening of the connection between the shoot and root systems, a simplification of the life form is possible, and the appearance of immature-type leaves.

Senile plants are characterized by extreme decrepitude, reduction in size, upon renewal, few buds are realized, and some juvenile features appear a second time (shape of leaves, character of shoots, etc.).

Dying individuals - an extreme degree of expression of the senile state, when only some tissues of the plant remain alive and, in some cases, dormant buds that cannot develop above-ground shoots.

In some trees (pedunculate oak, forest beech, field maple, etc.) quasi-senile age-related condition (the term was proposed by T. A. Rabotnov). These are depressed, low-growing plants, described as upright plants (Fig. 98). Over time, they acquire the features of an old vegetative plant without ever going through the generative phase.

Rice. 98. Ontogenesis of pedunculate oak under favorable conditions (above) and with a lack of light (according to O. V. Smirnova, 1998)

The distribution of individuals of a cenopopulation according to age states is called its age, or ontogenetic spectrum. It reflects the quantitative relationships of different age levels.

To determine the size of each age group, different types use different counting units. Individual individuals can be a counting unit if during the entire ontogeny they remain spatially isolated (in annuals, taproot mono- and polycarpic herbs, many trees and shrubs) or are clearly demarcated parts of the clone. In long-rhizome and root-sprouting plants, the counting unit can be partial shoots or partial bushes, since with the physical integrity of the underground sphere they often turn out to be physiologically separated, which was established, for example, for lily of the valley when using radioactive phosphorus isotopes. In dense-turf grasses (pike, fescue, feather grass, snake grass, etc.), the counting unit, along with young individuals, can be a compact clone, which in relations with the environment acts as a single whole.

The number of seeds in the soil reserve, although this indicator is very important, is usually not taken into account when constructing the age spectrum of a coenopopulation, since counting them is very labor-intensive and it is almost impossible to obtain statistically reliable values.

If the age spectrum of a cenopopulation at the time of its observation contains only seeds or young individuals, it is called invasive. Such a coenopopulation is not capable of self-sustaining, and its existence depends on the supply of rudiments from the outside. Often this is a young coenopopulation that has just entered the biocenosis. If a coenopopulation is represented by all or almost all age groups (some age conditions in specific species may not be expressed, for example, immature, subsenile, juvenile), then it is called normal. Such a population is independent and capable of self-sustaining by seed or vegetative means. It may be dominated by certain age groups. In this regard, young, middle-aged and old normal coenopopulations are distinguished.

A normal coenopopulation consisting of individuals of all age groups is called full-membered, and if individuals of any age conditions are absent (in unfavorable years, certain age groups may temporarily drop out), then the population is called normal incomplete.

Regressive the coenopopulation is represented only by senile and subsenile or also generative, but old, not forming viable seeds. Such a coenopopulation is not capable of self-sustaining and depends on the introduction of rudiments from the outside.

An invasive coenopopulation can turn into a normal one, and a normal one into a regressive one.

The age structure of the coenopopulation is largely determined by the biological characteristics of the species: the frequency of fruiting, the number of produced seeds and vegetative rudiments, the ability of vegetative rudiments to rejuvenate, the rate of transition of individuals from one age state to another, the ability to form clones, etc. The typical age spectrum is called basic(Fig. 99). The manifestation of all these biological features, in turn, depends on environmental conditions. The course of ontogenesis also changes, which can occur in one species in many variants (polyvariance of ontogenesis), which affects the structure of the age spectrum of the cenopopulation (Fig. 100).

Rice. 99. Basic type of coenopopulation spectrum (according to L.B. Zaugolyyuva, 1976) A - Lena alyssum; B - leafless anabasis; B - meadow fescue; G - fescue.

1 - basic spectrum; 2 - limits of change in the base spectrum

Different plant sizes reflect different vitality individuals within each age group. The vitality of an individual is manifested in the power of its vegetative and generative organs, which corresponds to the amount of accumulated energy, and in resistance to adverse influences, which is determined by the ability to regenerate. The vitality of each individual changes in ontogenesis along a single-peak curve, increasing on the ascending branch of ontogenesis and decreasing on the descending branch. In many species, individuals of the same age state in the same coenopopulation may have different vitality. This differentiation of individuals in terms of vitality can be caused by different quality of seeds, different periods of their germination, microenvironmental conditions, the influence of animals and humans, and competitive relations. High vitality can remain until the death of an individual in all age states or decrease during ontogenesis. Plants high level vitality often passes through all age-related conditions at an accelerated pace. Cenopopulations are often dominated by plants with an average level of vitality. Some of them go through ontogenesis completely, while others skip some of the age-related states, passing to a lower level of vitality before dying. Plants lower level vitality has a shortened ontogeny and often passes into a senile state as soon as it begins to flower.

Rice. 100. Options for the development of hedgehogs in different environmental conditions (according to L. A. Zhukova, 1985). Latin letters indicate the age states of plants, and dotted lines indicate their possible sequence

Individuals of the same coenopopulation can develop and move from one age state to another at different rates. Compared to normal development, when age-related states replace each other in the usual sequence, there may be an acceleration or delay in development, the loss of individual age-related states or entire periods, the onset of secondary dormancy, and some individuals may rejuvenate or die. Many meadow, forest, and steppe species, when grown in nurseries or crops, i.e., on the best agrotechnical background, shorten their ontogeny, for example, meadow fescue and hedgehog grass - from 20-25 to 4 years, spring adonis - from 100 to 10 -15 years, gilly frog - from 10-18 to 2 years. In other plants, when conditions improve, ontogenesis can lengthen, such as in caraway seeds.

In dry years and with increased grazing, the steppe species Schell's sheep loses certain age-related conditions. For example, adult vegetative individuals can immediately replenish the group of subsenile, or less often, old generative ones. Tuberous-bulbous plants of Colchicum splendidum in the central parts of compact clones, where conditions are less favorable (poor lighting, moisture, mineral nutrition, toxic effects of dead residues), quickly pass into a senile state than peripheral individuals. In the eastern sverbiga, under increased pasture load, when renewal buds are damaged, young and mature generative individuals may have breaks in flowering, thereby seeming to rejuvenate and prolong their ontogenesis.

In the common hedgehog, in different conditions, from 1-2 to 35 paths of ontogenesis are realized, and in the great plantain, from 2-4 to 100. The ability to change the path of ontogenesis ensures adaptation to changing environmental conditions and expands the ecological niche of the species.

In two species of steppe sheep - Shell and pubescent - in Penza region The cyclical change in age spectra in long-term dynamics is clearly traced. In dry years, sheep populations become older, and in wet years, they become younger. Fluctuations in the age spectrum of cenopopulations following weather conditions are especially characteristic of plants in floodplain meadows.

The age spectrum can vary not only due to external conditions, but also depending on the reactivity and stability of the species themselves. Plants have different resistance to grazing: in some, grazing causes rejuvenation, since the plants die off before reaching old age (for example, in lowland wormwood), in others it contributes to the aging of the coenopopulation due to a decrease in regeneration (for example, in the steppe species of Ledebur's gill).

In some species, throughout the entire range in a wide range of conditions, normal coenopopulations retain the main features of the age structure (common ash, fescue, meadow fescue, etc.). This age spectrum depends primarily on the biological properties of the species. It primarily preserves the relationships in the adult, most stable part. The number of newly emerging and dying individuals in each age group is balanced, and the overall spectrum turns out to be constant until significant changes in living conditions. Such basic spectra most often have coenopopulations of edificator species in stable communities. They are contrasted with coenopopulations that relatively quickly change their age spectrum due to unestablished relationships with the environment.

The larger the individual, the more significant the sphere and the degree of its influence on the environment and on neighboring plants (“phytogenic field”, according to A. A. Uranov). If the age spectrum of the cenopopulation is dominated by adult vegetative, young and middle-aged generative individuals, then the entire population as a whole will occupy a stronger position among others.

