Biotic Regulation and the Concepts of Genetic Adaptation and Nutrient Limitation
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Biotic regulation and the concepts
of genetic adaptation and nutrient limitation


On this page we attempt to discuss the conceptual principles of the modern biological science. We also analyse how these principles relate to the modern environmental problems of the humanity. Undertaking such an effort, one cannot escape making generic and sometimes simplified statements. Here we did it with purpose, that is, we have sacrificed complexity to the transparency of logical presentation.

Also, by being as clear-cut as possible, we aimed at facilitating or even provoking a critical analysis of the views presented. Any comments, remarks, suggestions and, in particular, criticisms are welcome in our on-line discussion area.


General remarks
Incompatibility of the concepts
The evidence: Are the traditional interpretations unambiguous?
        a) Genetic adaptation
        b) Limiting principle
Evidence which finds no traditional explanation
        a) Climate instability
        b) Species discreteness
Why are the concepts of genetic adaptation and nutrient limitation so commonly accepted?
The importance of re-evaluation of the theoretical bases of modern biology


General remarks

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Modern biological theory rests on the two conceptual principles, the nutrient limitation principle and the principle of genetic adaptation. The nutrient limitation principle refers to the statement that functioning of the biota is limited by the availability in the environment of the chemical elements used by the biota. In its more general form, the limiting principle proclaims limitation of any standing biological quantity by certain resource (e.g. population number of a certain species is limited by the available food). Changes in the abundance of the nutrients (resources) govern biological processes.

The genetic adaptation principle refers to the statement that biological species adapt genetically to changing environmental conditions. At any moment, any population is composed of individuals with slightly (or substantially, depends on the definition) different genetic programs (genotypes). The genotype(s) allowing their carriers to produce the maximum number of offspring are by definition the most fitted to the corresponding environment and enjoy the highest frequency in the population. When the environmental conditions change, different genotypes may appear to be most fitted. This will result in a directional change of the genetic composition of the population and, ultimately, in biological evolution.

Below we dwell on the following issues:

We show that the limiting principle and the genetic adaptation principle are logically incompatible with the biotic regulation concept.

We show that the whole bulk of evidence that is usually interpreted in favour of the limiting principle and the genetic adaptation principle can be easily interpreted within the biotic regulation concept.

We show that there are important lines of evidence which can be interpreted exclusively within the biotic regulation concept and which contradict the limiting principle and the genetic adaptation principle.

We briefly discuss the reasons of why, in spite of that, the limiting principle and the genetic adaptation principle are so widely accepted.

We discuss the reasons of why we believe that it is so important and urgent to re-evaluate the theoretical bases of the modern biological science.


Incompatibility of the concepts

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Both the limiting principle and the genetic adaptation principle are logically incompatible with the biotic regulation concept.

According to the biotic regulation concept, the concentrations of all life-important are created and maintained by the biota itself. Consequently, they cannot limit the biota's functioning. If some concentration of any nutrient becomes such that it hinders normal functioning of the biota, the biota is able to change its concentration as needed. For example, the terrestrial ecosystems are known to compensate for the physical soil weathering in this manner.

Vice versa, if there is nutrient limitation, no biotic regulation is possible. Nutrient limitation implies that the biota may only react to changes in concentrations of the limiting nutrient, increasing or decreasing its productivity. Other nutreinte are assumed to be present in the environment in excess. Changes in concentrations of such non-limiting nutrients cannot influence the biota's functioning.

This attitude is currently widely employed in the analysis of global carbon cycle. It is assumed that the oceanic biota does not react to the human-induced increase in concentrations of atmospheric and, consequently, dissolved carbon, because its functioning is limited by other nutrients (nitrogen, phosphorus, iron etc.). So, the oceanic biota is excluded from considerations of the global carbon cycle changes. On the contrary, the terrestrial biota which is believed to be fertilised by the excessive carbon (limiting nutrient), is given an important role of a considerable carbon sink.

