Conception of species and reflection of the eudological situation
The principal theoretical problem of critical monographic floristic revision is a problem of basic taxon. In practical systematics where a geographic-morphological (more precisely, ecologically-geographic-morphological) method prevails the species is a basic taxon. The geographic-morphological method of S. I. Korzhinsky and R. Wettstain in V. L. Komarov’s interpretation is namely an ecologically-geographic-morphological method. Komarov’s conception of a species is expounded in more detail in his “Conception of plant species” (1940–1941). It is often forgotten that this work presents a complex of principal theses although given in different parts of the book but showing Komarov’s approach to a problem of species only in total.
These theses are: 1) “Species which are visible at the moment do really exist” (K. A. Timiryazev). … “Species is an objective fact”. 2) Every species takes it’s “place in the economy of nature” (Ch. Darwin). 3) “Species are neither equal in volume nor in extent”. 4) “Species is a totality of generations originating from a single ancestor”. 5) “Species is a morphological system multiplied by geographical certainty … Everyone is aware, however, that within a natural habitat a species occupies far from all the territory … Fixing a position of an organism in nature we ought to keep in view not only distribution but also ecotope and the surroundings of each plant. This is what I call a certainty”. 6) The mainstream in comprehensive systematics makes it’s aim to achieve systematic establishment of monotypic species … Heterotypic species are divided into a corresponding number of new more homogenous species”. 7) “Species … is a system of biochemical balances passing inherently from generation to generation, and every change in this system results in the phenomenon of variability”. 8) At the same time, species is a definite stage of evolution” (Komarov, 1940).
But it is incorrect to consider a species as the only real evolvable natural unit as concieved by Komarov. By no means! First of all, Komarov himself emphasizes more than once, that evolutional place of species can be determined only in series of closely related species (these evolutional series are the basis of all systems, especially if these species are “small”, i. e. accepted in the narrow sense, monotypically). Komarov especially stresses this basis by comparison with another taxonomic category – subgenus: series is a phylogenetic concept, whereas subgenus – morphological. Moreover, “under subsequent isolation” a subgenus can be transferred into the rank of a genus (i. e. genus is also a morphological concept). On the other hand, being a staunch supporter of Darwinism, Komarov does not define what a genus is and refers sympathetically to Ch. Darwin: “Ch. Darwin did not give us a definition of what a genus is, but it is evident from his theory of convergence that if a species presents evolved variety, then a genus is a subsequent stage of convergence, as it were, a divided species”. And, then: “Conception of genus-species gives us an opportunity to restore a picture of life of species in the past and nowadays, while isolated study of species doesn’t”. Moreover, Komarov writes: “So-called taxonomic units, i. e. species, genera, families and classes are not just a method of classification for us but reality, namely stages passed by organisms on their historical path”. He notices that it would be good to make sure that families correspond to a stage of Cretaceous, genera – Eocene period, and species – partly Miocene, partly – Quaternary periods, whereas subspecies and variety – comprehensive. But “actually a process of species forming takes place in a more complicated manner!!”. And then: “a value of deviation is a false criteria for us, it is principally that … a place in the economy of nature belongs to every real species”. Undoubtedly, taxonomic hierarchy is a true reflection of evolutionary stages for Komarov, but he builds his ideas around the system of organisms “bottom-up” (beginning from a species) and, moreover, he is a staunch supporter of monophyly (as according to Darwin). Therefore, in his conception genera and families had no more than only one ancestor (single species), but we are not aware of these ancestral species and reflect for this reason real (recent) history in evolutionary series, but earlier stages of the history of organisms – in taxonomic hierarchy. “The whole system is nothing but a reconstruction of a genealogy”.
However, to understand this system of ideas denoted in Russian-language literature as “Komarov’s conception of a species” – in Komarov’s statement, but not of his interpreters’ (S. V. Yuzepchuk, M. V. Klokov, A. K. Skvortzov) – it is necessary to focus on two components of this conception. First of all, Komarov, writing about a monotypy of species, admitted it is possible to distinguish intraspecific units. Several chapters of his work were specially devoted to different types of intraspecific units; he considered a whole series of these units (clones, pure lines, inbreeding lines, etc.) as a phylogenetic phenomena which, under specific conditions, turn into peculiar species. He wrote also that “in a structure of species it is possible to recognize geographical and ecological races as a new speciation”. Occasionally he names these races “subspecies”. This term was often used by S. I. Korzhinsky (1892) for marking geographical races, which are not completely isolated from each other, or have intermediate morphological forms within area of distribution of both subspecies, already isolated at the present time. Komarov considered S. I. Korzhinsky’s work perfect in the methodical aspect and appointed Korzhinsky his predecessor. But in a strange way he had misunderstood what Korzhinsky meant dividing in characteristics of species features of morpfome and biont – it follows from remark “bionts remind very much biotypes”. However, Komarov constantly treats Korzhinsky’s subspecies as small species forming a series.
