The study of Arctic life, one may fairly say, has only just started and is at present in the initial stage of recording and listing the population. Especially incomplete is our knowledge of the terrestrial and freshwater invertebrate fauna, in which the insects undoubtedly occupy the first place as regards number of species. The Soviet and former Russian literature contains no general list of the Arctic fauna, whilst European compendiums are far from being complete or perfect.
The term Arctic Region is variously interpreted. The most natural is to consider it as the complex of territories occupied by the tundra and forest-tundra, including in the latter the northern depressed forest belt of the taiga zone. (Pages 1 to 3 of the Russian text).
Arctic plant life is distinguished by its more or less developed tundra character and the prevalence in it, parallel with the lichens and mosses, of low shrubs and perennials with a short vegetative period. It is related to the highland type of vegetation, and also to that of swamps and forests Its affinities with steppe and highland-steppe forms are also indisputable. Tundra flora presents a greatly impoverished formation of the arcto-tertiary flora and is the result of the metamorphosis of northern tertiary vegeta tion. It still persists up to the highest latitudes, even up to the socalled ice-zone of the Arctic. (Pages 4 and 5 of the Russian text).
We have no general characteristic of the Arctic fauna. It is usually described as an impoverished palaearctic fauna of recent, postglacial origin. After our present, extremely incomplete data the terrestrial, and in part the freshwater, population of the Arctic already numbers five and a half thousand species. The actual number of existing Arctic species may cer tainly be estimated as being at least three times greater. (Pages 4 to 7 of the Russian text).
The Arctic region of Eurasia contains about 10 species of terrestrial mammals. This number is too insignificant to permit of any conclusions as to their origin. The affinities of the arctic fox and of the five species of Lemmus do not exclude the possibility of their origin lying in southern Siberia or Central Asia. The reindeer belongs, more probably, to the group of migrants from America. The number of resident birds actually proper to the Eurasian Arctic is also very small, not over 7 or 8 species. The re maining mass of birds, visiting the Arctic for the very short summer sea son, yields to zoogeographical analysis with the greatest difficulty only. Some ornithologists are inclined to ascribe the historical origin and for mation of the bird fauna of the Arctic to the extreme north-oastorn region of present Asia and to the hypothetical Beringia, without forgetting the affinities of the avifauna with the bird population of southornSiberia and Central Asia. Reptiles and amphibians are practically absent from the Arc tio. Freshwater fishes are represented by a very small number of species, which is especially restricted in the basins of west-siberian rivers. The fauna of the freshwater and terrestrial molluscs of the Eurasian Arctic has been very insufficiently studied. It can, however, be said to be in state, of undoubted depression. (Pages 6 to 11 of the Russian text).
The insects are represented in the Arctic by a large and varied num ber of species. Especially well represented are the orders of Diptera, Hymenoptera, Coleoptera and Lepidoptera. They include many euarctic spe cies, i. e. species occurring exclusively in Arctic latitudes, even on the most inhospitable islands of the Arctic ocean, and not to be found else where. Parasitic forms numerically predominate among the Hymenoptera whilst the groups of bees and ants, excepting the bumble-bees, are feebly represented. The beetles are mainly carnivorous groups. The specific com position of the Lepidoptera is very considerable and includes many euarctics. By composition and origin the fauna of Lepidoptera shows affinities with the temperate countries of eastern Siberia, Mongolia, northern China, and, possibly, further southwards to Tibet, i. e. to the ancient Angara shield of the primary uplift of Asia. The Hemiptera and Orthoptera are very scarce in the Arctic, whore the conditions are just within the boundary of possible existence for them. The orders associated with fresh water, espe cially the Odonata, are also poorly represented, but they have been too little studied as yet. The Collembolan fauna is, on the contrary, rich in forms, and its further study will undoubtedly furnish valuable zoogeographical conclusions. The same applies to the fauna of Araneina of the Eura sian Arctic, which comprises a large number of endemic species (Pages 11 to 17 of the Russian text).
Of other groups of terrestrial and freshwater invertebrates, insuffi ciently studied in general, we must note the Oligochaeta and the Rotifera, with a large number of species, hardly comprising any endemic forms, and the Turbellaria especially, giving a long list of species, among which there is, on the contrary, a conspicuous number of euractics. The further zoogeographical study of the last group promises decisive data for the characteristic and history of the Arctic fauna. (Pages 17 to 19 of the Russian text).