We stress that neither the nutrient limitation principle nor the genetic adaptation principle represent issues of purely academic interest. On the contrary, they are widely involved into solving the modern problems of the humanity like, for example, the analysis of the global carbon changes. An important practical implication of the genetic adaptation principle is the well-known concern of conservation biologists about preserving the genetic polymorphism of the species, which is thought to be absolutely necessary for the species to adapt to and survive in the continuously and currently rapidly changing environment.

The genetic adaptation principle is also incompatible with the biotic regulation concept. By regulation we understand not a mere impact of the biota on the environment, but maintenance of the environment in a certain stable state and compensation by the biota for all random deviations of the environmental conditions from that optimum. In order to regulate the environment the biota must possess some information about what environment to maintain and how to do it. This information may only be of genetic nature and should be written in the genomes of the biological species.

If the environment occasionally deviates from its optimal state (e.g. under influence of external abiotic factors), the genetic information of species forming ecological communities should ensure a compensating reaction of the community. As a result, the environment will be returned back to the optimum. A full analogy of this process is a disease of a multicellular organism. When some external agents of biological (e.g. microbes) or physical nature disturb the internal milieu of the organism, the genetic information, which is contained in its cells governing their functioning, ensures processes aimed at the organism's recovery.

Within such an approach, no genetic adaptation to changing environment is possible. For the biota it is only possible either to compensate environmental changes and return the environment back to the state, characteristics of which are written in its genetic program, or to change the genetic program fitting to a new environment.

The logical conclusion is that either the biotic regulation concept, or the principles of genetic adaptation and (nutrient) limitation do not describe the natural biota correctly and cannot survive together in the biological theory having equal ranges of application.


The evidence: Are the traditional interpretations unambiguous?

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Now we turn to the analysis of the general types of evidence usually thought to be unambiguously interpreted in favour of the limiting and genetic adaptation principles.


a) Genetic adaptation to the contents
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The well-known line of evidence interpreted in favour of genetic adaptation is represented by phenomena that are to a smaller or larger degree related to the artificial selection. In its most generic form, this evidence can be conceptualised as follows.

There is a population of organisms living in environment A. This population is characterised by a given genetic composition, i.e. a certain distribution of frequencies of different genotypes. Let genotypes A be most abundant in environment A. It further happens that this population (or some part of it) finds itself in a different environment B. After some period of time one observes a different distribution of genotype frequencies, with the most abundant genotypes B differing from genotypes A.

These observations are interpreted in that sense that individuals with genotypes B are better adapted to environment B, than those with genotypes A. Their better adaptation has caused the change in the genetic composition of the population, which was brought about by the change in environmental conditions.

Let us now see how the same observations are interpreted within the biotic regulation concept. In short, we will argue that the observed genetic changes appear as the result of decay of the initial normal genetic information of the population.

In a more detailed way, the explanation runs as follows. Biological species forming an ecological community contain in their genomes information about how to keep their environment stable. This information is prevented from decay (erosion) by the stabilising natural selection. Within a certain range of environmental conditions, individuals with normal genetic information enjoy the highest competitiveness and are most abundant. This allows the community to perform a correct and efficient buffering response to any perturbation of the environment.

However, there is naturally a threshold level of perturbations beyond which the biotic regulation is helpless. An example of such critical perturbation is the modern anthropogenic disturbance of the biosphere. As a rule, in nature such perturbations are either extremely rare or transient. Let us call the environment which is perturbed beyond the threshold unnatural. Each species in the community may be characterised by its own set of threshold environmental characteristics.

In the unnatural environment the regulatory potential of the species is useless by definition. Hence, the normal genotypes carrying information about biotic regulation are no longer associated with the highest competitiveness. As a result, the genetic information of the species starts to decay. New genotypes with partially eroded genetic information that would have been forced out from the population in the natural environment, now get a chance to persist. If the environment is not restored to its normal state by other species of the community, the genetic decay may thus proceed until the very viability threshold of the species.

By definition, any process of decay is accompanied by an increase in variability (entropy) of the decaying characteristics. On a quantitative level, the process of decay of the genetic information of species in an unnatural environment will be pronounced as increased genetic polymorphism in the population as compared to normal environmental conditions. (For example, the domestic mammals (horses, cows, sheep) and the man himself demonstrate protein heterozygosity levels from four to ten times higher than the average value for the class of mammals).