Secondly, Komarov, who kept an attentivel eye on achievements in genetics, focuses several chapters of his main book on phenomena of hybridization, apomixis, mutations and role of polyploids in race forming. Major ideas necessary for understanding Komarov’s position are the following. 1. “In many cases, varieties and forms turn out to be an evident chromosomal mutations, which appearance can be explained casually”. 2. “Variability becomes apparent where there is (are) a partner(s) for hybridization. Hybridization sets a revolutionary way a nature of species and results in the appearance of new forms, existing at least a short period of time”. 3. “… Species has an importance as a uniform population having a certain position in the econony of nature, independent of the path of its’ origin. We have to distinguish species of hybrid origination and hybrids; the first one is characterizing, by the way, by more high fertility, ability to keep up its’ unity independently of new crossings and to live its’ own life independently of parents species”. 4. “In general we have to accept here three different phenomena. 1) individuals present direct offspring by the crossing of two different plants; 2) probable offspring of these hybrids; 3) hybridogenous species asserting certain position in the economy of nature in a definite area and keeping their characteristics even when crossing with other species to the same degree as a non-hybridogenous species”. 5. “Hybridization in those cases where it was proved [Alchemilla species – R. K.] lead to obligatory apogamy (more precisely, ovoapogamy), which brings to mind that the ovoapogamy in this systematic group has generally appeared through hybridization” [Komarov refers here to the works of Murbeck and Buser who showed that some Alchemilla species produce normal pollen, and pollination, fertilization, and also reducing division are present – R. K.]. 6. “Such a microspecies as the Alchemilla species are so original that we have to recognize them as a special type. Common species are amphimictic, whereas these are apomictic”. 7. “In this group of Corydalis three related species occur together, and, although having defferent periods of flowering, in some cases are capable of cross-pollination … their diversity is easily explicable by crossing at first between species, then – also between hybrids … we deal again with a hybrid cycle”. 8. “Hybrid cycles as some kind of dissonance rush into the general order of nature living usually in species … If hybridogenous species is a real species then hybrid cycles and apogamy are not evident”. The destinies of species, hybrid cycle, and apogamic race are not the same. The latter do not have such a complicated history as a species. These groups are interspecific and their existance is more fleeting …”. “Hybrids and hybrid cycles are not species, they present only a kind of formation parallel to a species, as well as their agamic offspring, only if separate hybridogenous individuals are not subject to the peculiar conditions favourable for their reproduction and form a hybridogenous species. The latter present once again a totality of generations which originate from a single ancestor”.
The above presents V. L. Komarov’s conception of a species. Also, it is important that Komarov constantly emphasizes the complexity of natural processes (“it is inacceptable to fit everything we see in nature to the same dimension”).
Having writing his main book in 1938, Komarov himself stressed that knowledge of the nature of a species and their evolution had grown considerably in comparison to the beginning of the 20th century. In fact, Komarov employs many of the world’s botanic and genetic achievements (he accurately refers to these papers). But it is clear that he also knows and uses data obtained by Russian science, especially of soviet botanists-systematics, although he does non cite them, although the works of N. I. Vavilov’s colleagues are cited. Thus, he interprets S. V. Yuzepchuk’s works on Alchemilla and Anemone (having correced the author in this case, as well as in the “Flora of USSR”). It is clear enough, that Komarov also read his work on Cousinia, in which Yuzepchuk describes a phenomenon of “gregarism”. But this term, originated from “non-formal taxon – grex” and has been used since 1920s by M. G. Popov, Komarov prefers to replace by “hybride cycle”, although he points out, that in different situations he places a different meaning on this. In some places Komarov also employs Ya. Lotsy’s term “syngameon” (totality of individuals crossing in either combinations). G. Turesson’s conception of ecotypes (and its modifications in works of N. I. Vavilov’s colleagues) was also well assimilated by Komarov. Using some examples, he demonstrates that it is impossible to classify ecotypes as a special intraspecific taxa, but emphasizes that in some cases, when the ecotypes are isolated enough, it is possible to equate them with a “microspecies” (ecological races). He gives some examples of such an “ecological species”, including the species of “Cretaceous flora” of south European Russia.
At the present time, 65 years after Komarov’s book was published, we, definitely, know much more about plans and their evolution. Moreover, this greater knowledge, in contrast with V. L. Komarov’s ideas, tried to summarize S. V. Yuzepchuk (25 years after the main book of V. L.) and A. K. Skvortzov (35 years after). It is interesting that these authors, both being a highly experienced systematists, worked with exceptionally complicated objects, erudite scientists, well informed about achievements of modern to them genetics and selection, and, at the same time, experts in classical botanical literature, by paradoxical way hadn’t noticed that essential new that Komarov sayed in his main book, in contrast with his earlier works. They spare main attention namely to the earlier ideas of him. And if in this case it is quite understandable, why S. V. Yuzepchuk in his main work (Yuzepchuk, 1958) do so, then for understanding of A. K. Skvortzov’s position, stated in his work “V. L. Komarov and conception of a species” (1972), it is necessary to address to other work of Skvortzov concerning this subjects. S. V. Yuzepchuk, stressing himself that he is one of the first Komarov’s disciples, certainly absolutely deliberately addressed to the history, having denoted most of his work to the proof of originality of “Komarov’s conception of a species” in the form accepted in “Flora of USSR” (i.e. earlier, than the Komarov’s main work appeared), and also, in some measure, priority of V. L. Komarov as one of the founders of a geographic-morphological method in systematics (Yuzepchuk, 1958). The most important in Komarov’s conception for S. V. Yuzepchuk is an understanding of a species as an integral biological and evolutionary unit, reality of a race-species as a totality of connected by common tribal life and occupying determined place in the economy of nature individuals, and, finally, statement in this new synthesis of a species monotypy. Absolutely clearly that in some measure a task of this Yuzepchuk’s work is a revision of own views on the history of development of a geographic-morphological method of systematics, stated in his earleir work “Problem of a species in the light of Darwinism” (1939), published in the form of a discussion in quite another way.
In this work Yuzepchuk also discusses a problem of hybridiztion of plants in connection with speciation, in which he was always interested (including phenomena, named by himself a “peripheral (marginal) hybridogenesis” and “gregarism”), proving that an admission of a certain role of hybridization in the process of speciation “does not contradict with Darwin’s theory”. It was exceptionally important, because the same phenomena were used also by A. Kerner, studied well enough hybridization in nature and advanced his own theory of evolution of plants (Vermischungstheorie), in which Darwin’s “struggle for existence” was for the first time renderred concrete from ecological positions through occupation of free niches by constantly forming in result of hybridization new forms, but natural selection sensu Darwin was given no more than a subordinated role. But Yuzepchuk does not discuss in his work (1958) Komarov’s views on the role of hybridization and different destiny of hybrids, hybrid cycles and hybridogenous species at length. Another part of Yuzepchuk’s work is devoted to the “reflection of Komarov’s conception in “Flora of USSR”” and is a review of critical statements on taxonomic decisions, taken whilst compilling the “Flora of USSR”, based on a concept of a species elaborated in V. L. Komarov’s papers.