Thus, not only the number, but also the age spectrum of the cenopopulation reflects its state and adaptability to changing environmental conditions and determines the position of the species in the biocenosis.

Age structure of populations in animals. Depending on the characteristics of reproduction, members of a population may belong to the same generation or to different ones. In the first case, all individuals are close in age and approximately simultaneously go through the next stages of the life cycle. An example is the reproduction of many species of non-gregarious locusts. In the spring, first instar larvae emerge from eggs that have overwintered in egg capsules laid in the ground. The hatching of larvae is somewhat prolonged under the influence of microclimatic and other conditions, but on the whole it proceeds quite smoothly. At this time, the population consists only of young insects. After 2-3 weeks, due to the uneven development of individual individuals, larvae of adjacent ages may simultaneously be found in it, but gradually the entire population passes into the imaginal state and by the end of summer consists only of adult sexually mature forms. By winter, having laid eggs, they die. The age structure of populations of the oak budworm, slugs of the genus Deroceras, and other species with an annual development cycle that reproduce once in a lifetime is the same. The timing of reproduction and the passage of individual age stages is usually confined to a certain season of the year. The size of such populations is, as a rule, unstable: strong deviations of conditions from the optimum at any stage of the life cycle immediately affect the entire population, causing significant mortality.

Species with the simultaneous existence of different generations can be divided into two groups: those that reproduce once in a lifetime and those that reproduce many times.

In May beetles, for example, females die soon after laying eggs in the spring. The larvae develop in the soil and pupate in the fourth year of life. At the same time, there are representatives of four generations in the population, each of which appears a year after the previous one. Every year one generation completes its life cycle and a new one appears. Age groups in such a population are separated by a clear interval. Their ratio in numbers depends on how favorable the conditions turned out to be during the emergence and development of the next generation. For example, the generation may be small if late frosts destroy some of the eggs or cold rainy weather interferes with the flight and copulation of beetles.

Rice. 101. The ratio of age groups of herring over 14 years. “Prolific” generations can be traced over several years (according to F. Schwerdpfeger, 1963)

In species with single reproduction and short life cycles, several generations occur throughout the year. The simultaneous existence of different generations is due to the protracted nature of oviposition, growth and sexual maturation of individual individuals. This occurs both as a result of the hereditary heterogeneity of members of the population, and under the influence of microclimatic and other conditions. For example, the beet moth, which harms sugar beets in the southern regions of the USSR, has caterpillars of different ages and pupae overwintering. Over the summer, 4-5 generations develop. Representatives of two or even three adjacent generations meet at the same time, but one of them, the next in time, always prevails.

Rice. 102. Age structure of populations in animals (according to Yu. Odum, 1975; V.F. Osadchikh and E.A. Yablonskaya, 1968):

A - general diagram, B - laboratory populations of the vole Microtus agrestis, C - seasonal changes in the ratio of age groups of the mollusk Adaena vitrea in the Northern Caspian Sea.

Different shading - different age groups:

1 - growing, 2 - stable, 3 - declining populations

The age structure of populations in species with repeated reproduction is even more complex (Fig. 101, 102). In this case, two extreme situations are possible: 1) life expectancy in adulthood is short and 2) adults live long and reproduce many times. In the first case, a significant part of the population is replaced annually. Its numbers are unstable and can change sharply in individual years, favorable or unfavorable for the next generation. The age structure of the population varies greatly.

In the housekeeper vole, the age structure of the population gradually becomes more complex over the summer season. At first, the population consists only of individuals of the previous year of birth, then young of the first and second litters are added. By the time the third and fourth offspring appear, sexual maturity occurs in representatives of the first two, and generations of the grandchild generation join the population. In autumn, the population consists mainly of individuals of different ages of the current year of birth, since the older ones die.

In the second case, a relatively stable population structure arises, with long-term coexistence of different generations. Thus, Indian elephants reach sexual maturity by 8-12 years and live up to 60-70 years. The female gives birth to one, or less often two, elephant calves approximately once every four years. In a herd, usually adult animals of different ages make up about 80%, young animals - about 20%. In species with higher fertility, the ratio of age groups may be different, but the overall structure of the population always remains quite complex, including representatives of different generations and their offspring of different ages. Fluctuations in the number of such species occur within small limits.

The long-term breeding part of the population is often called in stock. The possibilities of population restoration depend on the size of the population stock. That part of the young that reach sexual maturity and increase the stock is an annual replenishment populations. In species with the simultaneous existence of only one generation, the reserve is practically zero and reproduction is carried out entirely through replenishment. Species with a complex age structure are characterized by a significant stock size and a small but stable share of recruitment.

During human exploitation of natural animal populations, taking into account their age structure has vital importance(Fig. 103). In species with large annual recruitment, larger portions of the population can be removed without the threat of depleting its numbers. If you destroy many adults in a population with a complex age structure, this will greatly slow down its recovery. For example, in pink salmon that mature in the second year of life, it is possible to catch up to 50-60% of spawning individuals without the threat of a further decline in population size. For chum salmon, which mature later and have a more complex age structure, removal rates from a mature stock should be lower.

Rice. 103. Age structure of the Taimyr population of wild reindeer during the period of moderate (A) and excessive (B) hunting (according to A. A. Kolpashchikov, 2000)

Analysis of the age structure helps to predict the population size over the life of a number of next generations. Such analyzes are widely used, for example, in fisheries to predict the dynamics of commercial stocks. They use quite complex mathematical models with a quantitative expression of the impact on individual age groups of all environmental factors that can be taken into account. If the selected indicators of the age structure completely correctly reflect the real influence of the environment on the natural population, highly reliable forecasts are obtained that make it possible to plan the catch for a number of years in advance.

Basic concepts and terms : latent, pregenerative, generative and postgenerative periods of ontogenesis; age states of plants: seedlings, juvenile, mature, young vegetative, adult vegetative, young generative, middle-aged generative, subsenile and senile individuals; age spectrum; invasive and regressive coenopopulation.

When characterizing the age structure of populations in plants, one must keep in mind that the absolute age of a plant and its age state are different concepts.

Age state of a plant individual - this is a stage individual development plants on which it has certain environmental and physiological properties.

A large life cycle includes the stages of plant development from the formation of the seed embryo to death or the death of all its generations that arose from it vegetatively. In a large life cycle, ontogenetic periods and age states are distinguished (Table 5.1, Fig. 5.14).

Table 5.1.

Periods and age states in the life cycle of plants

Periods	Age conditions	Conditional designations
I. Latent	Seeds	Sm
II. Before generation	Sprouts (ladder)
(virgin)	Juveniles
	imaturni individuals	I m
	Young vegetative individuals
	Adult vegetative individuals
III. Generative	Young generative individuals
	Medieval generative individuals
	Old generative individuals
	Subsenile individuals
Postgenerative	Senile individuals
(senile)

Rice.5.14. Age states of plant ontogenesis : A - meadow fescue (grass family), B -

Siberian cornflowers (Asteraceae family).

p- sprouts; j- juvenile plants;i m - imaturni;v- virgin;g 1 - young generative;g 2 - middle-aged generative;g 3 - old generative;ss - subsenile;s - senile plants.

In plants, there are four periods of individual ontogenesis:

1) latent- the period of primary dormancy, when the plant is in the form of seeds or fruits;

2) virginal or pregenerative - from seed germination to the formation of generative organs;

3) generative- period of plant propagation by seeds or spores;

4)senile or postgenerative - this is a period of sharp decline and loss of the ability to sexually reproduce, which ends with the complete death of plants.

Each period is characterized by corresponding age-related conditions. The duration of individual periods of individual development, the nature and time of transition from one age state to another is a biological feature of the plant species and its adaptation to environmental conditions in the process of evolution.