It may happen occasionally that under unnatural conditions certain newly appeared decay genotypes will correspond to a higher viability than normal genotypes or other decay genotypes. Such genotypes may then temporarily become more abundant. Also, in different unnatural environments different decay genotypes will be abundant. However, this can hardly be interpreted as genetic adaptation, because in any case the abundant genotypes are products of erosion of genetic information. To give an extreme example, under conditions of unbearable noise only deaf animals will survive, under conditions of unbearable light intensity - only blind ones etc. It is not an adaptation, however, because animals with such defects - unlike the normal ones - are unable to ensure a long-term stable existence of the population. This can be empirically tested.

So, we have shown that the change in genetic composition of the population does not necessarily represent a new state of genetic adaptation. It may be a manifestation of genetic decay of the genetic program of a species placed under unnatural conditions.

Here we present some additional considerations. In particular, we address the following possible question: "What is the difference between the above blind animals whom you characterise as 'products of genetic decay' and the species who had lost vision in the course of evolution, for example some fishes living in dark caves? Isn't it just a question of definition?"



b) Limiting principle to the contents
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The simplest summary of evidence interpreted in favour of the limiting principle is as follows. When an additional amount of a certain nutrient is introduced into the ecosystem, it leads to increased productivity of the corresponding ecological community. Phenomena of this kind are widely used in agriculture, where the substances that ensure the enhanced primary productivity of fields and pastures are called fertilisers.

It might seem that one can do nothing but accept the interpretation provided by the limiting principle. Functioning of the biota is dependent upon the availability of major nutrients (carbon, nitrogen, oxygen, phosphorus, iron etc.). All these elements enter biochemical reactions in non-random (stoichiometric) proportions determined by the organisation of the living matter. The least abundant nutrients limit the rate of biochemical reactions. Increase or decrease of concentrations of the limiting nutrients increases or decreases the biological productivity.

Before proceeding to the alternative explanation of the observed phenomena that is provided by the biotic regulation concept, we would like to note the following. In order to determine which nutrient is the limiting one, one calculates the relative ratios of nutrient concentrations and compares it with those found in the living matter. Such a consideration implies that 1) biological production of organic forms of nutrients is proportional to the concentrations of nutrients in the inorganic form, 2) the proportionality coefficients (their inverse values are sometimes called resistances) are the same for all nutrients and 3) the biota is unable to change the resistances. There is no evidence testifying to the generality of these statements. For example, although some nutrient can be present in the environment in a relative abundance, the corresponding value of resistance to its production may be so high, that the biota perceives this nutrient as the least abundant, or vice versa. (The large value of resistance means that it is 'difficult' for the biota to produce organic forms of this nutrient.) At present, these considerations are ignored by the biological theory.

Now we turn back to the alternative explanation of the above descirbed phenomena of increased biological productivity. In order to regulate the environment, the natural biota has to produce certain work aimed at compensation for possible deviations of environmental conditions from the optimum. The intensity of such work is naturally proportional to the primary productivity. If the productivity is small, the stabilising work will be also small!

It is natural therefore that in most cases the biotic reaction on perturbation of the environment is accompanied by increased primary productivity. For example, the increased concentrations of inorganic phosphorus or nitrogen in lake communities lead to increased primary productivity. It is commonly assumed that these experiments (as well as similar experiments with incubation of marine biota in bottles with elevated concentration of nutrients) have a single and unambiguous interpretation, corresponding to phosphorus (or nitrogen) limitation of primary productivity.

In reality, however, the observed initial growth of primary productivity may have two explanations: 1) it is either limitation of primary productivity by phosphorus or nitrogen 2) or it is a stabilising reaction of the biological community to a perturbation of its environment, where the perturbation is manifested as the increased concentration of the nutrient, while the stabilising reaction is assumes the form of increased productivity. It is aimed at decreasing the concentration of phosphorus or nitrogen down to the non-perturbed optimal level. These two possibilities can be discerned by a long-term continuation of the experiment, which, as far as we know, is rarely, if ever, performed.

