Rasnitsyn, 2008. Theoretical foundations of evolutionary biology - 01

A.P. Rasnitsyn. Theoretical Foundations of Evolutionary Biology // V.V. Zherikhin, A.G. Ponomarenko, A.P. Rasnitsyn. Introduction to Paleoentomology. Moscow: KMK, 2008. 371 p. 1.1. THE PROCESS OF EVOLUTION 1.1.1. SYNTHETIC THEORY OF EVOLUTION

1.1.2. EPIGENETIC THEORY OF EVOLUTION 1.1.2.1. Main Propositions 1.1.2.2. Adaptive Compromise 1.1.2.3. Problems

  1.2. METHODOLOGY OF PHYLOGENY, TAXONOMY AND NOMENCLATURE 1.2.1. PHYLOGENY  1.2.1.1. Group Analysis 1.2.1.2. Character Analysis  1.2.1.2.1. Analysis of Differences 1.2.1.2.2. Analysis of Similarities 1.2.1.3. Computer Cladistics

1. THEORETICAL FOUNDATIONS OF EVOLUTIONARY BIOLOGY The evolution and systematics of insects in this book (and in subsequent volumes of this series) are reconstructed based on assumptions that are sometimes not very familiar to domestic biologists raised on the synthetic theory of evolution. Therefore it seems useful to provide here a brief justification of my views on the evolutionary process and on the ways of studying its results. A more detailed exposition of this viewpoint is given in other works (Rasnitsyn, 1987, 2002, 2005; Rasnitsyn, 1996, 2006). 1.1. THE PROCESS OF EVOLUTION The notion of a complete and final victory of Darwinism in modern biology does not fully correspond to reality: alternative views persist and continue to develop. Among other evidence for this, for example, is the appearance of the voluminous book by Yu.V. Chaikovsky (2003) with the promising title “Evolution”. Therefore, before dissecting competing paradigms of selectogenesis (the line of thought that is often labeled with the unsuccessful term Darwinism, see below), I will have to somehow justify the choice of this particular direction. Various concepts are offered as alternatives to selectogenesis. Chaikovsky (2003) names four systems of views on the evolutionary process: Darwinism, nomogenesis, Lamarckism and Joffrurism (after one of the famous early evolutionists E. Joffrur Saint-Illier). This classification is unsuccessful both terminologically and substantively. It is logical to name after the founder the doctrines whose essence consists in interpreting canonical texts (Christianity, Buddhism, Marxism), but not systems of scientific views, because the logic of scientific inquiry almost inevitably leads to a revision of a greater or lesser part of the statements of previous authors. As a result, anecdotal situations sometimes arise. The same Yu.V. Chaikovsky, despite his vehement anti‑Darwinism, acknowledges not only selection (in a heavily truncated form) and the inheritance of acquired characteristics (in a heavily expanded form), but also pangeneisis, and turns out to be a greater Darwinist than those who are considered and consider themselves followers of Darwin. Therefore, outside this section I will, as far as possible, avoid using such names. In substance, the proposed classification is unsuccessful in the sense that its subdivisions overlap to the point of indistinguishability. For nomogenesis, a distinctive feature is the special attention to the regular character of the evolutionary process, but, as is known, evolutionary research in all directions is occupied with searching (not unsuccessfully!) for such regularities (see, for example, Rautian, 1988). Even if nomogenesis is narrowed to the recognition of a broad repeatability of evolutionary pathways (parallelisms, Meyer’s refrains, etc.), then, as will be seen later, this approach is perfectly compatible with selectogenesis, which recognizes the important role of selection. Joffrurism is defined as a direction that gives special significance to ontogenetic transformations as a mechanism of evolution: equally this applies to the epigenetic version of selectogenesis (Woodgington – Schmalhausen – Shishkin – Rasnitsyn – Tikhomirova, see below). The limited effectiveness of selection, whose recognition Chaikovsky points out as an important trait of nomogenesis, Joffrurism and Lamarckism, also belongs to the key propositions of epigenetic selectogenesis (see below). The situation with Lamarckism is somewhat more complex. Two essentially independent statements are linked to this term – the progressive character of the evolutionary process (increasing complexity and refinement of organisms, their structure and functioning) and the inheritance of acquired characteristics. The problem of progress naturally falls within the problematics of selectogenesis (again I refer to my work: Rasnitsyn, 1971). The inheritance of acquired characteristics was long considered incompatible with Darwinism (although Darwin himself thought otherwise), but when the discovery of retroviruses demonstrated a feedback from phenotype to genotype bypassing selection, it turned out that nothing serious for selectogenesis had happened. Indeed, if it is advantageous for an organism to fix a certain modification in DNA and a mechanism for such fixation can be developed (for example, with the involvement of retroviruses), why could selection not implement such a mechanism? The other matter is that DNA exists precisely to store information reliably and, accordingly, to exclude external influences on its structure as much as possible; therefore any mechanism deliberately exerting such influence is dangerous for the primary function of DNA. In my view, this is why the inheritance of acquired characteristics does not belong to the routine mechanisms of the evolutionary process. Thus, in the above interpretation Lamarckism, Joffrurism and nomogenesis do not constitute a principled alternative to selectogenesis. At the same time it is clear to everyone that at least Lamarckism and nomogenesis are something completely different from modern Darwinism (i.e., selectogenesis), although their fundamental (essential) distinction has not yet been formulated. As for Joffrurism, it is described insufficiently to place it on any side of the watershed that will be discussed. In my opinion, the essential difference between selectogenesis on the one hand, and Lamarckism and nomogenesis on the other, lies in the relation to the source of purposiveness. A structure (including a system of actions) that appears, at least superficially, to have been created specifically to perform a certain function that is useful in a given context is called purposive (adaptive). Therefore, explaining the origin of purposiveness must take into account the future function of the emerging structure (system): in a certain sense the future function shapes the structure. The emergence of a substantially new purposive structure (system) is conceivable only through direct goal‑setting, i.e., with the participation of reason (roughly, a human or a god), or through memorizing and reproducing a successful choice, i.e., by selection. The efficiency of selection as a method of finding a purposive solution was demonstrated by W. Ashby (1964) with a homeostat model. For application to the evolutionary process this model was modified as a parallel homeostat, differing in that stepwise variables are used not sequentially, as in Ashby, but simultaneously: the individuals serve as phenetically and genetically distinct entities (Rasnitsyn, 1971). Another striking example of a parallel homeostat, according to modern conceptions, is the immune system of homeotherms, as described by Chaikovsky (2003) on pp. 189‑190. An indisputable mechanism of making purposive decisions is reason. It is also indisputable that human‑type reason arises late and cannot be the source of evolutionary purposiveness. Since substantial purposiveness of evolution is apparently not denied by anyone, the discussion may involve either reason, an immanent life, or a pre‑existent one, i.e., a non‑natural (roughly, divine) nature of evolutionary purposiveness. In my view, this is where the watershed lies between selectionism, which refuses to view evolution as a product of intelligent activity, and nomogenesis and Lamarckism, which assume a non‑natural (alternative to selection) source of progress (Lamarckism) or purposiveness (nomogenesis). Since invoking non‑natural factors in evolution, in my view, is legitimate only within the framework of faith and is incompatible with science, the choice of selectogenesis for me is inevitable. In modern selectogenesis theory two main approaches compete – synthetic and epigenetic. The synthetic theory of evolution, better known to our biologists, can be described as reductionist, reducing whole‑level effects to phenomena at the level of its elements – primarily elementary genetic factors and their frequencies in populations. The opposing epigenetic theory can only very loosely be labeled anti‑reductionist: its adherents try to understand the properties of the evolutionary process based on certain properties of the whole organism, primarily its ontogeny. In substance this is a further development of the holistic approach to evolution (Smuts, 1926, cited in Smuts, 1987). The relationships between the synthetic and epigenetic hypotheses have been specifically examined by M.A. Shishkin (1987, 1988a, 2006) and D.L. Grodnytsky (2000, 2002). Relying on their results, I will attempt to present my view of this problem. 