A. K. Skvortzov (1972) has delivered with his work on Komarov’s conception of plant species after his fundamental monographic work on willows of USSR was completed and some interesting, but highly contradictory papers on history of conception of a species and essence of a taxon development were published. As Yuzepchuk, Skvortzov tried first of all to demonstrate the evolution of Komarov’s ideas concerning a species, beginning with his early works, but only to a small degree Skvortzov took into account that total of V. L. Komarov’s ideas, presented in “Conception of plant species”. Having appreciated correctly the important part of Komarov’s work, in which he defines a race (species) as a unit of tribal life, Skvortzov at the same time for some reason states that V. L. Komarov in “Conception of plant species” changed his former positions in respect to the geographical certainty of species (races). Skvortzov also reproaches Komarov for being inattentive regarding the problems of intraspecific variability, but these reproaches are unjust. Komarov by no means understood a “monotypy” of a species “as morphological homogeneity”: not without purpose has he devoted a special chapter of the book to clones and pure lines, not unintentionally does Darwin’s thesis “variety is an initiated species” run throughout the book. Skvortzov understands well the importance of this new step in development of Komarov’s ideas, that biological nonequivalence of species is not only proclaimed as a rule, but also illustrated by examples (moreover, not only of amphimictic and apogamic races, as it is stated by Skvortzov). However, in the same manner as Yuzepchuk, Skvortzov doesn’t see as if point-blank that Komarov in his last work considers, among other things, a role of hybridization, demonstrates a possiblity of hybridogenous speciation, and, above all, emphasizes that in the world of plants specific forms of evolutionary process – “hybrid cycles” which are as if parallel to species, but not species (!), – are present. The first who noticed and appreciated this was V. I. Polyansky (1944). Moreover, the last chapter of Komarov’s book contains a remarkable paragraph which also confirms these Komarov’s thoughts: “It is a great temptation to assume that the process of appearance of a new species, fit to new conditions, runs by the way of well known Hegel’s triad: beginning from primordial uniformity through maximal diversity to final uniformity … Yet, it is probable that this is far from being the only path by which speciation occurs, but is just one of them”.
It is these, Komarov’s thoughts, which lead us to consider him as the herald of eudological ideas – ideas on the variability of natural races (monotypic species, but not only species).
Undoubtedly it was Komarov’s thoughts (and also S. I. Korzhinsky’s ideas) which influenced M. V. Klokov’s theoretical works which dealt with exceptionally complicated groups of thyme (Thymus L.) where, in practice, a series of closely related species are observed which do not replace each other geographically. Yet, in 1947 in his doctoral thesis “Endemism of Ukraine flora”, he proposed to distinguish a special biological discipline – bioeudology, the main aim of which was to be the creation of a theory of biological units as a reflection of various ways of race forming in nature. Unfortunately, this important idea was from the very beginning blamed by the fact that M. V. Klokov (just as S. I. Korzhinsky before him) considered races as natural, comprehensible empirically objects, but, at the same time, treated a species as a formally-logical concept which can be defined as an aggregate of several races or only one (geographically fixed) race. Klokov himself prefers the latter, i. e. distinguishing every natural geographical race and attributing it to an independent species if it is “possible in practice”. In the case where a group of races is presented by offspring and ancestors of different age, it is possible to distinguish “sovidia” – phylogenetic (not taxonomic) categories reflecting real natural series of races. According to Klokov, Komarov’s series is just a useful (but not natural) category. The rational idea of M. V. Klokov’s thoughts (especially in his latest works of 1960, 1973, etc.) is that inequivalence of natural races means not only a degree of their divergence from most closely related races (as S. I. Korzhinsky yet saw) but, first of all, – which path of evolution they reflect (this is exactly the new idea which had been perfectly expressed by V. L. Komarov). This is why the science of races as natural units of evolution – eudology (bioeudology) – is necessary. Evidently, it is imperative, if K. M. Zavadsky (1967) also wrote about it (without reference to M. V. Klokov), having defined eudology as a science of species (and speciation); he distinguished different types of speciation, and introduced (unsuccessfully) a concept of “hemispecies”.
At approximately the same time I also, referring to M. V. Klokov, supposed that the totality of data on objects of populational-species level of organization of living substance, presented by different special biological disciplines, is the object of science of natural races (species) – bioeudology (Kamelin, 1969). But both then and later I unfortunately did not succeed in publishing this work (slightly unfinished) devoted to different natural objects of this level of organization of living substance. Meanwhile, the developments in plant genetics, biosystematics, and numerous other special branches of botany confirmed the necessity to develop a theory of different evolving units in the plant world, a theory relating to the diversity of units of plants’ “tribal life”. Their diversity is just immense in the plant world, as well as in the world of mushrooms and in numerous groups of arthropoda, i. e. exactly in that phylums where a number of modern species is especially great.
Elementary units of tribal life of plant organisms, where micro-evolutionary processes run, are clones, pure lines and populations. The diversity of all these units is great enough. Thus, clones can be vegetative, agamic, parthenogenetic (obligatory apomictic), pure lines – at least autogamic (homozygous) and pseudohybridous (matroclinous), populations are mostly diverse. First of all, normal monospecies populations of freely crossing individuals are divided on properly panmictic (syngameons in the sense of Ya. Lotsy), isogenous (with family type of differentiation or with considerable part of self-fertilization or geitonogamy), and exogamous (with considerable occurance of self-sterility). Secondly, in the plant world, the role of hybrid populations of different types – classical two-species (and two- and subspecies) and mixed (introgressive-interspecies) – is considerable. Moreover, in different types of populations variants of combinations of individuals occur with unequal ploidy (different cytotypes) either with a high degree of isolation, completely or partly crossing.