If it is indeed a stabilising reaction of the community, then, if the perturbation is artificially supported for a long time in spite of the community's efforts, the stabilising potential of the community may be exhausted and the community may degrade together with its environment. If, on the contrary, it is the limitation of primary productivity by phosphorus or nitrogen, then the community will keep the increased productivity for ever if the corresponding nutrient is continuously supplied. That is, the community's functioning will stabilise at another level of primary productivity and in a different stable environment (with elevated level of phosphorus or nitrogen). No environmental degradation is to be expected.

An analogy of such a long-term experiment can be found in agriculture, where the nutrient limitation principle is used most widely. It is well-known that the primary productivity in the agricultural systems is currently sustained by continuous increase in inorganic nutrient supply and is accompanied by continuous degradation of environmental conditions, e.g. soil erosion. It is well-known that in order to keep the yield high and stable, it is necessary to increase the amount of applied fertilisers from year to year. It means that no stable state is possible under arbitrary concentrations of inorganic nutrients. This is in perfect agreement with predictions of the second interpretation of the observed growth of primary productivity in response to external perturbation, namely, that it is a stabilising reaction of the community aimed at relaxation of the environment to the non-perturbed state.

It is useful to ask a question: why does the ecosystem function in a stable mode with their initial, non-perturbed concentration of, e.g., inorganic nitrogen but, when additional nitrogen is added by humans, rapidly spends it up and returns to the initial state? Why does not it spend up the initial concentration as well? The answer is unambiguous: because the ecosystem forms and maintains the initial, non-perturbed nitrogen concentration itself.

We have seen so far that the increased biological productivity in response to the addition of certain nutrients may be interpreted as a stabilising reaction of the ecological community to the environmental perturbation, in accordance with the biotic regulation concept. Similar logic can be applied to the analysis of changes in population numbers of organisms, the existence of which is believed to be limited by certain resources. Here you find more about it.

We have also allocated some place for discussion of the situation with the marine biota. Application of the limiting principle to description of functioning of the marine biota currently underlies all models of the global carbon cycles and, consequently, is of direct relevance to ecological problems that may affect everybody. Here we discuss whether this application is scientifically justified.

So far, we have discussed the evidence that is usually interpreted in favour of the genetic adaptation and nutrient limitation principles. We have pointed to some inconsistencies in the traditional interpretations and suggested interpretations following from the biotic regulation concept. Now we turn to the lines of evidence that find no traditional explanation and can be exclusively explained by the biotic regulation concept.


Evidence that finds no traditional explanation

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This evidence forms the theoretical foundation of the biotic regulation concept and we have already discussed it elsewhere. Here we present a shortened discussion of these issues.

Generally speaking, the principles of genetic adaptation and nutrient limitation depict life as a set of objects which characteristics are shaped in the process of random survival of organisms in the ever changing environment and which functioning is governed by simple biochemical regularities associated with the availability of nutrients. Such a consideration does not exclude the possibility of a biotic impact that might be occasionally imposed on the environment. However, this impact is chaotic in the sense that it might be both stabilising and destabilising with respect to the current state of the environment. In other words, the principles of genetic adaptation and nutrient limitation are incompatible with the idea that life creates and maintains a life-compatible environment itself.


a) Climate instability to the contents
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If so, why have the environmental conditions on Earth remained suitable for life during the last four billion years of life existence? Modern biological theory, resting on the adaptation and limitation principles, does not pose such a question. It takes for granted that the set of suitable for life environmental conditions on Earth is physically stable. In other words, it is implicitly assumed that there are physical regularities that prevent, for example, the global mean surface temperature from a rapid rise to, say, +600 ° C, like on Venus, which would be followed by inevitable extinction of all life. (The available evidence shows that the global mean surface temperature has during all the time of life existence remained within the temperature interval from +5 to +25 degrees Celsius.)

However, the analysis of physical characteristics of the Earth's climate does not reveal any physical mechanisms that might explain such a stability, given the remarkable changes of all the climate-determining characteristics like, for example, the solar constant or the atmospheric composition of the planet. On the contrary, there are strong indications that the modern climate of Earth with its liquid hydrosphere is physically unstable with respect to rapid and irreversible transitions to the state of either complete glaciation of the planet's surface or complete evaporation of the hydrosphere. Both are unfit for any life.