Seedscharacterized by relative rest, when metabolism in it is reduced to a minimum. Ladders have rudimentary roots and cotyledon leaves; they also feed on the reserve nutrients of the seeds and photosynthesis of the cotyledons.

Juvenileplants switch to self-feeding. Mostly they lack cotyledons, but the leaves are still atypical, smaller in size and of a different shape than those of adults.

imaturni plants show signs of transition from juvenile to adult. Their shoots begin to branch and typical leaves appear. Juvenile characteristics are gradually replaced by those typical for the plant species. This condition is long-term in some species.

Vegetativeindividuals (virginile) are characterized by the process of formation of a typical life form of plants with the corresponding typical characteristics of the morphological structure of underground organs and above-ground pagon system. Plants are finishing pregenerative period of its life cycle. Generative organs are still missing. At different stages of the formation of a typical vegetative sphere, young and adult vegetative individuals are distinguished, ready to enter the generative phase of development.

Generative individuals characterized by the transition to flowering and fruiting. Young generative individuals complete the formation of the typical structures of the species. Generative organs (flowers and inflorescences) appear in them, and their first flowering is observed.

Middle-aged generative individuals are marked by an annual maximum increase in the vegetative sphere due to the development of new enrichment shoots, abundant flowering and high seed productivity. Plants can remain in this state for different periods of time, depending on the life expectancy and biological characteristics of the species ontogenesis. This is one of the most important periods in the life of a plant, which attracts the attention of theoreticians and practitioners. The regulatory influence on cultivated forage and ornamental garden plants makes it possible to prolong their youth and increase the productivity of the former and the decorative qualities of others.

Old generative and individuals weaken the process shoot formation, sharply reduce seed productivity. The processes of death begin in them, which gradually prevail over the processes of formation of new pagon structures.

Senile individuals are distinguished by a clearly defined aging process. Small shoots with juvenile-type leaves appear. The plant dies over time.

The age distribution of individuals in a plant cenopopulation is called age spectrum. If the age spectrum of plants is represented by seeds and young individuals, such a cenopopulation is called Invasive.

More often than not, there is a young population that has just been introduced into the phytocenosis of a certain biogeocenosis.

There are normal and complete normal inferior cenopopulations.

Normal full-fledged coenopopulation represented by all age conditions and is capable of self-care by seeds or vegetative propagation.

Inferior normal coenopopulation called one in which there are no individuals of certain age conditions (ladder or, most often, senile individuals). These are plant populations

Monocarpics that bear fruit once in a lifetime. These are annual and biennial plants.

A detailed classification of plant populations was developed by T.A. Rabotnov (1946). Among plant populations within the phytocenosis, he distinguishes several types:

I. Invasive populations. Plants are just taking root in phytosenosis and do not complete the full development cycle.

This type has subtypes:

1) plants are found only in the form of a ladder, arising from introduced seeds from other populations;

2) plants are found in the form of seedlings, juveniles and vegetative individuals. For various reasons, they do not bear fruit and reproduce only by introducing seeds.

II. Normal type populations. Plants go through a full development cycle in a phytocenosis.

It has subtypes:

1) the plants are in optimal conditions. The population has a high percentage of generative individuals;

2) plants of this species are in average conditions and, accordingly, the population contains significantly fewer generative individuals;

3) the plants are not in very favorable conditions; there are few generative individuals in the population.

III. Populations of regressive type. The generative reproduction of plants in it has ceased.

This population type includes subtypes:

1) the plant blooms, produces seeds, but non-viable shoots grow from it; or the plant does not produce seeds at all. Therefore, in such populations there is no young juveniles;

2) the plant has completely lost the ability to flower and is only vegetating. Consequently, the population consists of old individuals.

This classification of plant populations makes it possible to determine their development prospects in a given ecosystem based on an analysis of the action of environmental factors.

Cenopopulations, which include only old subsenile and senile individuals, are not capable of self-care, are called regressive. They can exist due to the introduction of seeds or rudiments from other coenopopulations.

The age structure of coenopopulations is determined by such properties of the species as: frequency of fruiting, rate of transition from one age state to another, duration of each state, duration of a large life cycle, ability for vegetative reproduction and formation of clones, resistance to diseases and adverse natural conditions, etc.

In the case when a cenopopulation is characterized by high seed productivity and mass emergence of seedlings with significant death of young individuals and the rapid transition of those that remain into a vegetative and generative state, its age spectrum has a left-handed character. This is the spectrum of young coenopopulations (Fig. 5.15).

Rice.5.15. Age spectra of coenopopulations:

A - left-sided spectrum of Colchicum lush;

B - right-hand spectrum of the Meadow fire;

1, 2 - variability over the years.

If seed productivity is low, there are few young individuals, and the accumulation of adult individuals occurs due to the significant duration of their age states and during the formation of a clone, the cenopopulation spectrum will have a right-handed character. It is a sign of her aging.

The age spectrum of the cenopopulation and its size determine the role of the species in the phytocenosis.

III. Generative	Generative young (early)
	Generative middle-aged (adult)

	Generative old (late)

IV. Postgenerative	Subsenile (old vegetative)
ny (senile, gray)	Senile
	Dying

above the soil surface level; when underground, for example, near an oak tree, they remain in the soil. The first leaves, for example those of spruce, are thin, short (up to 1 cm long), round in cross-section and often located.

3. Juvenile plants. Plants that have lost connection with the seed

A also cotyledons, but have not yet acquired the features and characteristics of an adult plant. They are easy to organize. They have childish (infantile) structures. Their leaves are small in size, not typical in shape (in spruce they are similar to the needles of seedlings), and there is no branching. If branching is pronounced, then it is qualitatively different from the branching of immature individuals. They are characterized by high shade tolerance, being part of the herbal but-shrub layer.

4. Immature plants. They are characterized by transitional characteristics and properties from juvenile to adult vegetative individuals. They are larger, develop leaves in shape more similar to the leaves of adult plants, and have pronounced branching. The nutrition is autotrophic. At this stage, the main root dies off, adventitious roots and tillering shoots develop. Immature trees are part of the understory layer. In low light conditions, individuals are delayed in development and then die off. In young children, this stage is usually not recorded. In spruce it is usually observed in the fourth year of life.

The identification of immature plants is most difficult and some authors combine them into one group with virginile plants.

5. Virgin plants. They have morphological features typical for the species, but do not yet develop generative organs. This is the phase of preparing the morphophysiological basis for achieving physiological maturity, which will come at the next stage. Virgin trees have almost fully formed features of an adult tree. They have a well-developed trunk and crown, and maximum height growth. They are part of the tree canopy and experience the maximum need for light.

6. Generative young plants. Characterized by the appearance of the first generative organs. Flowering and fruiting are not abundant, the quality of the seeds may still be low. Complex changes occur in the body to ensure the generative process. The processes of neoplasms prevail over death. The growth of trees in height is intensive.

7. Generative middle-aged plants. In this age state, individuals reach their maximum size, are distinguished by large annual growth, abundant fruiting, high quality seeds The processes of new growth and death are balanced. The apical growth of some large branches of trees stops, and dormant buds awaken on the trunks.

8. Generative old plants. Annual growth is weakened, the indicators of the generative sphere are sharply reduced, and the processes of death prevail over the processes of new formation. The trees are actively awakening dormant buds, and the formation of a secondary crown is possible. Seeds are produced irregularly and in small quantities.

9. Subsenile plants. They lose the ability to develop the generative sphere. Dying processes predominate; secondary appearance of transitional (immature) type leaves is possible.

10. Senile plants. They are characterized by features of general decrepitude, which is expressed in the death of parts of the crown, the absence of renewal buds and other neoplasms; possible secondary appearance of some juvenile features. Trees usually develop a secondary crown and the upper part of the crown and trunk dies.

11. Dying plants. Dead parts predominate; there are single viable dormant buds.

The listed age-related conditions are characteristic of polycarpics. Diagnoses and age-related condition keys have been developed for a range of herbaceous plants.