It is clear enough that, in the case of absence of syngenesis agamic and vegetative clones do not form a species (even if the number of individuals is rather great), but agamic organisms are able in result of selection in variegated environment to produce an ecological (and morphophysiological) forms (in the case of coexistence – also agamous complexes of different forms). Obligatory apomictic (parthenogenetic) clones most often are connected with past hybridogenous processes and, probably, in some cases, with changes of environmental conditions they are able to restore, at least partly, a syngenesis (and, therefore, to form a natural species, initially hybridogenous). Unisexual clones also exist which are sometimes capable of producing individuals of the opposite sex and in consequence also similar to an amphimictic species.
Pure lines of obligatory self-fertilizers in the strict sense also cannot be attributed to an independent species (jordanons) still they exist within populations of the same species together with interline hybrids, or with cross-fertilizing lines of the same species. However, in the case of loss of these connections, and taking by proper pure lines of certain niches, these natural races are also in principle comparable with species. Pseudohybrid matroclinous pure lines can also to some degree be compared with species, especially if they have a marked capability of occupying and keeping life space.
Unispecies populations of either type present in nature ecologically-geographical races constituted usually by numerous local populations of different capacity but sometimes – by only single population. It is these natural races we call species if they are separated well enough (isolated biologically, ecologically, and geographically) from related races, or subspecies if isolation is incomplete, even if their geographical distribution is certain. But, in evolutionary aspect, species and subspecies can display absolutely different phenomena; it is understandable only when we study them in respect of eudological units of a higher level of organization – groups of contemporary closely related races (species and subspecies). V. L. Komarov documented in his conception of the species a relation of species (natural race) to another relative species in an evolutional series (contemporary species!) as a principal link in the evaluation of evolutionary phenomena. As I pointed out above, this outstanding achievement of V. L. Komarov’s phylogenetical systematics was misconstructed by the incorrect application of it in the logical classification of organisms (Kamelin, 1973). V. L. Komarov himself had formulated his method distinctly: “I propose to reject the standard method of division of families, genera, species into minor sub-units, but insist on unification of these minor sub-units, beginning from biotypes, in the evolutionary series, finally forming the same species, genera, and families; not apart from each other but forming distinct comparisons regarding their evolutionary connection” (Komarov, 1941 : 4). It is impossible to understand this opinion ambiguously, but, however, the essence of this opinion was misinterpreted by many of the following investigators. Komarov himself did not give cause for it, the series in his numerous revisions are unequal in their capacity, but they always reflect an idea of the evolutionary connection of the species within a series of other contemporary species. Komarov, however, attached to them a taxonomical significance of elementary units of classification (logical), using, at the same time, such a taxa as sections and subgenera. This is why M. V. Klokov (1961) proposed to reject the use of the term “series” (which is quite useful in taxonomical interpretation); much earlier S. V. Yuzepchuk (1936) paid attention to the fact that in a series based on contemporary species more often we do not deal with the relations of one species to another contemporary species as ancestor and offspring, but with the parallel origin of a closely related species from a common yet extinct ancestor. In actual fact we deal in nature with quite a different relationship of species within closely related groups. Essentially there are series of closely related species, well known to Komarov (for instance, ancestral type of Middle Asian poplar – Populus talassica Kom., called by Komarov mostly as P. densa Kom., and its direct offspring – Pamirian poplar P. pamirica Kom.). It’s quite another matter, that in this case an interpretation of Pamirian poplar as a subspecies is also possible. But, of course, in nature we often deal with bunchs of closely related species (or subspecies), developed within an area of distribution of their common ancestor, which is now extinct. This type of relationship reflects a term, proposed by Yuzepchuk – “fascis”. These evolutionary relationships are very typical for some polymorphic groups of Astragalus, whose degree of isolation can differ, and just such a bunchs of species can contain not only species, but also species and subspecies. However, in the same groups of the genus series can also be discerned. Vastly separated species also present considerable complication for taxonomic expression of evolutionary relationships race (species) – series, or members of presently reduced series, or latest “saltatory species” (strongly isolated). M. G. Popov in his early works gave an example of such a species – Astragalus thlaspi Lipsky (then it was distinguished as a representative of a monotypic section or even as a distinct genus, but in actual fact it is just a “saltatory species”, in general rather close to some other annual species of this genus). In many cases series, or bunchs of closely related contemporary species are complicated by the combination with a distinctly separated species of the same affinity, which are neither ancestors nor offspring of other members of a similar complex of races. Just this situation can be observed in the affinity of Anemone narcissiflora s. l. Undoubtedly, we deal here with a special evolutionary (and eudological) situation, connected neither with hybridogenesis nor with introgression. But, surely, in any case we shouldn’t interpret more isolates species as monotypic (or monotypic only at the present time) series (or “bunchs”).
As is well known, hybridization between different species is rather common evolutionary phenomenon in the world of plants. Hybridization between distinct individuals belonging to different species, or hybridization over rather extensive areas between different populations of two or several races (of different species). The evolutionary consequences of hybridization are extremally varied. Hybrids between individuals belonging to different species can be sterile, but, propagating vegetatively, they are able to produce clones existing for a long time (it is very common in species of Salix, Rosa, etc.). In other cases, hybrids can cross with individuals of one of the parental species and, in this way, be absorbed in reciprocal crosses, enriching the population of one of the parental species by some new characteristics (and forms). More rarely, hybrid forms obtained as a result of heterosis, possess a higher fertility, and, in some cases, have more developed pollen, and in the process of reciprocal crosses with one of the parental species are able to absorb this parental species. Such a hybridogenous population can in time turn into a hybridogenous species isolated enough from other parental species. Many of the hybridogenous species in the genus Potentilla, for instance, P. approximata, P. agrimonioides, have such an origin. Isolation from the parental species in this case is connected with polyploidy, with producing hybrid individuals as a result of crossing with parental forms in connetion with a higher level of ploidy of hybrids (tetraploid, hexaploid). Regarding their high fertility, formed hybrid races are able to occupy spacious areas, and are capable of replacing almost completely the parental species. These races do not differ in any way from those which appeared in accordance with the classic divergent scheme of “Darwin’s evolution”, although the forming of hybridogenous species often takes place more quickly. More often than not, these species appear at the borders of areas of distribution of closely related species, especially if one of them is present at the border of the common area of distribution of this species by differing enough (isolated, semi-isolated) ecologically-geographical race (subspecies). In this case ordinary interpretation of parental species and common field of hybrid populations of these species as a single polymorphic species with several subspecies or as two species, one of which includes subspecies, comprising also all combinations of interspecies hybrids (which is a very typical phenomenon in case of “peripheral hybridogenesis”), from the eudological (evolutionary) point of view is quite inadmissible. In differing cases here it is possible to discern diverse evolutive units, but the number of them is not one, or two, or three – as a rule, it is much higher, and destiny of the each of them, although brief, is quite diverse.