This means that it is the life itself that has been supporting the climate and other environmental characteristics within the life-compatible interval. The widely discussed possibility of the existence in the geological past of the so-called snowball Earth (i.e. the state of the planet with an extensive snow cover) does not disprove this statement. On the contrary, it is impossible to explain involving physical mechanisms alone, why the proposed snowball Earth returned to its current state instead of getting covered by snow all over. The last possibility is more realistic due to the strong positive feedbacks associated with changes in albedo and greenhouse effect.

Our analysis of the global carbon cycle shows that at present the characteristic time of environmental relaxation performed by the natural (undisturbed by humans) biota is of the order of decades. In other words, any perturbation of the environment (e.g. CO2 inputs) decreases e-fold in about 10 years. During the geological periods of often glaciations covering up to 25% of the land surface, the global area occupied by the biota was reduced no more than twofold. The relaxation time increased accordingly (i.e. the global biota became less powerful and compensated environmental perturbations more slowly). Even if during the catastrophic periods of the Earth's history the area occupied by the global biota were reduced by ten or hundred times, this would correspond to the relaxation time reaching values of 100 to 1000 years, which is a negligible term on a geological scale. Hence, the biotic regulation (if it exists) was not switched off during any period of life existence.

As the humans disintegrate the natural ecological communities in the course of civilisation development, the stabilising regulatory mechanism of the natural biota becomes less and less efficient. Currently this is manifested in the growing frequency of extreme climatic events like floods, draughts, hurricanes, tornadoes etc. However, if the threshold of anthropogenic disturbance of the natural ecosystems is passed, this may switch the climate to either of the two physically stable states that are life-incompatible.

Given this, it is remarkable that the climate stability phenomena receive so little attention within the modern scientific community, theoretical biologists included. The biological theory just accepts like axioms statements that, if re-evaluated, may completely undermine its current theoretical foundations.


a) Species discreteness to the contents
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Another line of evidence that is neglected by the biological theory, is the bulk of data on species discreteness. Having examined the available paleorecord, one discovers that every species is represented by a set of morphological forms that exist practically unchanged or change very little and in a continuous fashion during the whole period of species existence, which is of the order of several million years. Then this species disappears from the record (becomes extinct). Its place is then taken by another, closely related species, which is separated from its predecessor by a gap in a variety of morphological characteristics. In other words, the morphological forms of organisms that succeed each other in the paleorecord, do not intermingle continuously with each other, but form discrete pools.

How can this be explained from the point of view of continuous genetic adaptation to randomly changing environment? There is no evidence suggesting that the physical characteristics of the environment on Earth are changing in a pulsing manner every several million years. Moreover, speciation do not necessarily occur in pulses, there is always a background nearly constant rate of extinction and speciation.

It is remarkable that there is a huge number of publications in theoretical biology that contain models of genetic adaptation in fluctuating environments, in patchy environments, in constant environments etc. But there is hardly a single publication (we would be happy to be referred to one) where the morphological discreteness of the paleospecies is addressed from the theoretical point of view.

According to the biotic regulation concept, genomes of species contain information that, taken altogether, enables the corresponding ecological community to maintain its environment in a stable state. If the external physical characteristics of the environment change, the community initiate processes aimed at their compensation. Given this, it is natural that the species retain genetic and, consequently, morphological constancy during the most time of their existence. Random genetic changes that might lead to a more efficient regulation of the environment, appear very rarely, which explains the large, geological scale of species' existence and the low frequency of speciation events.

We note that, on the contrary, genetic changes that lead to erosion of genetic information, are very common. This explains the short scale of genetic changes associated with artificial selection.


Why are the concepts of genetic adaptation and nutrient limitation so commonly accepted?

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Bearing in mind everything said so far, the above question indeed deserves a special consideration.

During the course of human history the biological science has been predominantly applied to solving the tasks of feeding humans and their medical treatment. Accordingly, the empirical evidence for developing the biological theory was taken from studies of separate species rather than ecological communities. In particular, the concepts of genetic adaptation and nutrient limitation both emerged largely as the result of scientific research into domesticated plants and animals.