And tree species (Diagnosis and keys..., 1980, 1983, 1989; Romanovsky, 2001). In monocarpics, the generative period is represented by only one age state, and the postgenerative period is completely absent.

In animals, with varying degrees of accuracy, individuals are usually distinguished as “young”, “yearlings”, “yearlings”, “adults”, “old”. G.A. Novikov (1979) distinguishes five age groups of animals:

1. Newborns (until the time of sight).

2. Juveniles are growing individuals that have not yet reached sexual maturity.

3. Sub-adults – close to puberty.

4. Adults are sexually mature individuals.

5. Old are individuals that have stopped reproducing.

V.E. Sidorovich (1990) distinguished three age groups in otter populations: young individuals (first year of life), semi-adults (second year of life), adults (third year of life and older). In the Belovezhskaya bison population, adults make up 57.8%, young animals (from 1 year to 3.5 years) - 27.9, young of the year - 14.3% (Bunevich, 1994). Age-related differences are most clearly manifested in species whose development occurs with metamorphosis (egg, larva, pupa and adult).

Individuals of different age groups, both in plants and animals, inevitably developing in different conditions, differ markedly not only in morphological, but also in quantitative indicators. They have biological and physiological differences, play different roles (plants) in the formation of communities, in biocenotic relationships. Seeds in plant populations, for example, being dormant, express the potential capabilities of the population. Seedlings have mixed nutrition (endosperm nutrients and photosynthesis), juveniles and individuals of subsequent groups are autotrophs. Generative plants perform the function of self-sustaining population. The role of individuals in the life of the population, starting with subsenile plants, is weakening. Dying plants leave the population. During the process of ontogenesis, many species change their life form, as well as their attitude and degree of resistance to environmental factors.

The identification of age groups is always difficult, especially in animals, and is carried out using different methods. Most often, attention is paid to the time of transition to the generative state. The age of sexual maturity occurs at different times in different species. In addition, the timing of maturation of individuals in different populations of the same species is also different. In some populations of ermine (Mustela erminea), the phenomenon of neoteny is manifested - mating of still blind 10-day-old females (Galkovskaya, 2001). Beluga females mature at 15-16 years, males at 11 years. Under favorable conditions, beluga can enter rivers to spawn up to 9 times. During the river life period, females do not feed. Repeated maturation is observed after 4-8 years (females) and 4-7 years (males). The last spawning occurs at the age of about 50 years. The post-reproductive period lasts 6-8 years (Raspopov, 1993). Much earlier, at four or five years of age, females reach sexual maturity polar bear. Reproduction continues until the age of 20, repeats on average every 2 years, average litter size is 1.9 cubs

(Kuzmina, 2002).

The differences between age groups are also quite significant and species-specific in animals. In species with direct development, differences associated with reproduction, nutrition and functional development are clearly visible.

role. Young individuals determine the potential for future reproduction, while mature individuals carry out reproduction. In bank vole (Clethrionomys glareolus) populations, individuals of spring and summer cohorts quickly mature, marry early, and are fertile, contributing to an increase in population size and expansion of its range. However, their teeth wear out quickly, they age early and live mostly 2-3 months. A small number of individuals survive until the spring of next year. As a rule, animals of the latest generations hibernate. They have small body sizes, much less than the relative weight of most internal organs(liver, kidneys), reduced rate of tooth abrasion, i.e. there is a sharp slowdown in growth. In addition, they have a very low mortality rate in winter. In terms of physiological state, wintering voles correspond to approximately month-old individuals of the spring-summer generations. They give birth and soon die off. Their descendants - individuals of early spring cohorts, distinguished by early maturation and fertility, quickly replenish the population thinned out during the non-reproductive period, closing the annual cycle (Shilov, 1997).

Thanks to the biological characteristics of wintering individuals, energy costs are reduced to a minimum during the most difficult time for the population. They successfully “drag” the population through the winter (Olenev, 1981). A similar pattern was noted in other rodent species. In steppe pieds (Lagurus lagurus), born in May, average age reaching sexual maturity was 21.6 days, and for those born in October - 140.9 days (Shilov, 1997). According to S.S. Schwartz, the experience of unfavorable conditions occurs in a state of “canned youth.” It is the increase in life expectancy of rodents of later cohorts that occurs not due to survival in old age, but by prolonging the physiologically youthful period (Amstislavskaya, 1970).

The generative period in woody plants (we noted in 230 species) also occurs at different times. Most early dates(4-5 years) were noted in species of several genera (willow, rowan, plum, bird cherry, ash maple); the latest (40 years) is found in forest beech. A very long pregenerative period of ontogenesis is a feature of the reproductive strategy of woody plants. Shrub species are distinguished by a relatively early (3-4 years) transition from virginity (Fedoruk, 2004).

coniferous species occurs during the maximum growth of the tree in height (Nekrsova, Ryabinkov, 1978; Shkutko, 1991; Fedoruk, 2004); with intensive radial growth of the trunk (Valisevich, Petrova, 2004). The faster the upward growth curve goes, the earlier the woody plant enters the reproductive phase. Physiological and structural changes in plants are associated with the maximum linear increase in height. Rapid growth allows plants to achieve a certain morphological structure and linear dimensions in a short time. With the attenuation of the culmination of height growth due to the redistribution of plastic substances, stable flowering and fruiting begins. Herbaceous plants begin fruiting also at a certain threshold value of vegetative mass

sy (Smith and Joung, 1982).

According to M.G. Popov (1983), as the amount of meristem begins to decrease and “the body becomes overgrown with a shell, the armor of permanent tissues,” its ability to grow decreases, the process of generative development begins, and with further depletion of the meristem, aging occurs . The mechanism of this phenomenon is very complex and far from clear. It is assumed that quantitative changes in metabolism lead to the activation of inert genes, the synthesis of specific RNAs and qualitatively new reproductive proteins (Berne, Kune, Saks, 1985, cited in: Valisevich, Petrova, 2004). Yu.P. Altukhov (1998) showed on botanical and zoological species that the greater the proportion of “heterotic” genes that are included in the processes of growth and puberty, the greater the energy expenditure of the organism in the pregenerative period of ontogenesis and the earlier the onset of sexual maturity.

Table Age of seed production and culmination of growth

in height of coniferous plants

Plant	Beginning of the family	The beginning of the cultural	Maximum
	wearing, go-		ny growth
		growth in	in height, th-
		height, years
Siberian fir

Fir one color

White fir

Balsam fir

Fir Vicha
Menzies's Pseudo-tsuga

Norway spruce
Gray spruce

Prickly spruce
European larch

Kaempfer's larch

Polish larch
Siberian larch
Larch Sukacheva
Weymouth pine

Siberian cedar pine
Scots pine

Rumelian pine
Austrian black pine

Pine is hard
Banks Pine

Thuja occidentalis

As a rule, different age groups of animals have different nutritional spectrums. Tadpoles, for example, are aquatic phytophages, frogs are zoophages leading a terrestrial lifestyle. Individuals of each age cohort of the brown hare (Lepus europaeus) are oriented toward different food resources; Each litter of mouse-like rodents also has its own food supply.

Differences in age groups in animals characterized by development with metamorphosis are no less clearly expressed. Adults chafer(Melolontha hippocastani) feed on tree leaves, the larvae feed on humus and plant roots. Cohorts are confined to different layers soil and depending on its temperature and humidity, the availability of food, beetles fly out at different times, which provides the population with numerous adaptive strategies. The food of the cabbage butterfly (Pieris brassicae), the largest among local garden whites, is the nectar of cruciferous plants, while the caterpillars eat cabbage leaves. At the same time, young caterpillars, grayish-green, with black dots and a light yellow stripe on the dorsal side, scrape off the pulp of the leaf; grown individuals make small holes in the leaves; older caterpillars, colored green color, with bright black spots and three bright yellow stripes, eat the entire leaf except for large veins. Larvae younger ages Mole crickets (Gryllotalpa gryllotalpa) feed on humus and plant roots that grow into the nesting chamber. The main food of older larvae and adults are earthworms, insect larvae, underground parts of plants, which causes great damage to cultivated plants, especially in vegetable gardens and greenhouses.