1.1.1. SYNTHETIC THEORY OF EVOLUTION The synthetic, more precisely – population‑genetic theory of evolution (because the synthesis there is more proclaimed than achieved) treats inheritance, i.e., the ability to stably reproduce phenotype and its characters in successive generations, as a property of special elementary carriers – genes, now identified with chromosome loci and further with DNA segments (cistrons, etc.). Accordingly, the evolutionary process is represented as the dynamics of allele frequencies in populations, controlled by selection (differential reproduction of phenotypes). Phenotypic characters arise and change as a result of mutations and recombination of genes. Since all these changes lack an inherent initial purposiveness, it is selection that shapes the composition of populations and organismal properties, doing so with an accuracy limited only by stochastic (probabilistic) factors. Apart from randomness, the only obstacle to a full correspondence between the organization of living beings and the demands of selection is gene flow, which homogenizes population structure at a level responding not to local but to averaged selection characteristics. According to these views, the organization of living beings appears as soft clay in the hands of selection, a set of characters freely shuffled by selection. Consequently, from this standpoint the evolutionary process appears uniform – at least to the extent that environmental and selective variations are uniform. Uniformity of evolution is consistently disrupted only by divergences and extinctions, which in the considered worldview constitute the sole natural basis for constructing a system of organisms. The synthetic theory, of course, acknowledges both gene pleiotropy (one gene affecting multiple traits) and trait polygeny (multiple genetic determinants of a single trait), so that each trait actually depends on the entire genome. However, these acknowledgments are essentially declarative, because the total interdependence of structural and functional elements of the organism and, consequently, the lack of any relatively constant contribution of a gene to fitness make it impossible to reduce the evolutionary process to elementary genetic, let alone molecular‑genetic, events. These simplifications are not harmless: they lead to mismatches between theoretical predictions and observational results. Let us present some of these discrepancies. First, we turn to the rates of the evolutionary process, assessed by the speed of origination and extinction of taxa of a given rank. A taxon is the sole concept whose very meaning is an attempt at an integrated assessment of similarities and differences among organisms. In practice, however, the comparability of taxa of the same rank across different groups is ensured by nothing but the intuition of systematists (see below), so this method of estimating evolutionary rates is imperfect. Yet we have no other way to compare rates of organismal evolution. Although the assessment of differences in taxonomic ranks is imperfect (subjective), it is more informative than a more objective assessment based on characters. It is well known that externally identical differences can be achieved by such disparate means and represent manifestations of transformations of organization on vastly different scales, so that using them to estimate evolutionary rates would only be misleading. This conclusion is especially vividly confirmed by material on evolution in island conditions and in the early stages of taxon evolution (the phenomenon of archaic diversity). Here grotesque forms with unbalanced organization arise quickly and easily. They often differ in traits that, in normal (stabilized) groups, characterize taxa of much higher rank (see below for details). At the same time, paleontological assessment of taxonomic evolutionary rates yields results and reveals trends that are unlikely to be attributable to the incomparability of taxa of the same rank in different groups (Rasnitsyn, 1987). According to the synthetic theory, the evolutionary process is driven mainly by the same factors and mechanisms that operate in population genetics. Then the speed of macroevolution should obey the same regularities as the speed of change in gene frequencies in population genetics. This speed, in turn, is determined by the magnitude of the flow of adaptively competent genetic variations (changes relevant to selection) that pass through the evolving ensemble. Consequently, the speed should be higher the higher the mutation rate and the faster the generational turnover, the larger the population size and the greater the mobilizable variance reserve. Paleontological material does not allow a direct assessment of most of the parameters used in population genetics. Some of them can nevertheless be indirectly estimated in fossils – to the extent that they correlate with other traits such as size, taxonomic affiliation, etc. In particular, if the genetic approach to evolution is valid, its speed should be minimal in mammals, which have relatively slow generational turnover and small populations (due to relatively large body size), maximal in unicellular organisms and intermediate in invertebrates. In reality, however, numerous paleontological data show the opposite pattern (Rasnitsyn, 1987). Moreover, differences are very large even at the species level, although this taxonomic category is considered comparable across groups. For example, the half‑life of fauna (the time at which half of the species are modern and half extinct) for large mammals (proboscideans and ungulates) is 0.2 Ma, for small mammals 0.5 Ma, for birds and fish 0.7 Ma, for insects 3–7 Ma, for molluscs 3.5–5 Ma, for diatom algae – 15 Ma. The half‑extinction time (analogous to half‑life, the time for half of the original number of species to disappear) is smallest for elephants (0.18 Ma), on average 0.54 Ma for mammals, 3.5 Ma for bony fish, 1.3 Ma for graptolites, 4.2 Ma for echinoderms, 7 Ma for bivalve molluscs, 5 Ma for planktonic foraminifera, 18–24 Ma for benthic foraminifera, 5.5 Ma for diatom algae, 9 Ma for dinoflagellates. At higher taxonomic levels the differences are similar but often more pronounced. For instance, the half‑life of fauna for mammalian genera is 4 Ma, for birds 10 Ma, for reptiles 20 Ma, for fish 30–50 Ma, for insects 40 Ma, for molluscs 60 Ma, for foraminifera 230 Ma. These figures do not call genetic predictions into question. Selection is absolutely automatic: if individuals differing in fitness appear in a population, they will be consistently selected in full accordance with the principles of population genetics. To the extent that these differences are heritable, the varying reproductive contribution of individuals will automatically lead to changes in the population’s hereditary structure. Hence, the distribution of evolutionary speeds predicted by genetic theories must occur in nature – to the extent that the overall flow of genetic variation over the long term correlates with the flow of selected (enhanced adaptive) heritable changes. Confirmation is provided by well‑known differences in typical selection speeds among domestic animal breeds, plant varieties and microbial strains. Equally indicative are the occasionally observed maximal rates of insect evolution, such as on the Hawaiian island of 0.5 Ma (Rotondo et al., 1981) where, after 17 colonizations, 46 species of the beetle genus Plagithmysus (Gressit, 1978) arose, i.e., at least one speciation event occurred on average every 150–200 kyr. G.H. Shaposhnikov almost produced a new aphid species in a single season (see below). At the same time it is evident that, overall, the distribution of evolutionary rates at the species level and above, in a first approximation, is opposite to that predicted by population genetics. This means that population‑genetic constraints are not constraints for the evolutionary process. Roughly speaking, the flow of overall genetic variability is evolutionarily excessive even in populations of large mammals, let alone in other, more numerous and faster‑reproducing organisms. The rate of change at the supra‑population level (the rate of evolution) must be regulated by some other factors. The question of what these factors might be will be considered later. Here we can only conclude that the level to which the synthetic theory of evolution attempts to reduce the evolutionary process, and thereby explain it, does not meet the expectations placed upon it and does not provide the anticipated explanations – at least regarding the paradox of evolutionary rates. There are also other data groups that do not fit within the framework of the synthetic theory of evolution. If the organization of living beings is soft clay in the hands of selection or a set of characters freely shuffled by selection, then its outcomes should be predictable to the extent that the conditions under which evolution occurred are known. Anti‑selectionists have shown on numerous examples that this is not the case (see, for example, Lyubyshev, 1982). Even closely related forms in seemingly similar conditions can behave completely differently.The most paradoxical