As a rule, in those cases where two different species, poorly separated from each other biologically and rather close ecologically, cross over spacious areas, we are dealing with wide belts, where both parental species and hybrids, and numerous variants of reciprocal crosses exist. It is typical for different cases of “introgressive hybridization”, independently on their reasons. Belts (or “zones”) of introgressive hybridization of higher plants are quite different. At the same time, “race compound” in zones of introgressive hybridization can be exceptionally diverse, especially in those cases when in the wide field of “introgression” hybrid forms already predominate. For example, these widest belts of introgression demonstrate our firs – boreal-nemoral European Picea abies and boreal and boreal-mountainous Asian (partly also North-East-European) P. obovata, larches Larix sibirica and L. gmelinii (L. dahurica), etc. In these belts of introgression, hybrids already predominate (this is why their taxonomic interpretation as hybridogenous races-species is justified). Simultaneously, in the belt of introgression it is not rare to find the appearance of forms closely resembling the parental species (they occur spontaneously within the common area of introgression) as a result of diverse recurring crossings. At different sites within the belt of introgression a compound of hybrid forms can change in its phenotype. At the same time, with the exception of some differentiation of “family”-type, any important isolating barriers in these cases do not exist. Therefore, in the strict sense, they represent not hybridogenous species isolated enough, but introgressive-interspecific complexes of hybrid forms.
It’s quite another matter, if over the same spacious areas introgressive hybridization is accompanied by a switch to apomixis. The main part of these races in these case turn into apomictic clones, and not unfrequently – also vegetative clones. Of those vegetative clones, only a few individuals are capable under special conditions of producing fertile pollen and double fertilization, and can, consequently, produce seeds, from which hybrid forms with other combinations of characteristics develop. These are “cycles of apomictic races with facultative apomixis”, or “hybrid cycles” in the strict sense. A considerable concentration of original apomictic races is rather common in the hybrid cycles of Alchemilla (A. vulgaris sensu lato) in mountainous conditions (Ural, Caucasus, Altai), whereas in the plains (rather spacious) the number of these races is diminished. It is quite logical to propose that conditions favourable for the development of amphimictic forms (and races), producing further new apomictic clones, appear more often in the mountainous regions. Initially hybridogenous origin of all these races in the cycle of A. vulgaris, represented by several hybrid-clonal complexes with facultative apomixis, is confirmed well by data on chromosome numbers of European species. These are polyploids (octaploids, decaploids and higher) with frequent cases of aliquant aneuploid diminution (2n – 64, 90–96, 100–104, ~ 110, 130–152, 148–156).
Another type of hybrid complexes present hybrid-polyploid complexes of races, where normal amphimixis remains, and the number of apomictic forms is low or even just absent. Forming of hybridogenous races and forms is connected here with switch to more high, then tetraploid, level of ploidy. Diploids and tetraploids cross here freely with each other, but cytotypes with more high level of ploidy (hexaploids and higher) are able, seemingly, to cross with races of the same level of ploidy only. Complexes of microspecies in Juncus bufonius s. l., Caltha palustris s. l., in some groups of Achillea present such a type of interaction. As a rule, number of diploid and tetraploid races in these groups is limited, while number of polyploids with more high level of ploidy is hihger, and the latter polyploid races are more homogeneous morphologically.
In many groups of flowering plants hybridogenous species form as a result of crossing of two-three species and further reciprocal crossings at once in considerable number of not only viable enough but more productive, then parental, individuals. Quite often these individuals are very diverse in karyotype or (completely or partly) in the time of flowering. Consequently, one of the parental species (or even all of them) disappears, but in most of the cases one of them remains in a changed form (with a higher level of ploidy). Further development of such hybrid groups leads to the forming of several hybridogenous races separated well enough from each other. This way of racegenesis has been known for a long time. M. G. Popov (1927) called these groups “grex”, and S. V. Yuzepchuk (1932) – phenomenon of “gregarism”.
“Gregarism” is rather common in many genera of Rosaceae (Potentilla, Rosa, Cotoneaster, Crataegus, etc.), Compositae (Cousinia, Cirsium, Chondrilla, Saussurea, etc.), Gramineae (Poa, Festuca, Calamagrostis, etc.), and also in Calligonum, Lappula, Tamarix, Thymus, etc. Gregarious complexes (cycles) of species are very diverse in their display for the reason of different age of them at the present time. Some hybridogenous species in these complexes are narrowly local, others are widely distributed and these very often overlap areas of distribution of related species. Quite different cytotypes are often formed within these complexes (both aliquotly polyploid and aneuploid). Some species of certain genus, capable of hybridization with many other species of the same genus, serve as a parental type. They are very diverse in different genera: in the genus Cousinia, for instance, it is a very stable in morphology biennial species C. microcarpa, in the genus Potentilla, on the contrary, it is an extremelly polymorphic P. argentea. The development of “obligatory unpaired polyploidy” is also highly fruitful in gregarious complexes. It is distinctly expressed in the genus Rosa (numerous races of the section Caninae). One more reason for prolonged development in isolation of separate races in gregarious complexes is aneuploidy, which has been extensively investigated in Crepis and Youngia (Compositae), Cardamine, Lesquerella (Cruciferae), Knautia, Cephalaria (Dipsacaceae), and also in Carex. Moreover, in Carex, Eleocharis, and in some other genera of Cyperaceae, as well as in the genus Luzula (Juncaceae) it also accompanied with agamatoploidy (variability in number of pairs of conjugatihg chromosome fragments of polycentric chromosomes with diffusive centromeras). At the same time, in gregarious complexes in some groups of Veronica, Linum the increase of isolation of hybrid races is connected with aneuploid diminution.