In forms with strict attachment of individual stages of development to a specific host species, for example in aphids, “trophic polymorphism” is determined by the number of hosts. Complex life cycles with larval stages allow species to utilize more than one habitat or food resource. Sexual generations of bean aphids, for example, feed

leaves of euonymus, viburnum, and asexual ones, in the second half of summer - leaves of vegetable plants.

Age structures of populations are expressed as age spectra. Reflecting the age structure begins with establishing a basic age spectrum. The basic age spectrum acts as a reference against which the age states of the studied populations of a given species are compared. The age spectra of specific coenopopulations, as a rule, deviate from the basic, generalized version. Theoretically, the amplitude of these oscillations fits into the zone M±3α, where M is the average value relative amount(in%) of each age group, α – standard deviation (Zaugolnova, 1976). According to N.V. Mikhalchuk (2002), in the conditions of Brest and Pripyat Polesie, the basic age spectrum of the lady’s slipper is classified as single-vertex type with an absolute maximum in the integral group “v+sv”. It is characterized by the following ratio of ontogenetic groups (%): J - 3.0; im - 10.5%; v+sv - 39; g1 – 20.8; g2 – 11.0; g3 – 6.0; ss – 6.8; s – 2.9).

Basic age spectra have been developed for coenopopulations of many herbaceous species (Fig. ...). They are considered as one of the biological indicators of the species, and deviations reflect the state of a particular coenopopulation. Coenopopulations of the lady's slipper are assessed using these age spectra as “very good” (within the confidence zone of the base spectrum the characteristics of 7-8 age groups out of 8 identified are located), “good”, “satisfactory”, “unsatisfactory” and “threatening” (beyond the boundaries of the monitoring zone there are characteristics of 7-8 age groups) (Mikhalchuk, 2002).

There are four types of base spectra. Within each type, several options are distinguished depending on the methods of self-maintenance, the course of ontogenesis of individuals and the characteristics of its implementation in the phytocenosis (Zaugolnova, Zhukova, Komarov, Smirnova, 1988).

1. Left-handed spectrum. Reflects the predominance in the population of individuals of the pregenerative fraction or one of the groups of this fraction. Characteristic of trees and some groups of grasses (Fig.).

2. Single-vertex symmetric spectrum. The population contains individuals of all age states, but mature generative individuals predominate, which is usually expressed in species with weak aging.

3. Right-handed spectrum. Characterized by a maximum of old generative or senile individuals. The accumulation of old individuals is most often associated with the long duration of the corresponding age states.

4. Bimodal (two-vertex) spectrum. Two maxima are observed, one in the young part, the other in the composition of mature or old generative

plants (two modal groups). Characteristic of species with a significant life expectancy and a well-defined period of aging.

Herbaceous plants deciduous forests, according to O.V. Smirnova (1987), are characterized by different types of basic age spectra (table).

Table Distribution of herbaceous plants of broad-leaved forests by

types and variants of basic age spectra (Smirnova, 1987)

Methods of self-support	Types of base spectra
expectations and their options	(according to the position of the main maximum)
	I (p – g1 )*	II (g2)			III (g3–ss)
Seminal		Gravilat city-
	corydalis,	sky, rank of age

		Kashubian,
		oak forest face,
	intoxicating,	sedge
	Robert's geranium


	speckled
Vegetative
	blue onion	obnoxious
deeply rejuvenated
rudiments, deep and
shallowly rejuvenated-
new beginnings
shallowly rejuvenated-					It's common to whine
rudiments (phyto-					novena
cenotically incomplete		hairy,
member spectra)		woodsman many-
		year old,





			star-
		Ka lanceolate, Violet
	(deeply rejuvenated)
wifely rudiments)		Geneva
seed and vegetative
ny (deep and shallow
side-rejuvenated for-

seed and vegetative		bear onion,		Poagrass oak-
	(shallow	hoof euro-		equal, sedge
wifely rudiments)		Peisky, honey-		palmate,
				sedge

		flowering, in-

		ordinary,
		tenacious creep-

* - I – left-sided spectrum; II – centered spectrum; III – right-handed spectrum.

Depending on the ratio of age groups, invasive, normal and regressive populations are distinguished. The classification was proposed by T.A. Rabotnov (1950) in accordance with the three stages of development of a coenopopulation as a system: emergence, full development and extinction.

1. Invasive population. Consists mainly of young (pregenerative) individuals. This is a young population, which is characterized by the process of development of the territory and the introduction of rudiments from the outside. She is not yet capable of self-sustainment. These populations are usually characteristic of cleared areas, burnt areas, and disturbed habitats. They develop especially successfully in the field after continuous plowing. In addition to local species, invasive coenopopulations are formed by introduced woody species. Saskatoon serviceberry, viburnum-leaved bladdercarp, banksa pine, ash-leaved maple and some other species penetrate into natural undisturbed or slightly disturbed cenoses without significantly affecting them general structure. The implementation process is very complicated and involves a lot of waste. Self-seeding of balsam fir, including seedlings, juvenile, immature and virginal plants, under oxalis growing conditions amounted to 40 thousand specimens/ha (left-sided spectrum) (Fig.). Over 12 years it decreased to 14.0, and over the next 9 years its number decreased to 6 thousand specimens/ha. Once under the canopy of the tree layer, virgin plants are characterized by slow development,

many enter secondary rest. The transition of individuals to the generative state is gradual. The generative generation is in the stage of increasing vegetative and generative power. Gradually, the introduced population acquires a characteristic phenological appearance, usually forming on the basis of a small number of founder individuals.

2. Normal population. Includes all (or almost all) age groups of organisms. It is distinguished by its stability, the ability to self-sustain by seed or vegetative means, full participation in the structure of the biocenosis, and independence from the external supply of germs. These populations are either normally complete or normal incomplete. Populations with a full age spectrum characteristic formed indigenous climax communities.

3. Regressive population. In such populations, postgenerative age groups of individuals predominate. There are no young individuals. In this state, they have lost the ability to self-sustain, gradually degrade and die. Regressive populations of silver birch in forests include many of the oldest birch forests, in which the species does not regenerate under the birch canopy, and spruce undergrowth, which makes up its invasive population, develops abundantly. The only white fir coenopopulation in Belarus in the Tisovka tract (Belovezhskaya Pushcha) was in a degraded state, mainly due to the reclamation of the swamp massif.

Age states reflect the dynamic state of the population. In its development, it usually goes through invasive, normal and regressive stages. In each case, the age structure of the population is determined by the biological characteristics of the species and depends on environmental conditions. Year-to-year variability in the age composition of fine bentgrass

(Agrostis tenuis) reflects the rice….

The role of age structure in the life of a population is great. Different nutritional spectra of age cohorts soften intraspecific competitive relationships, use resources more fully, and strengthen population resistance to unfavorable factors environment, since individuals of different cohorts have different adaptive potential. Thus, young individuals of woody plants successfully endure harsh winters under snow, under the cover of fallen leaves and withered herbaceous plants. In snowless, harsh winters, the potential for survival is highest for seeds that are dormant. Juvenile plants resist drought by closing their stomata early in the day, using up absorbed carbon; mature trees use groundwater (Cavander-Bares and Bazzaz, 2000). Age heterogeneity is also important for the exchange of information between individuals and serves the purpose of continuity in the population.