The existence of the Arctic fauna under the climatic and landscape conditions prevailing in high latitudes undoubtedly indicates a long adap tation to them. The question, however, of whether the Arctic fauna is a spe cial tundra fauna must be answered in the negative: the physiological mechanism of the above mentioned adaptation is not known and is, evi dently, not the same in different forms; the physiological and ecological data, now in hand are limited to primary statements of most elementary obser vations. One point only is more or less certain: that the thermal conditions in the Arctic are nowise the original cause of the composition of its fauna, for this composition depends primarily on biocoenotic nutrition relations, which are based on plant life with its main dependence on conditions of light. It is neither possible to unite the Arctic fauna into one ecologioal whole, nor to identify it terminologically with the tundra fauna. No speci fic peculiarities, common to the whole faunal complex of the Arctic as the result of adaptation to Arctic conditions, have as yet been physiologically established, and such peculiarities can hardly exist. Ecological analysis at its present stage gives no support whatever for assuming the real existence of such particularities. (Pages 19 to 27 of the Russian text).
As for the next question of whether the Arctic fauna, at least in part, presents a certain unity which may be expressed in taxonomic conceptions, in other words, of whether it contains traces of group adaptations to the specific conditions of the Arctic, - the only answer is again in the nega tive. The Arctic fauna is taxonomically most heterogeneous and includes in all its divisions generalized or primitive groups alongside specialized or higher ones. Cases of the predominance of some or other systematic groups are preeminently due to ecological nutrition relations. And there is not a single systematic group of animals which would pretend to be a special product of adaptation to Arctic conditions. The complexity of the Arctic fauna is only an evidence of its being the remnant of former hete rogeneity. (Pages 28 and 29 of the Russian text).
The geographical, statistical and geologo-historical methods, remaining at the disposal of the investigator, are at present, with the addition of all ecological and biocoenological considerations, the only means of solving the problem of the composition and origin of the Arctic fauna. The almost complete absence of palaeontological material on Arctic invertebrates is, however, a very great barrier for the wide application of historical data. (Pages 29 to 31 of the Russian text).
The age and origin of the Arctic tundra landscape have been variously described. The participation of the factors of cooling and glaciation in its formation is, nevertheless, indisputable. It is, however, hardly possible to ascribe to the tundra landscape a young age and a postglacial origin. Each of its types of vegetation shows relationship with the corresponding tertiary type. The wide circumpolar distribution of the biocoenoses of the tundra landscape also supports the idea of its considerable antiquity and points to the beginning of its formation lying in the pliocene or in the early part of the quaternary, in the northern regions of the Angara continent.
The present and past connections of the tundra landscape with others are varied and not restricted to the present predominant contact of the tundra with the taiga forest. It is possible to assume that in the past - especially in the postglacial xerothermic period - there was a much more close connection between the tundra and the steppe than now. The former existence of a cold, tundra-like steppe may also be presumed. The compa rison of the Arctic fauna with the boreo-alpine fauna of mountain landsca pes is more common in the literature, although the ecological and climatic similarities between these two landscapes are far from being as actual as was believed. The biooomplexes of mountain landscapes are, moreover, not autochthonous at all, but complicated and heterogeneous by origin; so that they themselves need separation into their primary components.
On the other hand, it is quite indisputable, that the recent Arctic fauna is, first of all, the result of quaternary glaciation, which shifted the climatic and, parallel with them, the biological zones of the northern hemi sphere. The hypothesis of the Earth having passed through a period of absence of zonation remains unproved; but the stability of climatic zones is just as hypothetical. Of all the theories proposed for explaining the shif ting of climatic zones, and especially of such repeated shiftings, the most acceptable, from a biogeographer's standpoint, is the theory of horizontal displacements of continental masses and, consequently, of the oscillations of the poles caused by disturbances of equilibrium through the accumula tion of ice-caps at the poles. In addition to latitudinal shifts there undoubt edly also existed shifts both in the meridional direction and at different angles to it. It is also possible to assume a progression of glacial phenomena in a general west to east direction. (Pages 31 to 41 of the Russian text).
The existence of Arctic endemics - "euarctics" - now living under Arctic conditions only, raises the question of the possibility of the part of the preglacial fauna surviving the glacial age in the regions of glaciation. It is more than probable that the Arctic fauna does not represent the re sult of postglacial remigration only. The partial recognition of this possi bility is well known and follows, by the way, from a feeling of distrust in the existing reconstructions of climatic and ecological pictures of the gla cial epochs, the correctness of which is far from certain and which may, perhaps, be greatly overrated as regards severity. The Arctic fauna is, to a considerable extent, the relics of the ancient glacial and even preglacial fauna. The fauna of Arctic islands is especially interesting, as the euarctics occurring on them have most rights to be considered just such relics of preglacial times owing to their insular isolation and to the impossibility of ascribing an inverse postglacial remigration from the mainlands. (Pages 41 to 45 of the Russian text).