In some cases, when the number of hybrid races which are capable of easy exchange with each other by genetic material as a result of complete compatibility of genomes, is especially high, and areas of distribution of many of these races overlap in spacious territories, where these races, of course, cross, we deal with a special phenomenon – “hybrid swarms”. In the widest sense it is a particular case of development of “syngameons” sensu lato (or “hybrid-syngameos”, in the sense of Du Rietz). The term “syngameon” was coined by Ya. Lotsy, who applied it in his early works to denote the totality of individuals crossing in any combinations, i. e. which was named later a “panmictic population”, but which was also applied to denote what was later named “pure lines” (Lotsy, 1906, 1916). Lotsy treated syngameon as a natural evolutional unit, whereas species is simply a conventional subjective concept (hence he proposed to call them linneons). In his later works, however, Lotsy treated syngameons in a wider sense, considering it possible to define all European birches as a single syngameon. Du Rietz also understood that “hybrid-syngameons” present formations of quite different volume, whose members are connected with each other through hybrid forms in different combinations, not rarely with complete predominance of hybrid forms (Du Rietz, 1930). The most striking examples of these formations, in his opinion, were North-European willows and the New Zealand species of Nothofagus. Genetic investigations confirmed that many groups of flowering plants present syngameons. These being the whole sections of oaks in North America and Europe, the whole genus Aquilegia, subgenera of the genus Polemonium, sections of the genus Iris, polyspecies groups in such a genera as Populus, Salix, Sorbus, Crataegus, etc. But in nature, different syngameons interact in quite a different way. If white oaks in North America present real natural “hybrid swarms”, then the species of the genus Aquilegia, absolutely compatible with each other in culture (and in selection), in nature in some cases give well expressed lines of substituting closely related species, crossing only with more distinct species, which occur in the same territory. Yet another form of syngameons are the formation of compiled species (compilospecies: Harlan and de Wet, 1963). Evidently, the common reed (Phragmites australis) has just such origins.
Outlined above, the eudological diversity of natural evolutionary systems in the world of plants does not exhaust even a part of the real diversity of the evolutional systems of plants (here, for instance, were not yet described numerous yet investigated by geneticists original systems developed in Oenothera or Hieracium, in complex Aegilops-Triticum, etc.). Some of these are described well by V. Grant (1984). As well as many other systematists of plants and geneticists before him, Grant knew well this diversity, but he has made an “original” decision. He was an adherent of “biological species” and wrote therefore: “Our conception of biological species deals only with biparietal organisms. It doesn’t extend to uniparietal organisms which don’t form crossing groups. Meanwhile, uniparietal propagation is very common in plants”. In this connection he discerns species and “non-species”. Non-species are microspecies and semispecies. He equated microspecies with “jordannons” (pure lines), but attributed agamospermic races also to microspecies. He considered the latter term useful for groups of plans with uniparietal propagation. Semispecies are rather common in plants with biparietal propagation races, differing from species by a low degree of reproductive isolation. Semispecies are also a result of gradual geographical (allopatrial) speciation (consequently, these are subspecies in a common sense, but not only). Moreover, semispecies are also a result of hybridization in conditions of incomplete isolation of hybrid races in the case of sympatrial speciation. Semispecies appeared earlier in Grant’s works than in K. M. Zavadsky’s. The greatest crossing systems in a group of hybridogenous species Grant considered “syngameons”. He pointed out that they differ from a natural species inthat they have a more complicated inner structure, and in the hierarchy of taxonomic categories, they have a status of series or sections [why not genera and, in some cases – groups of genera? – R. K.].
Among species-like natural complexes V. Grant distinguishes especially homogamous complexes, the main peculiarity of which is that hybrid individuals and races which constitute such a complexes possess the same complete (unlimited) ability to recombine genes, as parental species have. Grant supposes races in these complexes, as well as “twin-species” in polyploid complexes, to be equal to biological species, and, being an adherent of “reticulate evolution”, gives an important role in evolution to homogenous hybrid complexes. But he, of course, distinguishes from species heterogenous hybrid complexes, part of polyploid complexes and agamic complexes. As A. L. Takhtajan points out in the editor’s foreword in the first translation of Grant’s book, Grant isn’t aware of Russian-language literature, for he read neither N. I. Vavilov, nor V. L. Komarov; I can add that he, surely, also doesn’t know M. G. Popov and S. V. Yuzepchuk. But it is important that general direction of his search is next to ideas considered for a long time in Russian-language systematics of plants, and it’s pleasing to realize, that in many cases these ideas appeared in our literature much earlier than abroad. It seems, therefore, to be appropriate to sum up in several theses the results of this development of ideas of systematics of plants both in Russian-language literature and abroad:
1) In the evolution of plants, in addition to divergent microevolution, microevolutional processes connected with hybridization and polyploidy, play a great role. These are much more developed in higher plants than in higher animals.