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4.3. Age structure

Age structure determined by the ratio of different age groups of individuals in the population. Age, or ontogenetic, condition is defined as the physiological and biochemical state of an individual, reflecting a certain stage of ontogenesis. Individuals of the same age state are functionally similar, but may have different absolute or calendar ages. Absolute age is measured by the lifespan of an organism or a given cohort of individuals in a population from the moment the individual appears until the time of observation. In a population and in a cenosis, it is not the absolute age, but the age state that reflects the biological role of individuals, and therefore a comparative assessment of the role of species in the community is carried out based on them.

Age structure of plant populations. The basis for identifying the age states of plants is a complex of qualitative traits. The expression of ontogenetic states is mainly morphological changes, which are most easily visually captured and correlatively associated with other age-related changes in the body.

The concept of age as a stage of individual development of an individual formed the basis for numerous periodizations of morphogenesis. The classification of age states of plants by Rabotnov (1950) is generally accepted. According to his classification, plants are distinguished into 11 age states, corresponding to four periods of ontogenesis (Table 3). The ratios of the duration of these periods in different species are very different (Fig. 44).

Rice. 44. The ratio of the duration of pre-reproductive (7), reproductive (2) and post-reproductive (2) periods of ontogenesis in some species (according to A.V. Yablokov, 1987)

Dormant seeds– seeds (embryonic individuals), separated from the parent individual and, after dissemination, existing independently in the soil (on the soil).

Sprouts– small non-branching plants with the presence of embryonic structures (cotyledons, embryonic roots, shoots with small, simpler leaves than those of an adult plant) and mixed nutrition (due to seed substances, assimilation of cotyledons and first leaves). During aboveground germination, the cotyledons are carried above the soil surface; when underground (near oak) - remain in the soil. The first leaves (of spruce) are thin, short (up to 1 cm long), rounded in cross-section and often located.

Table 3

Classification of age states of seed plants (according to Rabotnov, 1950)

*Indices of age conditions are adopted according to A.A. Uranov (1973)

Juvenile plants - plants that have lost their connection with the seed, cotyledons, but have not yet acquired the features and characteristics of an adult plant. They are easy to organize. They have childish (infantile) structures. Their leaves are small in size, not typical in shape (in spruce they are similar to the needles of seedlings), and there is no branching. If branching is pronounced, then it is qualitatively different from the branching of immature individuals. They are characterized by high shade tolerance, being part of the herb-shrub layer.

Immature plants are characterized by transitional characteristics and properties from juvenile to adult vegetative individuals. They are larger, with pronounced branching, and develop leaves that are more similar in shape to the leaves of adult plants. The nutrition is autotrophic. At this stage, the main root dies off, adventitious roots and tillering shoots develop. Immature trees are part of the understory layer. In low light conditions, individuals are delayed in development and then die off. In young children, this stage, as a rule, is not recorded. In spruce it is usually observed in the fourth year of life. Isolation of immature plants is most difficult, and some authors combine them into one group with virginile plants.

Virgin plants have morphological features typical of the species, but do not yet develop generative organs. This is the phase of preparing the morphophysiological basis for achieving physiological maturity, which will come at the next stage. Virgin trees have almost fully formed features of an adult tree. They have a well-developed trunk and crown, and maximum height growth. They are part of the tree canopy and experience the maximum need for light.

Generative young plants characterized by the appearance of the first generative organs. Flowering and fruiting are not abundant, the quality of the seeds may still be low. Complex changes occur in the body to ensure the generative process. The processes of neoplasms prevail over death. The growth of trees in height is intensive.

Generative middle-aged plants reach maximum sizes, are distinguished by large annual growth, abundant fruiting, and high quality seeds. The processes of new growth and death are balanced. The apical growth of some large branches of trees stops, and dormant buds awaken on the trunks.

Generative old plants– plants, the annual growth of which is weakened, the indicators of the generative sphere are sharply reduced, the processes of death prevail over the processes of new formation. The trees are actively awakening dormant buds, and the formation of a secondary crown is possible. Seeds are produced irregularly and in small quantities.

Subsenile plants lose the ability to develop the generative sphere. Dying processes predominate; secondary appearance of transitional (immature) type leaves is possible.

Senile plants are characterized by features of general decrepitude, which is expressed in the death of parts of the crown, the absence of renewal buds and other neoplasms; possible secondary appearance of some juvenile features. Trees usually develop a secondary crown and the upper part of the crown and trunk dies.

Dying plants have single viable dormant buds, dead parts predominate.

The listed age-related conditions are characteristic of polycarpics. In monocarpics, the generative period is represented by only one age state, and the postgenerative period is completely absent. Age-related conditions are determined using specially developed diagnoses and keys (Fig. 45, 46).

Age structure of populations in animals. U Animals are usually distinguished between young individuals, yearlings, yearlings, adults and old ones. Some authors distinguish five age groups of animals: newborns (until the time of maturity); young (growing individuals who have not yet reached sexual maturity); sub-adults (close to puberty); adults (sexually mature individuals); old (individuals that have stopped reproducing). V.E. Sidorovich distinguished three age groups in otter populations in Belarus: young individuals (first year of life), semi-adults (second year of life), adults (third year of life and older). In the Belovezhskaya bison population, adults make up 57.8%, young animals (from 1 to 3.5 years) - 27.9, young of the year - 14.3%.

It is difficult to distinguish age groups in animals. Most often, attention is paid to the time of transition of an individual to the generative state. The age of sexual maturity occurs at different times in different species. In addition, the timing of maturation of individuals of the same species in different populations is also different. In some populations of ermine (Mustela erminea), the phenomenon of neoteny is manifested - mating of still blind 10-day-old females. Beluga females mature at 15–16 years, males at 11 years. Under favorable conditions, beluga can enter rivers to spawn up to 9 times. During the river life period, females do not feed. Repeated maturation is observed after 4–8 years (females) and 4–7 years (males). The last spawning occurs at the age of about 50 years. The post-reproductive period lasts 6–8 years. Much earlier, at 4 or 5 years of age, female polar bears reach sexual maturity. Reproduction continues until the age of 20, repeating on average every 2 years, the average litter size is 1.9 cubs. Age-related differences are most clearly manifested in species whose development occurs with metamorphosis (egg, larva, pupa and adult).

Rice. 45. Age conditions of Norway spruce (according to Yu.E. Romanovsky, 2001):

j- juvenile; im- g- generative

Individuals of different age groups in both plants and animals, inevitably developing in different conditions, differ markedly not only in morphological, but also in quantitative indicators. They have biological and physiological differences and play different roles in the composition of communities and in biocenotic relationships. In plant populations, seeds, for example, being dormant, express the potential capabilities of the population. Seedlings have mixed nutrition (endosperm nutrients and photosynthesis), juveniles and individuals of subsequent groups are autotrophs. Generative plants perform the function of self-sustaining population. The role of individuals in the life of the population, starting with subsenile plants, is weakening. Dying plants leave the population. During the process of ontogenesis, many species change their life form, as well as their attitude and degree of resistance to environmental factors.

Rice. 46. Age conditions of middle plantain (according to L.A. Zhukova, 1980):

j- juvenile; im- immature; v – virgin; g- generative young; g 2– generative middle age; g 3 - generative old; ss- subsenile; s – senile

In animals, differences between age groups are also very significant and species-specific. In populations of the bank vole (Clethrionomys glareolus), according to Shilov (1997), individuals of the spring and summer cohorts quickly mature, marry early, and are fertile, contributing to an increase in population size and an increase in its range. However, their teeth wear out quickly, they age early and live mostly 2–3 months. A small number of individuals survive until the spring of next year. As a rule, animals of the latest generations hibernate. They have small body sizes, a much smaller relative mass of most internal organs (liver, kidneys), a reduced rate of tooth wear, i.e., a sharp inhibition of growth is expressed. In addition, they have a very low mortality rate in winter. In terms of physiological state, wintering voles correspond to approximately month-old individuals of the spring-summer generations. They give birth and soon die off. Their descendants - individuals of early spring cohorts, distinguished by early maturation and fertility, quickly replenish the population thinned out during the non-reproductive period, closing the annual cycle.