The concept of genetic adaptation would not have been formulated by Charles Darwin without extensive analysis of artificial selection. Similarly, formulation of the concept of nutrient limitation owes much to agricultural and related land use practices (Liebeg's principle, 1840), where it proved evident that the productivity of certain plants can be enhanced by use of chemical or organic fertilisers. However why should one expect organisms operating within natural ecological communities to behave the same as individuals in artificial conditions?

The point is that the global environmental problems of the humanity are of a very recent origin. They arose when the exponential anthropogenic disturbance of natural ecosystems approached the critical threshold, beyond which the biotic regulation potential is destroyed. While the biological theory still uses categories of the past, when the environment was seemingly stable by itself and the only task was, as we already noted, that of feeding and curing the humans. Within this context the two conventional principles we have examined remain perfectly valid, i.e. as they apply to the functioning of separate organisms in environments dominated by human activity. However, when the same biological science is applied to global change science and applied to examining the interactions between natural biota and global environmental conditions their validity must be called into question.


Importance of the re-evaluation of the theoretical bases of modern biology

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We have argued that the biotic regulation concept provides a sounder basis for global change science than does the perspective resulting from jointly considering the concepts of nutrient limitation and genetic adaptation. If humanity were not experiencing the acute ecological problems of today, the difference between these two views on the nature of life could remain of purely academic interest. However the two paradigms lead to drastically different implications in terms of what needs to be done to address the global environmental crisis.

One interpretation based on the generally accepted paradigm is that the global biota will adapt to anthropogenic transformation as it has been adapting to spontaneous environmental changes during the four billion years of life existence. Given this, a solution to the problem of long-term environmental stability is sought in the creation of environmentally-friendly technologies that reduce the impact of modern industrial production and consumption. This solution provides incentives for the further cultivation of the remaining natural biota and other biospheric resources, and does not recognise or value their environmental stability functions. The idea that a technological solution to the problem of global environmental security is even in principle possible is not self-evident and demands rigorous scientific investigation. At best a technological solution is a necessary but insufficient condition.

A very different path of development compatible with long-term environmental safety follows from our proposed alternative paradigm view. It lies in the conservation and restoration of a substantial part of the Earth's biosphere in its natural non-perturbed state in order to enable the stabilising potential of the natural biota of Earth with respect to the global environment will continue to function. This strategy sets a ceiling to the exploitation of biospheric resources, and places strict guidelines on the kinds and extent of allowable economic activity and ultimately the global human population number.

Thus there is a very essential difference between the alternative strategies for human development implied by the two opposing scientific paradigms. The development path offered by the biotic regulation concept provides a precise definition of what constitutes sustainable development and the pre-requisites for a sustainable way of living. In contrast, sustainability as defined by the conventional paradigm allows complete cultivation of the biosphere and reliance on technological means of ensuring environmental stability.

Irrespective of the validity of the biotic regulation concept, the feasibility of the technological option is entirely unproved and should not be considered as a valid option until such time as scientific investigations yield a positive and conclusive answer. Only then will humanity be free to choose between the two alternative strategies of development. Until such research is conducted, there is no free choice but only one safe strategy of development for human civilisation, namely, that of relying on the conservation of a major part of the natural biota of Earth. The technological path of development, along which modern civilisation is now spontaneously moving, is burdened with the long term risk of global ecological catastrophe following the breakdown of the unique regulatory mechanism of the natural biota.

The issues we have raised require that global biogeochemical cycles are considered jointly with phenomena such as genetics, speciation, natural selection, and community organisation. This is rarely undertaken due to the increasing specialisation of modern science. Consequently few attempts are made to envisage an integrated scientific theory of the total Earth/life system, and no one discipline takes responsibility to investigate the inconsistencies that arise when principles from different scientific fields are considered simultaneously.

All this gives good grounds for the world scientific community to urgently re-evaluate the biological principles we have critiqued here. We welcome everybody to discuss these issues.


Main page in English   6 October 2001.