2) Elementary evolutive units in plants at the stage of adaptive divergence are both monospecies and mixed (two-polyspecies) populations. The action of selection in these populations either increases or decreases as a result of early development of isolating mechanisms, which, however, do not provide complete isolation of individuals or groups of individuals. Further stages of adaptive radiation of changed forms of plants run not only in conditions of interaction with different populations of another species, but also against a background of permanent hybrid changes both in populations of species separated elsewhere, yet enough, and in populations constituted by a complex of races not yet separated completely from each other, but, however, not presented a single species.
3) In the final stages of speciation of plants we also deal not only with a single separated species but also with complexes of races of different degree of separation (species, subspecies, microspecies). These complexes are to the same degree perspective regarding further evolution as any other widespread and separated species.
V. L. Komarov, and much later V. Grant, consider non-species complexes of races (and microraces) as formations living for a shorter time than species. It should be noticed, however, that this fact is not proved and, moreover, there are a lot of facts proving the contrary. Syngameons, comprising numerous species of any genus (for instance, Aquilegia) or several groups of diverse genera (in subfamilies Maloideae and Prunoideae of fam. Rosaceae), crossing permanently when widening of limits of certain species with different related species, can’t be considered as young groups originating, perhaps, from a single species. Numerous genera of Gramineae have hybridogenous origin, and not rarely it is possible to propose that they descended most probably from a complex of races initially diverse in genomes. A lot of ancient polyploid (or polyploid of high levels of ploidy, stabilized by aneuploid diminution) groups in such a genera, for example, Magnolia, Talauma, Populus, Platanus, have not finished their evolution because each of these contains a considerable number of young hybridogenous races. That is why we have no reason to suppose that hybridization definitely leads to the effect of a “converging funnel”, which is peculiar to hybridization between closely related forms. Meanwhile, exact hybridization of closely related races is often difficult (these races, as a rule, have different isolating mechanisms and, moreover, are also often isolated geographically). On the contrary, hybridization between non-closely related species of plants is always more productive, despite of sympatrial character of their evolution together with the parental species. But, it is clear, that in this case hybridization in some groups is usual, whereas in others exceptionally rare.
How is it possible to demonstrate this diversity of natural evolutive units in a hierarchic system of taxa, which is, essentially, a task of floristic revisions?
The “International Code of Botanical Nomenclature”, which sets the rules for the naming taxa and the hierarchy of a system, suggests a spesies as the only one basic taxon in this hierarchy. Number of above-species taxa, permitted for use, is considerably higher than of subspecies rank. In this hierarchy it is more logical to accept a species as a narrowly understandable and rather well separated (isolated) natural race, i. e. as determined by the ecological-geographic-morphological method of systematics. A great number of the above-species taxa reflect, in this case, a degree of divergence (hiatus) among species, proposed to any degree to be relatives, and in this degree of divergence also, in some measure, – stages of the evolutional development of plants. Strictly speaking, this applies only in an ideal scheme (in a line of monotypic taxa: monotypic species is a species of monotypic genus, of monotypic family, etc.). In any other case, the stages of evolution of plants can be displayed only by the whole compound of a line of included into each other groups in a world flora, ranged in a hierarchy of taxa. This greatly increases a subjective part in an estimation of changes of morphome in phylums of plants, known in most of these cases only by a contemporary species. But, I’m sure that this estimation of phylogenesis in stages of evolution of all the plants, reflected in the hierarchy of taxa, is not a task of floristic revisions. These revisions can reflect only types of evolutionary changes of contemporary groups of species, which are diverse in different groups. Multi-stage hierarchy of above-species taxa is of little use for this purpose; it was demonstrated by experience of its application for the construction of evolutionary lines of taxa connected with each other – species and series as a lowest above-species taxonomic category. In the hierarchy of taxa the construction of evolutionary lines runs “up from the bottom” (from the basis of a phylogenetic tree) and this is formed, undoubtedly, typologically (from a maximally generalized type to an increasing concrete type, approaching to natural races). But according to the logic of ecological-geographic-morphological method (in V. L. Komarov’s interpretation), construction of the evolutionary lines starts from a species (from species-race to preceding in time a stage of evolution, both divergent and reticulate, and then, to the further stages, if this is possible). In this case, typological generalization in a pure form is impossible, because the greater part of fossilized forms are unknown. Generalization must be based here not only on characteristics of morphome, but also on features of biont in the sense of S. I. Korshinsky, i. e. on the totality of ecologically-physiological and biological characteristics in groups of species and (or) on molecular-biochechemical characteristics of genome changes (in a line from species-race – to a group of closely related species – to a species of one genus, etc., but not on the contrary). In a hierarchy of intraspecific taxa we to the some degree can imagine a structure of populational diversity of species, reflecting, of course, microevolutionary processes running in populations, but turning into one or another evolutionary phenomenon just during a rather long time. Thus, taxon “forma” can be treated as a minimal taxa of intraspecific classification applying mainly to phenomena of indeterminate variability (indigested demonstration of characteristics of phenotype as a result of change of frequence of appearance of mutations on one or several loci).
Most ordered changes of frequence of alleles (and, consequently, of characteristics of phenotype) present changes in geographical gradient. When these changes are relatively gradual, i. e. panmictic connection of populations is provided, we deal with clinal variability (cline). But in most cases we observe interrupted changes of phenotypes, connected rather often with differences in ecotopes. These are separated under conditions of altitudinal zonality races of different Euroasian species of Solidago in Khibines and Altai and also appearing simultaneously in Asian mountains races of different species of Achillea (including Ptarmica). Even if we can find in the belt of contact of these races with parental species intermediate forms, we are entitled to treat them as an independent evolutive units. And even if under equal cultural conditions they demonstrate in many features a return to initial types, it means no more than that these races are quite young and yet poorly fixed by natural selection. In the case of disjunction of area of distibution of widespread species on plains we often observe the same race formation. These are Hepatica nobilis and H. asiatica, Convallaria majalis and C. keiskei, etc. But in the case of development of disjunctive vicarial races, connected with also disjunctive separation of hybridogenous complex among them, we see more isolated (separated) races. These are races of affinity of Anemone ranunculoides, A. coerulea and hybridogenous A. uralensis. All these examples present variants of contemporary (relatively) race formation. In the hierarchy of taxonomic units we can call less separated races a subspecies, more separated – young (both divergenty separated and hybridogenous) species. Applying such a hierarchy of taxa (form – subspecies – species) we have a chance to avoid use of such an indefinite taxon as “variety” (varietas), in complete accordance with Ch. Darwin, who accepted it in a common sense, close to unranged “race” in Russian-language botany or “Sippe” – in German literature. As we know, S. I. Korshinsky did so.