Thanks to the biological characteristics of wintering individuals, energy costs are reduced to a minimum during the most difficult time for the population. They successfully “drag” the population through the winter. A similar pattern was noted in other rodent species. In steppe pieds (Lagurus lagurus), born in May, the average age of reaching maturity was 21.6 days, and in those born in October, it was 140.9 days. As Schwartz puts it, experiencing unfavorable conditions occurs in a state of “canned youth.” The increase in life expectancy of rodents of later cohorts is not due to survival in old age, but by prolonging the physiological period of adolescence.

The process of transition of a plant or animal from a virginal state to a generative state is determined by a specific genetic program and is regulated by many factors. For plants, this is primarily temperature, daylight hours, and position in the phytocenosis. The onset of maturity of individuals in Siberian fir (Abies sibirica) cenoses of the same age ranges from 22 to 105 years. It has been noted that the formation of the first generative organs in coniferous species occurs during the maximum growth of the tree in height, as well as during intensive radial growth of the trunk. The faster the growth curve goes up, the earlier the woody plant enters the reproductive phase. Physiological and structural changes in plants are associated with the maximum linear increase in height. Rapid growth allows plants to achieve a certain morphological structure and linear dimensions in a short time. With the attenuation of the culmination of height growth due to the redistribution of plastic substances, stable flowering and fruiting begins. Herbaceous plants also begin to bear fruit at a certain threshold value of vegetative mass and the development of storage organs.

According to M.G. Popov, as the amount of meristem begins to decrease and “the body acquires a shell, the armor of permanent tissues,” its ability to grow decreases, the process of generative development begins, and with further depletion of the meristem, aging occurs. The mechanism of this phenomenon is very complex and not fully understood. It is assumed that quantitative changes in metabolism lead to the activation of inert genes, the synthesis of specific RNAs and qualitatively new reproductive proteins. Yu.P. Altukhov showed: the greater the proportion of “heterotic” genes included in the processes of growth and puberty, the greater the energy expenditure of the organism in the pregenerative period of ontogenesis and the earlier puberty occurs.

Age spectra. Age structures of populations are expressed in the form of age spectra, reflecting the distribution of individuals in a population according to age states. The study of age structure begins with establishing a basic age spectrum. Basic age spectrum acts as a reference (typical) with which the age states of the studied populations of a given species are compared. It is considered as one of the biological indicators of the species, and deviations reflect the state of a particular coenopopulation.

There are four types of base spectra (Fig. 47). Within each type, several options are distinguished depending on the methods of self-maintenance, the course of ontogenesis of individuals and the characteristics of its implementation in the phytocenosis.

Left-handed spectrum reflects the predominance in the population of individuals of the pregenerative period or one of its age groups. Characteristic of trees and some grasses.

Single-vertex symmetric spectrum reflects the presence in the population of individuals of all age states with a predominance of mature generative individuals, which is usually expressed in species with weak aging.

Right-handed spectrum characterized by a maximum of old generative or senile individuals. The accumulation of old individuals is most often associated with the long duration of the corresponding age states.

Rice. 47. Types of basic spectra of cenopopulations (average indicators) (from L.B. Zaugolnova, L.A. Zhukova, A.S. Komarova, O.V. Smirnova, 1988):

A- left-sided (meadowsweet); b - single-vertex symmetrical (Valis fescue); V– right-sided (meadow fescue); d – two-vertex (feather feather grass)

Bimodal (two-vertex) spectrum has two maxima: one in the young part, the other in the composition of mature or old generative plants (two modal groups). Characteristic of species with a significant life expectancy and a well-defined period of aging.

Ratio of age groups. Based on the ratio of age groups, populations are distinguished between invasive, normal and regressive. The classification was proposed by Rabotnov in accordance with the three stages of development of a coenopopulation as a system: emergence, full development and extinction.

Invasive population consists predominantly of young (pregenerative) individuals. This is a young population, which is characterized by the process of development of the territory and the introduction of rudiments from the outside. She is not yet capable of self-sustainment. Such populations are usually characteristic of cleared areas, burnt areas, and disturbed habitats. They develop especially successfully in places after continuous plowing. In addition to local species, invasive coenopopulations are formed by introduced woody species. Saskatoon serviceberry, viburnum-leaved bladdercarp, banksa pine, ash-leaved maple and some other species invade natural undisturbed or slightly disturbed cenoses without significantly affecting their overall structure. The implementation process is very complicated and involves a lot of waste. Self-seeding of balsam fir, including seedlings, juvenile, immature and virginal plants, amounted to 40 thousand specimens/ha (left-sided spectrum) under oxalis growing conditions. Over 12 years it decreased to 14 thousand, and over the next 9 years its number decreased to 6 thousand specimens/ha. Once under the canopy of the tree layer, virginal plants are characterized by slow development; many enter secondary dormancy.

Population normal includes all (or almost all) age groups of organisms. It is distinguished by its stability, the ability to self-sustain by seed or vegetative means, full participation in the structure of the biocenosis, and independence from the external supply of germs. These populations are normal full-membered or normal incomplete. Populations with a full age spectrum are a characteristic feature of established communities.

Population regressive 2
It is more correct to call it a “regressive population”.

Characterized by a predominance of post-generative age groups of individuals. There are no young individuals. In this state, populations lose the ability to self-sustain, gradually degrade and die off. Regressive populations of silver birch in forests include many of the oldest birch forests, in which the species does not regenerate under the birch canopy, and spruce undergrowth, which makes up its invasive population, develops abundantly. The only coenopopulation of white fir in Belarus (Belovezhskaya Pushcha) found itself in a degraded state, mainly due to the reclamation of the swamp massif.

Age states reflect the dynamic state of the population. In its development, it usually goes through invasive, normal and regressive stages. In each case, the age structure of the population is determined by the biological characteristics of the species and depends on environmental conditions. It should be used to guide the exploitation of natural populations of animals and plants.

The significance of different qualities of age-related conditions. Different nutritional spectra of individuals of age groups soften intraspecific competitive relationships, use resources more fully, and increase the population's resistance to unfavorable environmental factors, since individuals of different age groups have different adaptive potential. Tadpoles, for example, are aquatic phytophages, frogs are zoophages leading a terrestrial lifestyle. Adults of the cockchafer (Melolontha hippocastani) feed on tree leaves, while larvae feed on humus and plant roots. Cohorts are confined to different soil layers and, depending on its temperature and humidity, and the availability of food, the beetles fly out at different times, which provides the population with numerous adaptive strategies. The food of the cabbage butterfly (Pieris brassicae), the largest among local garden whites, is the nectar of cruciferous plants, the food of the caterpillars is cabbage leaves. At the same time, young caterpillars, grayish-green, with black dots and a light yellow stripe on the dorsal side, scrape off the pulp of the leaf; grown individuals make small holes in the leaves; older caterpillars, colored green, with bright black spots and three bright yellow stripes, eat the entire leaf, except for the large veins. Younger larvae of the mole cricket (Gryllotalpa gryllotalpa) feed on humus and plant roots that grow into the nesting chamber. The main food of older larvae and adults are earthworms, insect larvae, underground parts of plants, which causes great damage to cultivated plants, especially in vegetable gardens and greenhouses.

Age heterogeneity is also important for the exchange of information between individuals and serves the purpose of continuity in the population.

4.4. Sexual structure

Sexual structure– numerical ratio of males and females in different age groups of the population. Characteristic of populations of dioecious individuals (expressed in the most clear form in arthropods and vertebrates) and dioecious plants, which temperate zone northern hemisphere are about 4%. Traditionally, the sexual structure of populations of seed plants is determined by the ratio of individuals with pistillate, staminate and bisexual flowers. The development program of pistillate and staminate flowers is quite complex. Flower sex is regulated by the concentration of auxins in plant roots, controlled by the level of genomic ploidy, as well as by a signal coming from the external environment. For example, in hemp (Cannabis sativa), in low light and lack of moisture, plants with bisexual flowers appear with a fairly high frequency.

