Synthesis and Computer Study of Population Dynamics Controlled Models Using Methods of Numerical Optimization, Stochastization and Machine Learning

The problems of synthesis and analysis of multidimensional controlled models of population dynamics are of both theoretical and applied interest. The need to solve numerical optimization problems for such a class of models is associated with the expansion of ecosystem control requirements. The need to solve the problem of stochastization is associated with the emergence of new problems in the study of ecological systems properties under the influence of random factors. The aim of the work is to develop a new approach to studying the properties of population dynamics systems using methods of numerical optimization, stochastization and machine learning. The synthesis problems of nonlinear three-dimensional models of interconnected species number dynamics, taking into account trophic chains and competition in prey populations, are studied. Theorems on the asymptotic stability of equilibrium states are proved. A qualitative and numerical study of the models is carried out. Using computational experiments, the results of an analytical stability and permanent coexistence study are verified. The search for equilibrium states belonging to the stability and permanent coexistence region is made using the developed intelligent algorithm and evolutionary calculations. The transition is made from the model specified by the vector ordinary differential equation to the corresponding stochastic model. A comparative analysis of deterministic and stochastic models with competition and trophic chains is carried out. New effects are revealed that are characteristic of three-dimensional models, taking into account the competition in populations of prey. The formulation of the optimal control problem for a model with competition and trophic chains is proposed. To find optimal trajectories, new generalized algorithms for numerical optimization are developed. A methods for the synthesis of controllers based on the use of artificial neural networks and machine learning are developed. The results on the search for optimal trajectories and generation of control functions are presented.The obtained results can be used in modeling problems of ecological, demographic, socio-economic and chemical kinetics systems.

The mound-building mouse (Mus spicilegus) in Western Podillia: expansion on the left bank of the Dnister

New findings of the mound-building mouse on the left bank of the Dniester in the interfluve of its tributaries—the Dzhuryn and the Nichlava (Chortkiv Raion, Ternopil Oblast)—are described. The presence of Mus spicilegus was established based on findings of food stocks common for this species in the form of mounds, which are easy to detect in the field and which can be clearly diagnosed. Both single mounds and their clusters were taken into account. The specifics of biotopic distribution, formation of food reserves, and the role in trophic chains of this species under conditions of the studied region are indicated. The mound-building mouse is one of the few rodent species that maintain a high abundance under conditions of intensive agriculture, which involves mechanical tillage several times a year and a significant level of chemical use. The distribution of the studied species is influenced primarily by two factors: the level of agricultural techniques in agricultural production (arable farming and crop care, quality of harvesting) and the distance from uncultivated areas. The mound-building mouse usually inhabits agricultural lands with a low level of agriculture (minimal chemicalization and mechanical tillage). These are lands allocated for private gardening or farming. Such lands have increased weeds and crop losses during harvesting, which creates a rich food base. After harvesting, such lands usually do not undergo long-term tillage. Results show that the settlement of arable lands comes from natural or other uncultivated areas, where the nuclei of populations are concentrated. In autumn, under the above favourable conditions, population growth is observed in adjacent cultivated lands, where winter food reserves are formed in the form of characteristic mounds. On large-area crops of monocultures cultivated by large agricultural firms, mounds are usually absent. The level of agro-technical pressure on the same area varies from year to year. This causes temporary instability in the appearance of mounds. They disappear where anthropogenic impact has re-emerged significantly and re-appear where there has been a weakening. The role of the mound-building mouse in trophic chains and in maintaining regional biodiversity is shown.

ENTROPY PRODUCTION AND STABILITY OF DYNAMICS IN MODELS OF OPEN EXPLOITED TROPHIC CHAINS WITH EXPLICIT RESOURCE AND OMNIVORY EFFECT

Connection between stability of stationary states and such a thermodynamic property as an entropy production is studied for open trophic chains with explicit resource and omnivory effect. Entropy production is minimal in stable steady states under condition of non-negativity for their components. Marine trophic chains with “microbial loop” serve as examples of that kind of ecosystems with vertical structure. One of them is the pelagial of the Okhotsk Sea in Russian Far East. Additional organic matter passing through the loop facilitates the entropy production decrease, more organized trophic functioning and less organic matter loss comparing to the chain without omnivory

Emergence of stable motifs in consumer-resource communities

ABSTRACTUnderstanding how and why complex communities can be stable has preoccupied ecologists for over a century. Data show that real communities tend to exhibit characteristic motifs and topologies. Despite a large body of theory investigating both ecological (niche partitioning) and evolutionary (speciation and extinction) mechanisms, a general explanation for why particular motifs are more common than others remains elusive. Here we develop a mechanistic framework that investigates the set of possible motifs that can emerge under minimal conditions of a nutrient-limited system with no external inputs, and no spatial heterogeneity. Focusing on consumer-resource communities structured by competition and predation, we find that the emergent motifs under these minimal conditions are vertical trophic chains that maximize energy transfer and biomass production. Not only are such motifs stable to perturbations of species’ abundances, but they are also robust to species additions and removals. Our findings provide a mechanistic explanation for why tri-trophic chains are overrepresented in real food webs. They suggest that, because they maximize energy transfer, and can emerge and persist under minimal conditions, vertical trophic chains may constitute the fundamental architecture of consumer-resource communities.