The main result of the aforesaid regarding the reflection in floristic revisions of diversity of evolutionary processes in the plant world is a necessity of division of methods of description of evolutive natural units on the level of intraspecific and interspecific processes. Intraspecific processes can be reflected in some hierarchy of taxa, but on the level higher than of a species, these processes (not their results) themselves can’t be expressed in this taxonomic hierarchy. But they can and must be expressed in floristic revisions in some other way.
Such an intraspecific taxa as forma and subspecies are quite enough for objective reflection in revisions of different cases of indefinite (populational) variability, on the one hand, and ordered, definite ecologically-geographical (interpopulational) variability, on the other hand. More detailed characteristics in this case can be done in notes. Species, independent of their path of formation and degree of separation from each other, present a single basic taxon in floristic revisions. Some specificity of speciation also can be marked in notes, for example: clonal species, saltatory (or strongly separated) species, hybridogenous species, compiled species, etc.
It is the most important in floristic revisions to demonstrate namely the diversity of the above-species evolutionary units and interspecific (and inter-race) complexes. It’s better to point out in special notes in characteristics of genera as well as in characteristics of species constituting any complex. It is quite acceptable to apply series – the least above-species taxon of hierarchy of systematic units – to emphasize the closest affinity of two-several species, but it should be noticed in this case, if we deal with a part of evolutionary series (line) of species, one of which is an ancestral in regard to other(s), or with a bunch of closely related species, a supposed ancestor of which is an extinct species. But, to be repeated, none monotypic series can be accepted. It’s possible (in some situations even necessary) to point out in a different way the introgressive-interspecific complexes of hybrid forms, races, species (not complicated by formation of apomictic races), hybrid-clonal complexes with facultative apomixis (cycles of races or species with incomplete separation of apomictic races – “microspecies”), hybrid-polyploid complexes of races (in fact, of twin-species with facultative hybridization), gregarious complexes of species with obligatoty unpaired polyploidy, gregarious complexes with aneuploidy, gregarious complexes with agamatoploidy, hybrid swarms, above-species syngameons, and also other, less distributed types of evolutionaty interspecific structures, for instance, gregarious complexes with aneuploidy, complicated by permanent vegetative propagation – cloning of different cytotypes (in species of Cardamine, etc.), heterogamous complexes with obligatory heterozygosity in translocations (with coiled chromosomes) for races of the genus Oenothera, agamospermous diasporal complexes of races in some groups of Hieracium, etc.
It’s not correct to suppose that all this is of a theoretical importance only, in particular, for the purposes of the analysis of floras. It has also great value for the practice of rational use and protection of species, introduction and selection of them (Kamelin, 1997).
Some notes on the genera of plants. Genera of plants as a degree of evolutionary changes in one or another group of plants present, of course, a real natural phenomena. It’s quite clear, however, that the age of a genera is much greater than of the species constituting them. Genera distinguished by scientists, contain also many fossilized species including ones unknown to us, which were in different ways connected with surviving species. This is exactly the evolutionary meaning of the term “genus”, this is a position of a genus in a logical system of hierarchy of ranged taxa, accepted by systematists. It’s evident to every botanist who has managed to compare elsewhere two-several systems of the same group of plants revised by different monographists, that plant genera present a subjective concept in any constructions of systematists, as it were their “handwork”. A genus remains a subjective concept because of the objective, in point of fact, gnoseological reasons. We don’t know not only all the species of practically every genus on Earth (part of them are extinct), but also aren’t aware of the previous types of speciation which both lead to the separation of any genus (seeming to us separated) and taking place within the limits of this once isolated phylum. This is exactly why, in particular, we have no hopes that molecular or precise biochemical methods can provide us with absolute criteria for the differentiation of genera. The only thing they can give us (and yet give) is the assurance that many of present-day genera are a result of not only definite divergence but also perforated evolution. In connection with the above mentioned we should not break too hastily with traditional systems of genera, even in well studied families. Both volume and limits of genera are subjective, but they will not become more objective (more logically valid) in the case of consecutive application of both enlargement and parcelling of genera. In the case of parcelling of large genera we also obtain a less visible system of taxa. Even in rather poor (for such spacious territory) flora of Russia just double increase of a number of genera will make it quite impossible a training of specialists-systematists (not to mention non-systematists) for in this case there should be distinguished more than 2000 genera (in approximately 190 families, most of which are absent in the courses of systematics!). Meanwhile, such an increase in the number of genera can be easely forecasted when analysing the latest tendencies of parcelling of genera, especially apparent in the Russian-language systematics of flowering plants. Thus, in the family Fabaceae, in general poorly presented by genera on the territory of Russia, 13 genera, accepted in S. K. Cherepanov’s check list (1995), present a result of strict interpretation of genera in the tribe Trifolieae, and another 7 genera of the same tribe (some of which have now been distinguished in regional revisions on Russia) to some degree are also accepted in systems of different specialists in this group. At the same time large polymorphic genera Astragalus (except the stillborn genus Astracantha, also accepted by S. K. Cherepanov) or Vicia, weren’t exposed to such a division.
Therefore it’s meaningless to considerably change a system of traditional genera in revisions dealing with the flora of Russia, especially if it’s possible to use completely the capabilities of reflection of main intraspecific taxa – subgenera and sections.
R. V. Kamelin