Sex structure is dynamic, closely related to the age structure of the population and the living conditions of individuals. Primary sex ratio is determined during the formation of zygotes by genetic mechanisms based on the different quality of sex chromosomes (X- and Y-chromosomes) (Fig. 48). In mammals and many species of other animals, females are homogametic (XX set of sex chromosomes), and males are heterogametic (XY).

Rice. 48. Scheme of the genetic mechanism of sex determination using the example of gamete fusion in mammals (from I.A. Shilov, 1997)

In birds and butterflies, on the contrary, the heterogametic sex is represented by females, and males are homogametic. During the process of meiosis, different combinations of sex chromosomes obtained from different parents are possible, which determines the sex of each individual in the offspring. In this case, there is usually an equal sex ratio (1:1). The only representatives of mammals in whose populations there is a genetically determined excess of females are the forest lemming (Myopus schisticolor) and the hoofed lemming (Dicrostonyx torquatus). In these species, in addition to the wild-type X chromosome (X 0), there is a mutant chromosome that induces the development of individuals with the XY karyotype along the female path. These females are widespread in populations and are fertile.

However, during the development process, the potential capabilities of the fetus are disrupted by various reasons, and at birth the actual ratio of male and female individuals turns out to be different. This ratio among newborns and juveniles is secondary sex ratio. The mechanism of sex redetermination under the influence of environmental factors, physiological causes, different mortality rates of fetuses of different sexes, which are superimposed on genetic conditioning, is especially pronounced at the embryonic and larval stages of ontogenesis. Thus, in many species of reptiles, the temperature of egg incubation is of leading importance for the formation of sex. In crocodiles, an equal number of males and females appear when the temperature in the nest is 32–33 °C. At lower temperatures (below 31 °C) only females develop, at higher temperatures (above 33.5 °C) only males develop. In the sea worm (Bonellia viridis), the larvae that float freely in the water become females. The larvae, which attach on the 4-6th day of development to the proboscis of an adult female and are influenced by the substances she secretes, develop into males.

Changes in the number of male and female individuals also occur during the ontogeny of individuals in the population. As a result, a new pattern emerges among adult individuals in the population. tertiary sex ratio, which is determined by various reasons. It may be the result of differential mortality of males and females. Due to the increased mortality of male bison in Belovezhskaya Pushcha, since 1983, there has been a tendency for the number of sexually mature males to decrease. The sex ratio is 1:1.6, and among adults it is 1:2.3. There are more males in populations of rare (endangered) birds. Females often die in nests during incubation. Stress, big exercise stress shorten their life expectancy.

The sex ratio also depends on the developmental characteristics of the species. For example, polychaete (Ophryotrocha puerilis) and gastropod(Crepidula plana) at the beginning of puberty with small sizes the bodies are male, and as they increase in size they begin to produce eggs. In some fish species, young individuals function as males and older individuals function as females. An ecologically complex population structure in some species is achieved due to the presence of dwarf forms in the population along with individuals of normal size. Among the kunja (Salvelinus leucomaenis), dwarf males do not make the usual migration to the sea for other individuals. Reproduction occurs in at a young age. After reproduction, individuals do not die, but develop further like ordinary juveniles (Yablokov, 1987).

Ecological and cenotic conditions, especially trophicity and soil moisture, play a major role in determining sex in dioecious plants. Males are more dominant in extreme conditions at a low level of vitality, which was noted in coenopopulations of sorrel (Rumex acetosella) and other herbaceous species. Females are more demanding of soil richness. They prevailed and were noticeably higher, according to our data, on rich fresh soils in coenopopulations of stinging nettle. In some coenopopulations, female and male individuals form two canopies. The ratio of male to female Marchantia polymorpha depends on the degree of moisture. With increasing humidity, the proportion of males increases noticeably.

Sex ratios vary widely among species. In many mammals and fish, the tertiary ratio is 1:1, in humans the secondary ratio is 1:1, but with age it shifts towards women due to their longer life expectancy. The secondary sex ratio in penguin populations is 1:1, tertiary - 1:2. In the gray monitor lizard, there are 22 females for every 65 males. An excess of females is observed in lemming populations. U bats after wintering, the proportion of females sometimes decreases to 20%, and in some birds (pheasants, great tits) higher mortality is typical for males. According to F.S. Kokhmanyuk, in 1976, females predominated in the Minsk, Grodno and Armavir populations of the Colorado potato beetle (over 90%); in Gomel, Brest and Sochi - males (70–91%). The following year, the sex ratio in the Grodno population of the species was 1:1.

Populations exhibit an individual tendency for changes in the sex ratio. This phenomenon, very dynamic and multifactorial, leads to a complication of the population structure. Each population is characterized not only by a certain numerical ratio of male and female individuals in different age structures, but also by the proportion different types males and females, the proportion of sterile individuals, as well as individuals with different sets of sex chromosomes (Yablokov, 1987). The sex ratio determines the intensity of reproduction and the overall biological potential of the population (Shilov, 1997).

V.N. Bolypakov and B.S. Kubantsev, summarizing the material on the characteristics of the sexual structure of animals, distinguishes four types of dynamics of the sexual structure of the population.

Unstable sex composition characteristic of animals with a short life cycle, high fertility and mortality (among mammals it is characteristic of species of the order insectivores). Sex ratios (secondary and tertiary) change frequently in different habitats and over relatively short periods of time.

Male-dominated composition characteristic of predatory animals with a pronounced form of care for offspring, whose populations do not reach high densities.

Female-dominated composition observed in such animals, the males of which have a shorter life expectancy and unfavorable conditions partially die off. The life of females is longer, fertility is low (ungulates, pinnipeds).

Composition with relatively the same number males and females characteristic of highly specialized animals, often with high fertility (muskrat, mole, beaver, etc.).

Biological diversity of male and female individuals. Nature has taken the path of separating the sexes, allowing, as Schwartz (1980) puts it, amazing extravagance, dividing individuals of the species into two genetically different groups (males and females). Physiological differences lead to ecological diversity, which is a guarantee of maintaining population heterogeneity, especially in extremely unfavorable environmental conditions.

The biological diversity of male and female individuals is manifested in the degree of resistance to environmental factors, growth characteristics, timing of puberty, behavioral reactions, and lifestyle. Female plants are distinguished by their large size, length of shoots, size and shape of leaves, crown structure, better development root systems, higher regenerative capacity, as well as greater demands on the richness of the soil and its water regime. Due to the greater degree of water content in the tissues, they are more mesophilic organisms. Male individuals are characterized by greater drought resistance and sensitivity to the adverse effects of low temperature, infection, and toxic substances. Sex differences in animals have even been identified in relation to the accumulation of heavy metals, for example in male swimming beetles (Dytiscus marginalis). U individual species There are differences in nutrition, which reduces intraspecific competition. Thus, female mosquitoes (family Culicidae) are blood-sucking, and males either do not feed at all or feed only on dew or nectar. The unequal length of the beaks in males and females of some birds allows individuals of the species to feed on different insects, and the different shapes of the beaks make it easier, respectively, to jointly catch insects from under the bark.

M.G. Popov (1983) believed that the sexual process does not have the primary goal of reproduction and is characteristic of highly organized creatures, but even they, for example insects, can develop without fertilization. Popov considered it a “permanent apparatus of variability” that ensures adaptation.

Fundamentals of population ecology. Fedoruk A.T. Short course of lectures on ecology Age structure of plant populations

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Fundamentals of population ecology. Fedoruk A.T. Short course of lectures on ecology Age structure of plant populations

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