example of this is the extremely extravagant spotted hyena in the reproductive sphere and the quite ordinary in this respect closely related striped hyena. Even less explainable from the synthetic point of view is the widespread, if not universal, discreteness of biological diversity. In this system of views, only one form of discreteness is natural—the discreteness of an amphimictic species under conditions where gene exchange is sufficiently intense to unify the composition of populations despite local variations in selection. But then there should be a good correlation between the degree (completeness and antiquity) of isolation and the degree of divergence. This is not observed in reality: the retarding (difference-leveling) influence of gene exchange on the rate of divergence cannot be confirmed. S. S. Schwartz (1980) came to this conclusion, comparing mammalian species with different propensities to form isolates. The seemingly obvious counterexample of island speciation actually pertains to a different context (see below). The discreteness of species in parthenogenetic and asexual organisms, which lack gene exchange, is completely inexplicable from the standpoint of the synthetic theory of evolution. Comparison of closely related bisexual and parthenogenetic species in rotifers (Mayr, 1974) and in seed beetles (Ivanova, 1978; V. V. Zherikhin, personal communication), of bisexual and asexual species in protists (Yu. Poljansky, 1957; Ramashka, 1977), in lower algae (V. Poljansky, 1956), and in ferns (Faggell, 1990) has shown that unisexual and asexual species are as discrete as bisexual ones. No less indicative is the long-term (millions, tens, and possibly even hundreds of millions of years) evolutionary stasis at the species and genus levels, when exchange of hereditary information is out of the question. Thus, populations of four or five of the thirty Australian species of campodeid insects (Campodea) are indistinguishable at the species level from populations on distant continents and islands—Kalimantan, Japan, South Africa, Europe (Tuxen, 1967). Campodeids are not resistant to desiccation and do not leave the soil, so transcontinental migrations are practically excluded for them. Explaining their distribution, it is difficult to avoid references to continental drift, especially since a classic “drift” range is known for campodeids (Delamarentulus tristani Silv. is distributed on both coasts of the Atlantic Ocean, in Costa Rica, and in West Africa; Tuxen, 1963). But from this it automatically follows that the age of the species is estimated at tens of millions of years. There are also more direct indications of the great antiquity of some species. Thus, in the fauna of Eocene Baltic amber (an age of at least 40 million years), several insect species and about ten mite species are now known that are indistinguishable at the species level from modern ones; persistence over 10–20 million years is even more common (Zherikhin, 1999). Findings of diverse Pliocene galls, indistinguishable from galls induced by modern insect species on the same plants, are much younger (3–5 million years), but they are no less important (Zherikhin, 2002a). The morphological specificity of a gall is determined by the biochemical effect of the gall-forming insect on the tissues of the host plant. Therefore, the morphological stability of galls proves the biochemical stasis of insects over millions of years. Many of these finds come from Northern Europe, so we are dealing with species that survived the glacial period (although mostly through migrations), but did not change even biochemically. Thus, stasis lasting millions of years is realized not only in the absence of gene exchange, but also despite undeniable deep, possibly even catastrophic, changes in conditions. The record-holder, however, is the tadpole shrimp Triops cancriformis (Schaffer), which has hardly changed since the early Triassic (about 230 million years ago), and the question of the species status of Permian populations remains unresolved (Tasch, 1969). This conclusion is confirmed by molecular clock data for two morphologically barely distinguishable Japanese populations of another species, T. longicaudatus (LeConte): they indicate divergence of the species about 15 million years ago. For other species of this genus, including T. cancriformis, divergences are dated to 25–45 million years (Suno-Uchi et al., 1997). No less understandable in this system of views is the common phenomenon in which higher taxa turn out to be more discrete and demonstrate clearer relationships than species. Indeed, species diverged relatively recently, had less time for divergence than higher taxa, and therefore should have preserved more traces of how divergence proceeded (see below for details). All that has been said, in my opinion, convincingly shows a serious mismatch between the population-genetic approach with its derivatives (the synthetic theory of evolution and the biological species concept) and the results of observations. Therefore, it is time to turn to another system of views on the evolutionary process. 1.1.2. EPIGENETIC THEORY OF EVOLUTION 1.1.2.1. Main Propositions Unlike the synthetic theory, the epigenetic theory sees the evolutionary process primarily as a process of evolutionary transformation of ontogeny (Shishkin, 1987, 1988a, b, 2006; Rautian, 1993). In this context, special attention is paid to the integrity of ontogeny in the sense that both the process itself and its result (the structure of the organism at successive stages of its development) are far more stable than any individual factors and developmental processes. Normal development is equipotential and capable of relaxing (suppressing, absorbing, leveling) a very wide range of influences and disturbances, both external and internal, including the results of various errors and violations of normal development. Thus, what is inherited (stably reproduced in subsequent generations) is normal ontogeny (norm of reaction) as a whole, not individual traits. In addition to the norm, there is a multitude of diverse deviations (aberrations) of development with unstable reproduction, which are rarely realized under normal conditions. Under unfavorable conditions, when the mechanisms protecting the norm are disrupted or overcome—as a result of strong external impact or internal causes (developmental errors)—development proceeds along an aberrant (deviating and unstable) path. Since endogenous aberrations of development arise easily not only during sexual but also during parthenogenetic and asexual reproduction, their occurrence is a realization of the hidden heterogeneity of the population, not the emergence de novo of some genetic changes. The epigenetic theory considers aberrations as material for selection, capable of creating a new adaptive norm on this basis. This process is easier to describe within the metaphor of the epigenetic landscape. Normal ontogeny represents a stable (stabilized) sequence of closely linked individual epigenetic processes. More or less isolated segments of this sequence are called creods. If one imagines a creod as a deeply sunken valley in some landscape, down which the ontogenetic process flows (Fig. 1), then aberrations will be gentle lateral side-valleys raised at the edges of the main one. For an aberration to be realized, i.e., for ontogeny to exit into the lateral valley, either a strong external impact on the developing organism, pushing it onto the lateral valley (Fig. 2a), or a change in the landscape itself, leveling the bottom of the valley (an additional aberrational change, Fig. 2b), or both together (Fig. 2c) is required. [IMG_1] Fig. 1. A section of the epigenetic landscape showing the height gradients of the walls (thresholds of stability) of a creod at the points of branching into aberrational valleys. A1, A2 — aberrational valleys, N — main valley (creod) (after Shishkin, 1987) Aberrations are poorly stable (“non-heritable”; the more stable ones are often called modifications), but they are constantly, though unpredictably in detail, reproduced in the population, since the epigenetic landscape with corresponding lateral side-valleys is the adaptive norm of the species. Therefore, despite their weak heritability, it is precisely aberrations that serve as material for selection. If an aberration proves useful, selection will selectively preserve those epigenotypes that reproduce it more stably. In other words, the advantage will go to those epigenotypes where the corresponding valley is deepened, and the level of its bottom at the junction with the main valley is closer to the bottom of the latter. If at the same time the main valley is also leveled below the fork (i.e., if the stability of the former norm decreases), the former aberration will have a chance to become a new norm. If the former norm retains its significance, then both norms will stabilize, and a mechanism of ontogenetic switching between them will be developed. In cases where this mechanism uses an environmental signal for switching, we obtain typical modification variability. Where a genetic signal is used (e.g., recombination), we obtain one of the forms of Mendelian