The majority of bioelements were during glaciations driven to one side and mechanically shifted to the places of refuge, whence, on the ter mination of the Ice Ages, there began a return invasion or remigration back to the territories freed from their ice-cover. The main region of remigrational invasions is now covered by taiga. The complicated pictures of retreats to the places of refuge and of return invasions which were super imposed one on the other during all the known glacial and interglacial periods in Europe and Asia will hardly ever be fully unravelled. The usual divisions of the European Ice Age, which are at present difficult to syn chronize, the as yet unreliable divisions of the Asiatic Ice Age, are of no assistance to us. The study of these movements as well as the establishment of the boundaries of the ice-sheets, is indirectly possible by means of analyzing the phenomena of the discontinuous distribution of the faunal and floral elements of Europe and the temperate regions of Asia. (Pages 45 to 48 of the Russian text).
The main refuge regions for preglacial life were, probably, transal pine South Europe and Western Asia in the west; East China, Manchuria and Japan in the east; the Turanian-Iran region in the south; and likewise the lands of the primordial Angara massif. Precise locations of the lands of refuge and of the intervals in the areas of preglacial discontinuous distribution will permit in the future of a rational division of the Holarctic region and to reconstruct a picture of the latest glacial phenomena at least. But this task is extremely complicated by the difficulty of synchroni zing these phenomena in the various regions of the Holarctic and by their probable asynchronism following from the theory of the shifting of the poles in conjunction with the assumption of the progression of glacial phenomena from west to east. (Pages 49 to 55 of the Russian text).
As regards the historical affinities and, consequently, the origin of the Arctic fauna, it is, first, necessary to discard the a priori and simplified current conceptions of this fauna as, on the one hand, of an impoverished, derivate of the Palaearctic, or, more generally, of the Holarctic fauna; and on the other, as of an autonomous region, equivalent to other generally recognized regions. There are, likewise, no foundations for the attempts of deriving it from the north, from hypothetical lands lying at the northpole. The composition of the Arctic fauna, notwithstanding its very consi derable number of endemics or euarctics, discloses its ancient origin and permits of its division into four components: European, West- and East-Siberian, and the entirely uninvestigated Tshukotka-Anadyr one, with an especially distinct boundary along the basin of Enisei and with a well marked interval occupying west Siberia up to Enisei. This interval may be due to late tertiary or quaternary southward transgression of the Arctic ocean and to extensive west-siberian glaciations. The hypothesis assuming- the place of origin and formation of the Arctic fauna to be the extremenorth-east of Asia and problematic Beringia, is based on faunistic material of vertebrates exlusively, and of birds preeminently. It is, thus, onesided, though in general it does not contradict the hypothesis, accepted by wri ter of this paper and deriving the Arctic fauna from the much less pro blematic ancient Angara plateau, now occupied by the southern part of cen tral Siberia, the Baikalian countries, the Amur province till Mongolia, and. China till north Tibet. (Pages 55 to 57 of the Russian text).
By means of cartographical and taxonomical data can be established, in particular, the affinities of the Arctic Lepidoptera from the distant Euro pean west and from the distant Asiatic east, and likewise from the extreme north-west of North America, with those of the above mentioned Angara centre. This conclusion can be confirmed by similar data on the faunae of mammals, birds, beetles and Trichoptera, and likewise by studies of the flora. The idea of miocene glaciation in east Siberia is also favourable to the hypothesis of the Angara origin of the Arctic fauna, as it explains the complete absence of tropical elements from this fauna and allows it to be considered as being psychrophilous from the earliest times. The extension of the hypothesis of the Angara origin to the entire European or Palaearc tic, or even to the entire Holarctic region, is a considerable exaggera tion. This hypothesis cannot be primarily accepted as the very conception of the Palaearctic and the Holarctic regions is to a considerable extent formal and, therefore, the composition of the faunae of these regions must itself be first deciphered and described. (Pages 58 to 62 of the Russsian text).
One of the main problems connected with the origin of the Arctic fauna is that of the euarctics and their genesis. As far as Lepidoptera are concerned, the systematic analysis of euarctic forms of this order points to their pre-eminently Angara origin and to their primordial autochthony in the Arctic regions occupied by them, due to their surviving glacial condi tions of existence on the spot. (Pages 63 to 65 of the Russian text).
It must be emphasized in conclusion that the above mentioned hetero geneity of the Palaearctic and Holarctic regions is beginning to be reco gnized in last years by many zoogeographers, and that it is, therefore, neces sary to start a revision of current biogeographical conceptions on a ratio nal basis of wide ecologico-biocoenological and historico-geological investi gations. Such a revision must be accompanied by the introduction of a new and more rational terminology. We already have successful attempts in this direction, in particular in the domain of the Soviet zoogeography likewise. (Pages 66 and 67 of the Russian text).
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