Some Considerations Regarding the Presence of Heavy Metals in Soil and the Human Body

Until now, there have been laborious researches regarding the presence of heavy metals in environmental factors but their effects have been studied less in the bio-geo-chemical circuits, respectively within the local trophic chains and the regional trophic networks. Naturally, the metals existing in the earth's crust enter the bio-geo-chemical cycles. In the cells of higher organisms, as we know, there is a fragile balance between the amounts of metals needed for catalytic processes and toxic doses to organisms. However, this balance is dependent not only on the concentration and variety of metals in the Earth's crust but also on the microbiological activity of environmental factors, responsible for the transformation of these metals into complex chemical substances that affect more or less the organisms, respectively their enzymatic activity. The vital-necessary, but also the non-vital mineral substances in their mobile forms, which may at one time be toxic to organisms, are significantly pushed out by anthropic activities into trophic chains. They are present in environmental factors such as soil, air, water, reach the body of plants and the body of animals. Plants and animals can bioaccumulate and concentrate in their bodies several chemical elements in the environment, regardless of their origin, which is then easily transferred through food circuits into the human body. Thus, through local trophic chains, respectively through regional trophic networks, contamination of the human body takes place. This requires the need for a measure of most likely high complexity to mitigate the effects with a strong impact on the health status, including that of the human psychic. In severe cases of contamination, behavioral manifestations, especially among the vulnerable population, are proven.

Стойкие органические загрязняющие вещества (СОЗ) в звеньях трофических цепей Азиатско-Тихоокеанского региона: краткий обзор литературы

Представлены современные исследования стойких органических загрязняющих веществ (СОЗ) в различных звеньях трофических цепей Азиатско-Тихоокеанского региона (АТР). Ключевые слова: СОЗ; АТР; пищевые цепи; моллюски; рыбы; птицы; млекопитающие. The modern studies of persistent organic pollutants (POPs) in various links of the trophic chains of the Asia-Pacific region (APR) are presented. Keywords: POPs; APR; food chains; shellfish; fish; birds; mammals.

The role of microbiota in paleoecosystems for forming the molecular profile of coals

Mass deposits of fossil coals can be formed in certain evolution periods of the Earth’s biosphere, and they are the result of biogeocenosis functioning. A unique combination of ecological factors leads to the emergence of specific biomes with short trophic chains, an imbalance in the carbon cycle and desynchronization in the flows of substance and energy. The molecular structure of coal is a complex conglomerate of various stable organic compounds of primary and secondary metabolites of biogeocenosis reducers. The molecular profile includes numerous classes of lowand high-molecular organic substances that interact closely with each other. Multiple classes are not endless, the interaction is not chaotic, and their number and relationships are determined by paleoecologic patterns and coalification. Even a small fragment of the profile includes valuable information about the genesis of individual compounds and the biogeochemical situation when forming the coal bed. Microbiota impact does not end with a period of mortmass accumulation, which is never fully mineralized. In the coalification process, favorable environmental conditions may arise for the rebirth of the microorganisms’ lives in coal beds.

Microplastic vector effects: are fish at risk when exposed via the trophic chain?

In aquatic organisms, trophic transfer is a relevant exposure route for microplastics (MPs). Despite their relevance, effect studies on fish exposed via trophic chains are currently very scarce. MPs are known to contain many chemicals that could be transferred to organisms and induce deleterious effects. However, there is currently no consensus on whether MPs represent a significant exposure pathway to chemicals in contaminated habitats. Here, we exposed three-spined sticklebacks (Gasterosteus aculeatus) to polyethylene MPs via prey ingestion, in a one-month experiment. MPs were either pristine or spiked with chlorpyrifos (CPF), and a CPF control was included to compare vector effects of MPs and natural prey. Following exposure, we assessed AChE activity and fish behavior (feeding, locomotion, environment exploration and reaction to the introduction of a novel object). No effect was observed in fish exposed to pristine MPs. CPF accumulation was observed in fish exposed to CPF-spiked MPs (MP-CPF), confirming the vector potential of MPs. However, CPF accumulation was more important in fish exposed to CPF via prey. In fish exposed to MP-CPF, we observed significant AChE inhibition and hyperactivity, which could result in increased vulnerability to predation. CPF organ distribution differed between groups, suggesting that chemical exposure via MPs could alter organ distribution of chemicals. This can result in a change in the organs most at risk, likely increasing intestine exposure.