inheritance. In this way, Mendelian traits arise in nature (e.g., ordinary mechanisms of sex determination) and in the laboratory (e.g., in the process of stabilizing pure lines). [IMG_2] Fig. 2. Relationships between the structure of the epigenetic landscape and the character of damaging impact: a — deviation into a lateral valley due to strong external impact (long arrow); b — the same deviation under the action of a strong mutation causing disruption of a creod; c — intermediate state (after Shishkin, 1987) For the epigenetic theory of evolution as a whole, the fixed (“memorized”) spectrum of possible developmental pathways (creods and their aberrations) in the adaptive norm, i.e., the epigenetic landscape, is the essence of the living organism, its ontogenetic potential, that which determines the existence of the organism and with which selection works. The purely genetic level (genes and their alleles, dynamics of their frequencies in the population, mutations, recombination, etc.) lies much deeper and does not determine the specifics of evolutionary processes. Just as the specifics of what happens at the macro level cannot be derived from the processes and laws of the quantum-mechanical level. “Genes come and go, but creods remain”: it is well known that traits are more stable than the genes and alleles that supposedly determine them. The ontogenetic processes in terms of inheritance are considered in more detail by M. A. Shishkin (1987, 1988a, 2006). For us, however, another aspect of the problem of ontogeny evolution is more important. 1.1.2.2. Adaptive Compromise 1.1.2.2.1. Formulation and Justification The integrity of the organization of living beings has a tremendous influence on the character of their evolution. At the morphogenetic level, this influence manifests itself in the fact that due to the deep interdependence between changes in different creods and, as a consequence, between changes in different properties and traits of the organism, creods turn out to be highly stabilized. They are difficult to change beyond the limits of normal intraspecific variability, which is itself stabilized by selection of previous generations. Therefore, evolution, i.e., a successful exit beyond the limits of the normal, stabilized epigenotype, occurs with difficulty, infrequently, and with little predictable result. In other words, in the hands of selection, the organization of living beings turns out to be a fragile, capricious material, evolutionary transformations are more or less jump-like, and the resulting biodiversity is more or less discrete. This discreteness is not absolute, and even where it exists, we do not always manage to easily grasp it (due to overlapping limits of stabilized variability, see below). But it exists and is very widespread, which biologists, and especially systematists, are not too inclined to emphasize, focusing on exceptions and difficult cases. The existence of exceptions is quite natural. The stabilized epigenotype (adaptive norm) includes a certain, more or less wide spectrum of variability, exactly as emerged in the result of selection of preceding generations, just like the modal characteristics of the phenotype. The spectra of normal variability of close species can overlap, creating problems for systematists, even if the epigenotypes themselves differ discretely at the same time. The problem is that we still do not know how to see, outline, and measure the epigenotype itself, and not only its external manifestations. The epigenotype is inaccessible to direct observation, but it is deduced from available data almost as reliably as an atom or a neutrino. And it is inaccessible to direct observation precisely because the epigenotype is a very complex system of relationships and interactions. But, like an atomic charge, the epigenotype essentially determines the properties and behavior of its embodiments—individuals, species, or other taxa. Therefore, it can even be defined as the materialized entity of all these embodiments, which is in a sense a return to essentialism—but to an essentialism of a significantly different kind than Plato’s, since the essence here is recognized as material and knowable. But let us return to the evolution of the epigenotype. The high connectivity of the epigenotype and the entanglement of its evolutionary changes are conveniently analyzed within the framework of another metaphor—the metaphor of adaptive compromise (Rasnitsyn, 1987). Indeed, the stability of a balanced epigenotype can be regarded as one of the consequences of systems theory, in particular, its assertion that no system can be optimized simultaneously for more than one parameter. It is no accident that a penguin cannot run and fly, a stilt cannot swim, and an ostrich hardly swims well. Optimization of real systems is possible only as a search for a compromise between contradictory requirements for the optimization of various parameters. For living beings, whose organization is permeated with various correlations and interdependencies, the compromise between different adaptive functions must be especially tense. Therefore, a stable epigenotype must be organized on the principle of a deeply worked-out compromise between contradictory needs for the maximum optimization of all adaptive functions. The attitude toward a living being as an adaptive compromise is not something new. E. Mayr apparently meant precisely this when he wrote that “the epigenotype of a species, its system of developmental canals and feedbacks is often so well integrated that it opposes changes with wonderful persistence” (1974, p. 353). Ideas close to the struggle (competition) of parts in the organism were expressed much earlier by V. Roux and A. Weismann (Weismann, 1905), before them in the form of the principle of compensation or equilibration—by J.-B. Lamarck and G. St. Hilaire (see: Darwin, 1991, p. 128), and even earlier as the principle of economy—by Aristotle (1937). The metaphor of adaptive compromise is important because a wide range of relatively easily verifiable consequences can be derived from it. The most general of them is the difficulty of changing a well-balanced organization. Of course, this difficulty is not absolute, and to the extent that changes are possible, the loss of adaptive value of some function will lead to the reduction of the systems providing it. The loss of an adaptation, a trait that has lost its significance, is naturally explained by the fact that the reduction or disintegration of unnecessary systems allows additional optimization of other systems that have retained their adaptability. For us, however, the difficulty of restructuring a once-formed compromise, the existence of barriers on the path of changing the established organization, is more essential. Apparently, the evolutionary landscape should not be represented as it is usually depicted: in the form of adaptive peaks separated by valleys of reduced fitness and connected by ridges along which an evolving group can gradually move from a disappeared peak to a preserved one. A more plausible model is F. R. Schram’s model (Shram, 1983)—a system of basins separated by barriers of adaptive instability. The difficulty of overcoming the stability of a once-achieved successful compromise predetermines many important properties of the evolutionary process: the already mentioned unevenness and sluggishness (entanglement) of evolution, the discreteness of living beings, the low evolutionary efficiency of elimination. Many of the questions to which the synthetic theory cannot give an intelligible answer—such as the unevenness of evolution, the widespread evolutionary stasis, the absence of a visible influence of population-genetic factors on the rate of the evolutionary process—all these effects turn out to be natural and expected when the process is considered from the standpoint of adaptive compromise. However, as should be expected, their place is taken by other problems, no less difficult to resolve. Evolution proceeds, despite all barriers, but at the cost of the extinction of many groups that failed to successfully overcome these barriers. Let us try to understand under what conditions and in what way this happens, how a balanced epigenotype can be transformed into another, also balanced one. Traditionally postulated mechanisms of the evolutionary process, based on the interaction of intraspecific and interpopulation polymorphism with isolation, do not give an answer to the question posed. It has been convincingly shown that reproductive isolation is not only unnecessary for evolution, but does not even stimulate it (Gritsenko et al., 1983, ch. 7). By all the laws of population genetics, the universality of intraspecific and interpopulation polymorphism in combination with the monstrous pressure of normal elimination (see below) should lead to constant and rapid evolution with a characteristic distribution of rates (high in lower organisms and low in higher ones, see above). This is also not observed. From the contradiction considered, I can draw only one conclusion: under normal conditions, intraspecific polymorphism does not contain evolutionarily competent traits. Simply put, none of the variants of phenotypic and genotypic organization that are regularly realized in populations of a species, under normal conditions, has an evolutionarily significant advantage over other variants. All animals are equal, and there are none more equal among them.How can this be, if polymorphism sometimes affects seemingly vital organs and structures? The answer, apparently, is the same: all existing variants exist because they are consistent with the available epigenetic system, i.e., they do not disrupt its stability, but they are also incapable of creating a new stability (some other, not necessarily better, but a different stabilized system). In other words, intraspecific polymorphism together with modification variability at its supraorganismal level performs the same function of system stabilization in an unpredictably variable environment that ontogenetic regulation, physiological reactions, and behavior perform at the organismal level. Since analysis of individual factors does not provide an answer to the question of the specific mechanism ensuring the evolutionary process, let us try to approach it from the other side. Let us analyze the conditions under which evolution actually proceeds, and moreover, proceeds relatively rapidly. Although reproductive isolation, as already noted, is not an important evolutionary factor under normal conditions, it is well known that under conditions of isolated islands, water bodies, etc., evolution proceeds especially rapidly and often leads to the emergence of strongly modified, even grotesque forms. S. S. Shvarts (1980), who specifically analyzed this paradox, concluded that the reason lies in the reduced intensity of competitive relations in poor, unfilled (in evolutionary time scale) island biocenoses. Specifically, the evolutionary role of niche underfilling, according to Shvarts, is that weakened competition makes possible rapid unilateral specialization. This is an attractive interpretation for the concept of adaptive compromise: an ancestral species, upon entering a depleted island biocenosis from the mainland, finds itself in conditions that are mitigated along many parameters and allow additional optimization of functions that remain under strict environmental control, at the expense of others that are not controlled by selection as strictly. In reality, as we shall see, the matter is more complex and not reducible to weakening selection, but for now let us use this non-strict term. The described model of island evolution is also interesting because it corresponds to the concept of inadaptive evolution by V. O. Kovalevsky (Rasnitsyn, 1986). More importantly, however, it demonstrates a sufficiently real mechanism capable of overcoming, breaking the stability of a well-balanced adaptive compromise that retards evolution. Naturally, the question arises whether a similar mechanism can act not only during island colonization but also in some other situations.

[IMG_3] Fig. 3. Correlation between extinction and origination in animals: proportion of families recorded in the paleontological chronicle: A – for the last time, B – for the first time (after Newell, 1967, from Grant, 1980) To answer this question, let us consider some other cases of a group’s transition into similar conditions—will accelerated evolution and its similarity to inadaptation be observed there as well, i.e., an increase in the range of changes combined with their unilateral nature and imbalance? Transition into relatively free, unfilled ecological space is characteristic, for example, of the early stages of evolution of many taxa, and the paleontological chronicle indeed confirms that at early evolutionary stages, both the frequency and scale of evolutionary changes and the intensity of extinction of newly formed inadaptive groups increase as niches are filled. It is known that mass extinctions and diversifications often occur almost simultaneously. Moreover, periods of diversification follow periods of extinction (Fig. 3), which confirms the fact that liberation of ecological space by extinct groups stimulates the evolution of survivors. Acceleration of evolution at early stages of a taxon’s history is more specifically demonstrated by the fact that the age of a genus approximately coincides with the age of many of its species (Shvarts, 1980); this shows that a significant part of divergence occurs at the earliest stages of the emerged taxon’s evolution.

The law of archaic diversity (Mamkaev, 1968) describes sharply increased organizational variability at early stages of a taxon’s evolution, so that species and genera at that time may differ in characters that later characterize families and orders. No less characteristic for the stage of archaic diversity is the low evolutionary stability of early members of the taxon, reflected in the abundance of short basal branches on almost any phylogenetic scheme constructed using rich paleontological material (Fig. 4).

[IMG_4] Fig. 4. Phylogenetic tree of scorpionflies (order Panorpida). After Novokshonov (Novokshonov, 2002), with modifications All of the above allows us to conclude that a group’s transition into conditions of a depleted biocenosis and an unfilled ecological niche indeed triggers evolution, and moreover, substantially inadaptive evolution. In this case, the emergence of euvadaptive groups, i.e., harmonious ones adapted to filled biocenoses and tense competitive relations, can be linked to subsequent tightening of conditions and intensive extinction of most newly arisen groups (those incapable of quickly transforming from inadaptive to euvadaptive).

Let us analyze the famous experiments of G. Kh. Shaposhnikov (1961, 1965, 1966, 1978). In these experiments, aphids Dysaphis anthrisci maicopica Shap. were transplanted from a suitable host plant, Anthriscus nemorosa MB., first to a less suitable one (Chaerophyllum bulbosum L.), and then to a previously completely unsuitable one (Ch. maculatum Wild.). As a result, within a few generations the aphids not only changed morphologically but also acquired reproductive incompatibility with their own species and incomplete compatibility with D. chaerophyllina Shap., the original consumer of Ch. maculatum. In Shaposhnikov’s experiments, selection was clearly unilateral and unbalanced (inadaptive). Indeed, in the experiment, the ability to feed on the new host plant was for some time the only vital complex of adaptation, while all others receded into the background. Of course, the experiment was not completed, but if it had been continued and transferred to nature, we would probably have been able to observe the next stage of evolution. Namely, the testing of the emerging group by comprehensive, euvadaptive selection, for which all aspects of adaptation are important—feeding, reproduction, individual stability of different ontogenetic stages under varying population densities, competitive ability, etc. There is little chance that a specific population would survive this test, but chances do exist. Let us return to the problem of mild conditions and weakened selection. Can the conditions in Shaposhnikov’s experiments be considered harsh? At different stages of the experiment, larval mortality ranged from 15–22% to 53–75%. It seems high, but given the fecundity value (36.6 larvae from one parthenogenetic female; data only for the final stage of the experiment), it means survival of at least about 10 larvae in the offspring of each female and, consequently, almost a tenfold population increase per generation. In other words, mortality in these experiments was quite moderate—obviously due to the fact that the experimenter’s care eliminated enemies of aphids and other unfavorable influences as much as possible. It is not surprising that the lines in the experiment proved quite stable and could be maintained for 50 generations—a period that seems unlikely for individual lines under natural conditions. As for the very fact of transplantation to less suitable and completely unsuitable plants, it is not unusual. In nature, aphids often find themselves in such a position: either a winged female is carried by wind into an unsuitable biotope, or rain or wind drops a wingless aphid onto another plant. Only in nature, unlike in the laboratory, the insect usually dies when out of place. We rarely think, when speaking of harsh, catastrophic, and similar conditions, that equilibrium population density corresponds to values at which mortality balances the reproductive potential of the population. This means that, on average, only one daughter from all the offspring of each female succeeds in leaving her own offspring (“Beckett’s law”: A. N. Beckett, 1860; a year earlier, for example, Ch. Darwin wrote about the same, 1991: 69). Therefore, elimination in populations under normal conditions (except for short and more or less mutually balancing episodes of population fluctuations) turns out to be practically equal to fecundity, i.e., close to the maximum. But if almost complete elimination of offspring is the norm of population existence, if the chances of leaving offspring for each individual are always minimal, if the extinction of entire populations is a common phenomenon even in ecological (pre-evolutionary) time scale, then what do we mean by worsening of living conditions? It seems that there is generally no such thing as tightening of conditions at the population level in nature. Even applied to species and supraspecific levels, it is difficult to speak of it. Here, worsening of conditions may mean only the trivial (in evolutionary time scale) extinction of species, the influence of which on evolution will be felt only as liberation of ecological space and, accordingly, mitigation of conditions. But nature abhors a vacuum, and ecological space in particular, and surviving species will instantly fill the void. They will intensify the reproduction process of surviving populations and thereby nullify the short-term mitigation of their living conditions. Thus, evolutionarily significant mitigation of living conditions is as questionable as their tightening. Mitigation of conditions by itself means only increased survivability and, consequently, population growth. At the same time, the Malthusian geometric progression of reproduction will lead to saturation of ecological space and restoration of normal conditions for individuals and populations, including normal (balanced with fecundity, i.e., almost 100%) mortality, within a few generations. Changes in population characteristics as a result of density fluctuations (“life waves”), as is known, are limited only by changes within the range of normal intraspecific variability. The fact that population density fluctuation is the most common phenomenon, and yet no cases of irreversible evolutionary change caused by it have been described so far, proves that this phenomenon is not significant for evolution. So, neither mitigation nor tightening of living conditions represent real factors of evolution. What, then, can overcome the stability of a balanced epigenotype and successfully lead the organization of a living being beyond the historically established norm? The reason for the stability of a balanced epigenotype lies in a compromise once achieved between contradictory needs for optimizing different adaptive functions of the organism. These needs are contradictory in the sense that, due to the complex interweaving of morphogenetic and functional connections between all parts and characters of the organism, adaptive enhancement of one function entails losses in the efficiency of others. Weakening the integrity of ontogenesis, facilitating independent transformations of individual systems, is of course possible and occurs in nature. However, this direction (simplification of organization and general degeneration) is sufficiently specific, requires special conditions, and is neither characteristic nor particularly widespread. After all, to lose organizational height, one must first acquire it. The weakening of integrity as a mechanism of evolution exists, but it is clearly insufficient to explain the evolutionary process. Thus, we need to reconstruct conditions under which organizational change occurs under conditions of preserved or increasing integrity, or rather, when temporary reduction of integrity is quickly compensated. To do this, let us try to refine the metaphor of adaptive compromise. The main problem for evolution, as we have seen, is the contradictory nature of relations between adaptive functions in the process of their optimization. Contradiction arises, on the one hand, from the close ontogenetic and functional connections between systems ensuring these functions, and on the other—from strict control over proper performance of all these functions. We have seen that weakening of connections is possible but insufficient to explain evolution. General weakening of selective control over proper performance of adaptive functions, as we have seen, is also impossible: in evolutionary time scale, elimination is always close to the maximum possible values. Where is the way out? A hint here is provided by the discussed situations that provoke rapid evolution. What they have in common is the population’s entry into new, unusual conditions. The clearest experiments with aphids show what exactly is unusual about the new conditions. There, the experimenter presented aphids with very strict requirements along one or a few parameters (in this case—the ability to feed on an unsuitable plant), but at the same time freed them from strict environmental control along other parameters: protected them from bad weather, predators, parasites, diseases, etc. I am not aware of studies analyzing such a distribution of selective control intensity among first settlers on islands or in new ecological niches. However, general considerations regarding the lower intensity of competitive relations in island conditions compared to mainland ones are quite plausible. They are confirmed by the relatively high immigration potential of mainland species to islands and extremely low in the opposite direction. In such conditions, cenotic control over the performance of some functions (for example, the function of protection against predators and specialized parasites, which are often deficient in island communities) may be reduced in favor of strengthening control along other directions. After all, the conditions are new precisely so that the distribution of selective requirements there is different from the previous one, and in particular, some functions are controlled much more strictly than in previous conditions. If the population survived under these conditions, it means that total elimination did not stably exceed its reproductive potential and, consequently, selective control of other functions was reduced. Thus, evolution is apparently provoked only by unilateral mitigation of environmental control, under which only some of the adaptive functions remain under strict observation by selection. An obvious consequence of such unilateral (unbalanced) control is disruption, destabilization of the established organization, and it indeed manifests itself in such cases (Zerikhin in: Activity..., 1967; Belyaev, 1974; Shishkin, 1984, 1987; McSippe, 1990, etc.). Since adaptability inevitably decreases during destabilization, reorganization can hardly occur under normal conditions. It follows, incidentally, that an emerging group is unlikely to invade an already occupied niche and displace its owner. It is more plausible that it will occupy a niche freed by the extinction of its former inhabitant, or will be able to create (open) a new niche. Perhaps this is why we know quite a few plausible examples of recent emergence of new taxa in island conditions, as well as during anthropogenic introductions. Particularly striking are helminthological examples (cited in the discussion of Rausch’s report, 1982: 184) of two consecutive acts of speciation within 300 years (in a parasite of the house mouse introduced into North America) and divergence of two species of human tapeworms no more than 16 thousand years ago. Around us, there are very few such examples, although under normal conditions both biodiversity and the degree of its study are much higher, and accordingly, the probability of detecting cases of natural speciation is higher. What has been said allows us to suggest that evolution at the species level and especially at higher taxonomic levels is possible only as a result of such a change in conditions under which selection acting on the population becomes substantially unilateral. Only such selection seems capable of overcoming the stability of the previous well-balanced adaptive compromise. However, a newly emerged group that has undergone destabilization and lost its former balance must undergo strict comprehensive control (selection for all adaptive functions) and, under its influence, restore its stability. In other words, evolutionary change must pass through two stages—destabilization and then stabilization of the newly balanced epigenotype. As already mentioned, the results of these events can be identified respectively with inadaptive and euvadaptive changes in organization. In other words, in the process of evolution, the organization of living beings passes through three consecutive stages: inadaptation, euvadaptation, and stasis. Unless, of course, extinction occurs, which is possible at any stage, although the most risky in this regard is naturally the process of euvadaptation, and the calmest is stasis. The first two stages, as the most vulnerable by necessity, must be short-term, while stasis can continue indefinitely. Exit from stasis is unlikely to be spontaneous: the cause must be a change in conditions. If such a change causes an increase in total elimination beyond reproductive potential, extinction of the population (and of the species if all its populations become extinct, and of the higher taxon if the same happens to all its species) is inevitable. If, however, living conditions change in such a way that control over the organization becomes unilateral, it is possible that the population will enter the process of inadaptive transformation of its balanced epigenotype. And whether it will be able to successfully pass through it, and moreover—the extremely risky process of euvadaptation, is a matter of chance, and a very rare one at that. Here it is necessary to note another important feature of our model—its self-regulation.{ "translation": "No matter how high the stability (preservation) of the epigenotype of even a substantial portion of the inhabitants of our planet might rise, cataclysms are unlikely to seriously threaten the diversity of life on Earth if, of course, evolutionarily significant spans of time are considered. Even if a substantial portion of biodiversity were to “ossify” perfectly and, consequently, become substantially “thinned out” by a subsequent catastrophe (a subglobal glaciation, an asteroid or nuclear winter, or a similar apocalypse), nothing terrible would happen to the biosphere. The surviving species would find themselves in situations of incomplete communities with significantly weakened competitive relations. This would provoke rapid inadaptive evolution, and even more rapid the more extensive the “thinning” had been. As communities fill, many of those who drew a winning ticket would lose it, but the greater the share of losers, the greater the chances for those who can hold out a little longer. A holy place will not remain empty; it will be filled. True, the new communities might turn out to be little like the former ones.\n\nAs is known, even near the Permian–Triassic boundary, extinction was, although large-scale, not overwhelming: it is usually said that from the middle of the Upper Permian, about half of all families and three-quarters of genera in the seas were lost, and significantly less on land (Fig. 5). Nevertheless, the world, having recovered by approximately the middle of the Triassic, turned out to be very substantially different, and not only in composition but also in trends. The total diversity attained in the seas by the second half of the Ordovician and then up to the middle of the Upper Permian (200million years, i.e., slightly less than the Mesozoic and Cenozoic together!) did not grow but merely fluctuated around the Late Ordovician level. After the Permian–Triassic crisis, growth resumed and continues to this day, having already repeatedly exceeded the Late Paleozoic level of stabilization (Fig. 5). Obviously, the very structure of marine communities changed radically, making room for much greater growth of biodiversity.\n\n[IMG_5]\nFig. 5. Changes in the diversity of marine [and terrestrial] organisms in the Phanerozoic: orders (1), families (2), and genera (3) of marine animals (N/NR — ratio of the number of corresponding taxa at the lower boundary of the century to the number of modern taxa known in the Recent state) (after Alekseev et al., 2001).\n\nAnother important feature of our model of evolution is the relatively low predictability of the results of its action (the very imperfect correspondence between the conditions of evolutionary processes and their results), which is due to the great complexity of the evolving system and, accordingly, the impossibility of simple, predictable solutions. This is, of course, a disappointing property of the model, but it reflects reality (unlike the synthetic theory, from which predictability of evolution follows but is not observed).\n\nThe approach to adaptation as a compromise allows one to align with the selectionist paradigm (“evolution is the process of interaction of selection with the available organization, i.e., with the product of selection of previous generations”) yet another important pattern of evolution not derived from the synthetic theory in general form. I refer to the unevenness of the evolutionary process, so irrefutably following from paleontological data. The three-stage cycle “inadaptation–evadaptation–stasis,” with two very rapidly proceeding initial stages and a long period of evolutionary stability, easily finds parallels with models proposed by paleontologists (Simpson, 1948; Eldredge, Gould, 1972; Stanley, 1975; Gould, Eldredge, 1977) and geneticists (Carson, 1975) in order to introduce unevenness into the synthetic theory. This similarity is unquestionable, but it should not be overestimated. Only the phenomenology is similar, whereas the presumed mechanisms of unevenness in different models differ, including in their realism.\n\nA special place is occupied by the hypothesis of cenotic regulation of the evolutionary process (Krasilov, 1969; Zerikhin, Rasnitsyn, 1980; Zerikhin, 1987; E. Schwartz, 2004). This hypothesis, also based on the synthetic theory and on the easy pliability of the organization of living beings to evolutionary pressure, introduces unevenness into evolution by postulating the rigidity of community organization, which limits the freedom of change in organisms. In its completed form, as presented by E. Schwartz (2004), the logical scheme of the hypothesis of cenotic regulation of evolution can be formulated as follows. Trophic chains in a normal community are strained (available energy is used more or less completely) as a result of evolutionary mutual “fitting” of organisms (coevolution), so that “all places are occupied,” and there is nowhere to evolve except to continue fitting slowly (coherent evolution according to Krasilov, 1969). Disturbances of the cenotic structure provoke evolution, which either quickly subsides or, rarely, passes into avalanche-like incoherent evolution, interpreted as a biocenotic crisis.\n\nThe model described corresponds better to observed processes than those based solely on the discreteness of the biological species (see above), but it too is far from perfect. There is no room here to discuss the hypothesis of cenotic regulation in detail. I will only draw attention to certain inconsistencies. If trophic networks are everywhere strained and “all places are occupied,” why on land (but not in water) does such a large share of green production steadily go directly to reducers, bypassing consumers? (the famous question of Van Valen, “Why is the world green?”; Van Valen, 1971). If disturbances, especially those as large-scale as anthropogenic ones, continue for millennia, and the rate of evolution with cenotic constraints removed should approach its maximum values (the species in Shaposhnikov’s experiments and in Hawaii during the first century, see above, evolved within a countable number of generations), then why is the emerging cenotic vacuum filled by migrants from other countries or cenoses rather than by newly arisen species? And why are there still no ominous signs of the incoherent evolution catastrophe predicted by Zerikhin (Rodendorf, Zerikhin, 1974)? After all, the epigenetical approach offers a more plausible picture of the evolutionary process than the synthetic one—even in its biocenotic interpretation.\n\nThe above does not mean that adherents of the synthetic theory never appealed to the idea of the stability of a balanced epigenotype. E. Mayr (1974; see above) and other authors (e.g., Van Valen, 1982; Laurin, Bruno, 1988) wrote precisely about this. The problem is that this idea comes from a completely different, non-synthetic-evolutionary paradigm.\n\n1.1.2.3. Problems\nThus, it can be concluded that many observed features of the evolutionary process are in good agreement with the predictions of the epigenetical theory of evolution and, in particular, with the metaphor of the adaptive compromise. However, problems remain. The riddle of the distribution of evolutionary rates, so obviously opposite to the predictions of the synthetic theory, still eludes flawless explanation even with the help of the epigenetical theory, although it is not in such irreconcilable contradiction with it.\n\nIndeed, the available data directly contradict the concept of the adaptive compromise, at least at first glance. If we consider the compromise nature of adaptation, in particular the difficulty of changing a well-balanced epigenotype, to be the main factor restraining evolution, then with the complication of the evolving system and, consequently, with the tightening of the compromise, one would expect this restraint to strengthen. In reality, however, as we have seen, evolution of more complex forms of life proceeds on the whole faster.\n\nNot everything, however, is so simple. First, the increased difficulty of changing higher organisms, predicted by the concept of the adaptive compromise, means a lower frequency of adaptive changes in them, but says nothing about other factors determining the rate of evolution. Higher organisms are characterized by directedness of evolution, a kind of orthogenetic factor that increases the cumulative effect of a series of successive changes. Indeed, with the undirected, chaotic character of external changes favoring Brownian evolution, a random return of conditions to a state close to that previously existing will be perceived as such by organisms that have changed only superficially and not deeply. A system transformed more deeply and integrally will subjectively perceive a return to an objectively previous situation as a new change requiring new adaptations. As a result, the evolution of higher forms will include a smaller Brownian component and, accordingly, a larger volume of accumulated changes (Alberch, 1980; Rachootin, Thomson, 1981; Oster, Alberch, 1982).\n\nHigher organisms also possess more limited mechanisms of population stability. Of course, individual stability is higher in them: in accordance with “Bekhterev’s law,” it is the higher the lower the characteristic rate of reproduction (fecundity and duration of generation) of the group, and the reduction of this rate with increasing level of organization is quite obvious. However, the autonomy from the environment attained along this path is, first, oriented toward an evolutionarily mastered environment and is not necessarily good under other conditions. Second, autonomy is energetically costly, since it requires a finer and faster assessment of the state of the environment, without which anticipatory reactions to unfavorable changes are impossible. As S.A. Severtsov wrote, “a stoat, which needs to catch prey equal to half its weight per day for satiation, and a viper, which spends half a year in torpor and is satisfied with two or three voles per week during the summer period, present a good example of the difference in vital energy. Crocodiles in a zoological garden were satisfied with 36g of meat per day. Panthers and leopards, close to them in weight, are given 3.5–4kg of meat per day” (1941: 288). Here, dependence on the environment does not so much decrease as change, so that individual stability by no means guarantees evolutionary stability.\n\nMore important in this context are mechanisms of population stability, above all excess (reserve) population density, which increases mortality and/or decreases fecundity through factors dependent on population density (Van Valen, 1976). Population stability is universal, since a reduction in excess density compensates equally for a reduction in survival regardless of the causes of this reduction. However, the volume of excess density is limited, since it cannot be sustainably raised beyond the carrying capacity of the resource space, and the “triggering” of excess density also has a lower limit, beyond which survival of a sparse population becomes problematic.\n\nThere are certain grounds to believe that a negative correlation exists between the volume of excess population density and the level of organization. Indeed, the volume of excess density is ultimately determined by the position of the thresholds of stable density—the lower, beyond which a population goes extinct due to weakness of the interaction necessary for survival among individuals, and the upper, exceeding which is impossible due to limited resources. The upper threshold of stable density is ultimately determined by the magnitude of the energy flow available to the population that it can use to ensure its existence. With a constant flow, the upper threshold of stable density depends on the energy requirements of an individual (I speak of individuals, not biomass, since the factors discussed below affecting the lower threshold of stable density depend precisely on the density of individuals). Energy requirements, however, grow rapidly with increasing organization, first, due to the generally larger sizes of higher organisms, and second, due to additional costs for auto- nomization, about which has already been said. Therefore, with increasing level of organization, there is rapid growth in energy costs per individual and, accordingly, a decrease in the upper threshold of stable population density.\n\nThe lower threshold of stable density is determined by various factors. It arises or increases with the appearance of sexual reproduction, which for successful reproduction requires a meeting of two individuals, and not just any two. A similar effect is given by adaptations for conditioning the environment (changes in its activity by a group of individuals in a direction favorable for the group). The first factor is obvious, though not rigidly linked to the height of organization (parthenogenesis and asexual reproduction are common even in moderately advanced groups). For the second mechanism, such a connection is not obvious, but is permissible, since high organization favors the development of more effective forms of interaction. Therefore, it can be concluded that with increasing organization, the upper threshold of stable population density decreases strongly, while the lower one increases somewhat, reducing the volume of excess population density and its evolutionary stability. This cannot but increase the rate of evolution of higher groups of organisms.\n\nThe stability of a population and species under changing conditions also depends to a large extent on how capable organisms are of finding slightly changed refuges and shelters in a new environment and holding out in them. This is, of course, largely determined by the dispersal abilities of organisms, which are unlikely to be very closely linked to the level of organization. But there are other, more promising factors in this context. A special role is played by absolute sizes: where small forms can find slightly changed microbiotopes for themselves, large ones often find themselves forced to change or perish. Thus, the age of the Pleistocene fauna (fauna composed half of extinct taxa and half of those surviving to the present) for large and small mammals differs by a factor of 2.5 (200thousand years for elephants and ungulates versus 500thousand years for rodents, insectivores, and bats, Rasnitsyn, 1987, Table1), and these dates fall on the extremely changeable conditions of the Pleistocene. For insects, the Pleistocene fauna is dated to approximately 5million years according to the same data.\n\nAs is known, most large mammals from the peculiar fauna of the extinct tundra-steppe landscape that occupied vast areas of northern Eurasia in the Quaternary died out at the beginning of the Holocene, while small mammals survived in the main (Sher, 1997a,b; Zhegallo et al., 2001). Insects, meanwhile, proved stable throughout the glacial period and postglacial time: according to data of V.I. Nazarov (1984), of 2000 insect species known for the Quaternary period, no more than 30 are considered extinct. Of 731 species recorded in the database for the Anthropogene of the Northeast Siberia (Sher et al., 2006), only 6–8 species are considered extinct with more or less confidence. Moreover, a significant share of characteristic tundra-steppe insect species of the Late Pleistocene has been preserved not only in the steppes of Southern Siberia and Mongolia, but also in places of their former habitation—on small relic “steppe” sites in Yakutia and even on Chukotka (Berman, 2001).\n\nSizes are definitely, though not rigidly, linked to the height of organization: small sizes limit the possibility of complication, while large ones require some minimum complexity at least for life support and coordination of actions of remote parts of the organism. Therefore, the availability of stable refuges under changed conditions, lower for higher forms of life, should noticeably reduce their evolutionary stability and increase the rate of extinction and evolutionary transformations.\n\nThe factors listed above hardly exhaust all the diversity of connections between the height of organization and stability that determine the rates of evolution, but other mechanisms are not yet so obvious. Thus, we have managed to discover one mechanism which, if the concept of the adaptive compromise is correct, should reduce the rates of evolution of higher forms of life. This is the compromise nature of adaptations as such, i.e., the difficulty of changing a more complex balanced system. In the opposite direction act more diverse forces. Among them are the more pronounced directedness of evolution of higher organisms, their lower evolutionary stability due to the convergence of thresholds of stable density of their populations, and lower availability of “stability islands” for them, preserved during a general change in conditions.\n\n***\n\nConcluding the section on the ontology of the evolutionary process, it can be said that the epigenetical theory of evolution is in good agreement not only with the results of observations and experiments in the field of realization and transformation of ontogenesis, but also with paleontological data on the evolution of organisms.\n\nA fairly large array of factual data in both areas has become amenable to confident interpretation, and this inspires hope that the remaining problems and questions will be successfully resolved over time.\n\nA.P.Rasnitsyn. Theoretical foundations of evolutionary biology // V.V.Zerikhin, A.G.Ponomarenko, A.P.Rasnitsyn. Introduction to paleoentomology. Moscow: KMK. 2008. 371pp.\n1.1. THE PROCESS OF EVOLUTION\n1.1.1. THE SYNTHETIC THEORY OF EVOLUTION\n\n1.1.2. THE EPIGENETICAL THEORY OF EVOLUTION\n1.1.2.1. Basic tenets\n1.1.2.2. Adaptive compromise\n1.1.2.3. Problems\n\n\n\n\n\n \n\t\t1.2. METHODOLOGY OF PHYLOGENETICS, TAXONOMY AND NOMENCLATURE\n1.2.1. PHYLOGENETICS \n\t\t\t1.2.1.1. Analysis of groups\n\t\t\t1.2.1.2. Analysis of characters \n1.2.1.2.1. Analysis of differences\n1.2.1.2.2. Analysis of similarity\n1.2.1.3. Computer cladistics

1.2. METHODOLOGY OF PHYLOGENETICS, TAXONOMY, AND NOMENCLATURE 1.2.1. PHYLOGENETICS 1.2.1.1. Group Analysis 1.2.1.2. Trait Analysis 1.2.1.2.1. Difference Analysis 1.2.1.2.2. Similarity Analysis 1.2.1.3. Computer Cladistics